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Aims: Accumulating evidence indicates the involvement of TRESK potassium channels in migraine, however, effects of TRESK activation on migraine-related mechanisms remain unclear. We explored effects of TRESK channel modulation on migraine-related behavioral and molecular markers in in-vivo and ex-vivo rat models of migraine., Main Methods: The selective TRESK activator cloxyquin at different doses, the TRESK inhibitor A2764, and the migraine drug sumatriptan were tested alone or in different combinations in nitroglycerin (NTG)-induced in-vivo model, and in ex-vivo meningeal, trigeminal ganglion and brainstem preparations in which CGRP release was induced by capsaicin. Mechanical allodynia, CGRP and c-fos levels in trigeminovascular structures and meningeal mast cells were evaluated., Key Findings: Cloxyquin attenuated NTG-induced mechanical allodynia, brainstem c-fos and CGRP levels, trigeminal ganglion CGRP levels and meningeal mast cell degranulation and number, in-vivo. It also diminished capsaicin-induced CGRP release from ex-vivo meningeal, trigeminal ganglion and brainstem preparations. Specific TRESK inhibitor A2764 abolished all effects of cloxyquin in in-vivo and ex-vivo. Combining cloxyquin and sumatriptan exerted a synergistic effect ex-vivo, but not in-vivo., Significance: Our findings provide the experimental evidence for the anti-migraine effect of TRESK activation in migraine-like conditions. The modulation of TRESK channels may therefore be an attractive alternative strategy to relieve migraine pain., Competing Interests: Declaration of competing interest The authors declared that they have no potential conflicts of interest., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Sleep disturbances and persistent pain conditions are public health challenges worldwide. Although it is well-known that sleep deficit increases pain sensitivity, the underlying mechanisms remain elusive. We have recently demonstrated the involvement of nucleus accumbens (NAc) and anterior cingulate cortex (ACC) in the pronociceptive effect of sleep restriction. In this study, we found that sleep restriction increases c-Fos expression in NAc and ACC, suggesting hyperactivation of these regions during prolonged wakefulness in male Wistar rats. Blocking adenosine A 2A receptors in the NAc or GABA A receptors in the ventral tegmental area (VTA), dorsal raphe nucleus (DRN), or locus coeruleus (LC) effectively mitigated the pronociceptive effect of sleep restriction. In contrast, the blockade of GABA A receptors in each of these nuclei only transiently reduced carrageenan-induced hyperalgesia. Pharmacological activation of dopamine D 2 , serotonin 5-HT 1A and noradrenaline alpha-2 receptors within the ACC also prevented the pronociceptive effect of sleep restriction. While pharmacological inhibition of these same monoaminergic receptors in the ACC restored the pronociceptive effect which had been prevented by the GABAergic disinhibition of the of the VTA, DRN or LC. Overall, these findings suggest that the pronociceptive effect of sleep restriction relies on increased adenosinergic activity on NAc, heightened GABAergic activity in VTA, DRN, and LC, and reduced inhibitory monoaminergic activity on ACC. These findings advance our understanding of the interplay between sleep and pain, shedding light on potential NAc-brainstem-ACC mechanisms that could mediate increased pain sensitivity under conditions of sleep impairment., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier Ltd.)

The gut microbiota produces metabolites that enrich the host metabolome and play a part in host physiology, including brain functions. Yet the biological mediators of this gut-brain signal transduction remain largely unknown. In this study, the possible role of the gut microbiota metabolite indole, originating from tryptophan, was investigated. Oral administration of indole to simulate microbial overproduction of this compound in the gut consistently led to impaired locomotion and anxiety-like behaviour in both C3H/HeN and C57BL/6J mice. By employing c-Fos protein expression mapping in mice, we observed a noticeable increase in brain activation within the dorsal motor nucleus of the vagus nerve (DMX) and the locus coeruleus (LC) regions in a dose-dependent manner. Further immune co-labelling experiments elucidated that the primary cells activated within the LC were tyrosine hydroxylase positive. To delve deeper into the mechanistic aspects, we conducted chemogenetic activation experiments on LC norepinephrine neurons with two doses of clozapine N-oxide (CNO). Low dose of CNO at 0.5 mg/kg induced no change in locomotion but anxiety-like behaviour, while high dose of CNO at 2 mg/kg resulted in locomotion impairment and anxiety-like behaviour. These findings support the neuroactive roles of indole in mediating gut-brain communication. It also highlights the LC as a novel hub in the gut-brain axis, encouraging further investigations., Competing Interests: Declaration of competing interest The authors declare no competing interests., (Copyright © 2024. Published by Elsevier Inc.)

Background and Purpose: The first randomized placebo-controlled therapeutic trial in radiologically isolated syndrome (RIS), ARISE, demonstrated that treatment with dimethyl fumarate (DMF) delayed the onset of a first clinical event related to CNS demyelination and was associated with a significant reduction in new and/or newly enlarging T2-weighted hyperintense lesions. The purpose of this study was to explore the effect of DMF on volumetric measures, including whole brain, thalamic, and subcortical gray matter volumes, brainstem and upper cervical spine three-dimensional (3D) volumes, and brainstem and upper cervical spine surface characteristics., Methods: Standardized 3T MRIs including 3D isotropic T1-weighted gradient echo images were acquired at baseline and end-of-study according to the ARISE study protocol. The acquired data were analyzed using Structural Image Evaluation Using Normalization of Atrophy (SIENA), FreeSurfer v7.3, and an in-house pipeline for 3D conformational metrics. Multivariate mixed models for repeated measures were used to analyze rates of change in whole brain, thalamic, subcortical gray matter, as well as change in the 3D surface curvature of the dorsal pons and dorsal medulla and 3D volume change at the medulla-upper cervical spinal cord., Results: The study population consisted of 64 RIS subjects (DMF:30, placebo:34). No significant difference was seen in whole brain, thalamic, or subcortical gray matter volumes in treated vs. untreated RIS patients. A significant difference was observed in dorsal pons curvature with the DMF group having a lower least squares mean change of - 4.46 (standard estimate (SE): 3.77) when compared to placebo [6.94 (3.71)] (p = 0.036). In individuals that experienced a first clinical event, a greater reduction in medulla-upper cervical spinal cord volume (p = 0.044) and a decrease in surface curvature was observed at the dorsal medulla (p = 0.009) but not at the dorsal pons (p = 0.443)., Conclusions: The benefit of disease-modifying therapy in RIS may extend to CNS structures impacted by neurodegeneration that is below the resolution of conventional volumetric measures., (© 2024. Springer-Verlag GmbH Germany, part of Springer Nature.)

All terrestrial vertebrate life must transition from aquatic gas exchange in the embryonic environment to aerial or pulmonary respiration at birth. In addition to being able to breathe air, neonates must possess functional sensory feedback systems for maintaining acid-base balance. Respiratory neurons in the brainstem act as pH sensors that can adjust breathing to regulate systemic pH. The central pH sensitivity of breathing-related motor output develops over the embryonic period in the zebra finch (Taeniopygia guttata). Due to the key role of chloride ions in electrochemical stability and developmental plasticity, we tested chloride's role in the development of central pH sensitivity. We blocked gamma-aminobutyric acid-A receptors and cation-chloride cotransport that subtly modulated the low-pH effects on early breathing biorhythms. Further, chloride-free artificial cerebrospinal fluid altered the pattern and timing of breathing biorhythms and blocked the stimulating effect of acidosis in E12-14 brainstems. Early and middle stage embryos exhibited rebound plasticity in brainstem motor outputs during low-pH treatment, which was eliminated by chloride-free solution. Results show that chloride modulates low-pH sensitivity and rebound plasticity in the zebra finch embryonic brainstem, but work is needed to determine the cellular and circuit mechanisms that control functional chloride balance during acid-base disturbances., (© 2024 Wiley Periodicals LLC.)

Obesity has been associated with a chronic increase in sympathetic nerve activity, which can lead to hypertension and other cardiovascular diseases. Preliminary studies from our lab found that oxidative stress and neuroinflammation in the brainstem contribute to sympathetic overactivity in high-fat-diet-induced obese mice. However, with glial cells emerging as significant contributors to various physiological processes, their role in causing these changes in obesity remains unknown. In this study, we wanted to determine the role of palmitic acid, a major form of saturated fatty acid in the high-fat diet, in regulating sympathetic outflow. Human brainstem astrocytes (HBAs) were used as a cell culture model since astrocytes are the most abundant glial cells and are more closely associated with the regulation of neurons and, hence, sympathetic nerve activity. In the current study, we hypothesized that palmitic acid-mediated oxidative stress induces senescence and downregulates glutamate reuptake transporters in HBAs. HBAs were treated with palmitic acid (25 μM for 24 h) in three separate experiments. After the treatment period, the cells were collected for gene expression and protein analysis. Our results showed that palmitic acid treatment led to a significant increase in the mRNA expression of oxidative stress markers (NQO1, SOD2, and CAT), cellular senescence markers (p21 and p53), SASP factors (TNFα, IL-6, MCP-1, and CXCL10), and a downregulation in the expression of glutamate reuptake transporters (EAAT1 and EAAT2) in the HBAs. Protein levels of Gamma H2AX, p16, and p21 were also significantly upregulated in the treatment group compared to the control. Our results showed that palmitic acid increased oxidative stress, DNA damage, cellular senescence, and SASP factors, and downregulated the expression of glutamate reuptake transporters in HBAs. These findings suggest the possibility of excitotoxicity in the neurons of the brainstem, sympathoexcitation, and increased risk for cardiovascular diseases in obesity.

Cerebellar ataxia is a heterogeneous group of neural disorders clinically characterized by cerebellar dysfunction. The diagnosis of patients with progressive cerebellar ataxia is complex due to the direct correlation with other neuron diseases. Although there is still no cure for this pathological condition, some metabolic, hereditary, inflammatory, and immunological factors affecting cerebellar ataxia are being studied and may become therapeutic targets. Advances in studying the neuroanatomy, pathophysiology, and molecular biology of the cerebellum (CE) contribute to a better understanding of the mechanisms behind the development of this disorder. In this study, Wistar rats aged 30 to 35 days were injected intraperitoneally with 3-acetylpyridine (3-AP) and/or metformin (for AMP-activated protein kinase (AMPK) enzyme activation) and euthanized in 24 hours and 4 days after injection. We analyzed the neuromodulatory role of the AMPK on cerebellar ataxia induced by the neurotoxin 3-AP in the brain stem (BS) and CE, after pre-treatment for 7 and 15 days with metformin, a pharmacological indirect activator of AMPK. The results shown here suggest that AMPK activation in the BS and CE leads to a significant reduction in neuroinflammation in these regions. AMPK was able to restore the changes in fatty acid composition and pro-inflammatory cytokines caused by 3-AP, suggesting that the action of AMPK seems to result in a possible neuroprotection on the cerebellar ataxia model., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are involved in the control of horizontal and vertical gaze, respectively. A previous study showed that PHN neurons exhibit depolarized or hyperpolarized responses to noradrenaline (NA). However, the adrenoceptor types that participate in NA-induced responses and the effects of NA on INC neurons have not yet been investigated. Furthermore, the relationship between NA-induced responses and neuron types defined by neurotransmitter phenotypes has not been determined. In this study, we investigated NA-induced current responses in PHN and INC neurons and the relationships between these responses and neuron types using whole cell recordings in wild-type and transgenic rat brainstem slices. Local application of NA to the cell soma induced slow inward (SI) and slow outward (SO) currents that were mainly mediated by α1 and α2 adrenoceptors, respectively. These current responses were observed in both PHN and INC neurons, although the proportion of INC neurons that responded to NA was low. Analyses of the distributions of the current responses revealed that in the PHN, all fluorescently identified inhibitory neurons exhibited SI currents, whereas glutamatergic and cholinergic neurons exhibited both SI and SO currents. In the INC, glutamatergic and inhibitory neurons preferentially exhibited SI and SO currents, respectively. When the PHN and INC neurons were characterized by their firing pattern, we found that the proportions of the currents depended on their firing pattern. These results suggest that various modes of noradrenergic modulation in horizontal and vertical neural integrators are dependent on neuron type. NEW & NOTEWORTHY Noradrenergic modulation of oculomotor neural integrators involved in gaze control has not been elucidated. Here, we report that noradrenaline (NA)-induced slow inward (SI) and outward (SO) currents are mediated mainly by α1 and α2 adrenoceptors in neurons that participate in horizontal and vertical gaze control. The NA-induced current responses differed depending on the neurotransmitter phenotype and firing pattern. These results suggest various modes of noradrenergic modulation in horizontal and vertical integrator neurons.

Introduction: Tacrolimus-associated neurotoxicity (TAN) manifests with wide clinical spectrum, ranging from mild tremors to severe encephalopathy. The isolated involvement of the brainstem is a rarely documented presentation of TAN, and its clinical and diagnostic characteristics are unclear., Methods: We report two cases of brainstem-isolated TAN (bi-TAN). Moreover, we performed a systematic review of the literature on bi-TAN and extracted data concerning demographics, clinical characteristics, radiological features, and management. The systematic literature search followed PRISMA guidelines and a pre-defined protocol., Results: Eleven patients, including our two, were identified (mean age: 41.3 years, ± 18.8; five males, 45%). Speech disturbance was the most common clinical presentation (45%). The mean latency from Tacrolimus initiation to bi-TAN onset was 26 days (± 30.8). Tacrolimus serum level tested above the reference range in three patients (mean: 26.83 ± 5.48). Brain MRI showed T2-FLAIR hyperintensities; three showed restricted diffusion on ADC maps. Neurological symptoms resolved completely in seven patients (63%) after Tacrolimus withdrawal or dose reduction., Conclusions: Our findings suggest that bi-TAN could represent a brainstem variant of posterior reversible encephalopathy syndrome. Recognition of bi-TAN as a potential cause of isolated brainstem lesions is crucial to disentangle the diagnostic work-up and ensure prompt withdrawal or reduction of the offending agent., (© 2024. Fondazione Società Italiana di Neurologia.)

Because of its involvement in breathing control and neuronal excitability, dysregulation of the serotonin (5-HT) 2C receptor (5-HT2C) might play a key role in sudden unexpected death in epilepsy. Seizure-induced respiratory arrest is thus prevented by a 5-HT2B/C agonist in different seizure model. However, the specific contribution of 5-HT2C in chronic epilepsy-related respiratory dysfunction remains unknown. In a rat model of temporal lobe epilepsy (EPI rats), in which we previously reported interictal respiratory dysfunctions and a reduction of brainstem 5-HT tone, quantitative reverse transcriptase polymerase chain reaction showed overexpression of TPH2 (5-HT synthesis enzyme), SERT (5-HT reuptake transporter), and 5-HT2C transcript levels in the brainstem of EPI rats, and of RNA-specific adenosine deaminase (ADAR1, ADAR2) involved in the production of 5-HT2C isoforms. Interictal ventilation was assessed with whole-body plethysmography before and 2 h after administration of SB242084 (2 mg/kg), a specific antagonist of 5-HT2C. As expected, SB242084 administration induced a progressive decrease in ventilatory parameters and an alteration of breathing stability in both control and EPI rats. However, the size of the SB242084 effect was lower in EPI rats than in controls. Increased 5-HT2C gene expression in the brainstem of EPI rats could be part of a compensatory mechanism against epilepsy-related low 5-HT tone and expression of 5-HT2C isoforms for which 5-HT affinity might be lower., (© 2024 International League Against Epilepsy.)

µ-Opioid receptors (MORs) are responsible for mediating both the analgesic and respiratory effects of opioid drugs. By binding to MORs in brainstem regions involved in controlling breathing, opioids produce respiratory depressive effects characterized by slow and shallow breathing, with potential cardiorespiratory arrest and death during overdose. To better understand the mechanisms underlying opioid-induced respiratory depression, thorough knowledge of the regions and cellular subpopulations that may be vulnerable to modulation by opioid drugs is needed. Using in situ hybridization, we determined the distribution and coexpression of Oprm1 (gene encoding MORs) mRNA with glutamatergic ( Vglut2 ) and neurokinin-1 receptor ( Tacr1 ) mRNA in medullary and pontine regions involved in breathing control and modulation. We found that >50% of cells expressed Oprm1 mRNA in the preBötzinger complex (preBötC), nucleus tractus solitarius (NTS), nucleus ambiguus (NA), postinspiratory complex (PiCo), locus coeruleus (LC), Kölliker-Fuse nucleus (KF), and the lateral and medial parabrachial nuclei (LBPN and MPBN, respectively). Among Tacr1 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, Bötzinger complex (BötC), PiCo, LC, raphe magnus nucleus, KF, LPBN, and MPBN, whereas among Vglut2 mRNA-expressing cells, >50% coexpressed Oprm1 mRNA in the preBötC, NTS, NA, BötC, PiCo, LC, KF, LPBN, and MPBN. Taken together, our study provides a comprehensive map of the distribution and coexpression of Oprm1 , Tacr1 , and Vglut2 mRNA in brainstem regions that control and modulate breathing and identifies Tacr1 and Vglut2 mRNA-expressing cells as subpopulations with potential vulnerability to modulation by opioid drugs. NEW & NOTEWORTHY Opioid drugs can cause serious respiratory side-effects by binding to µ-opioid receptors (MORs) in brainstem regions that control breathing. To better understand the regions and their cellular subpopulations that may be vulnerable to modulation by opioids, we provide a comprehensive map of Oprm1 (gene encoding MORs) mRNA expression throughout brainstem regions that control and modulate breathing. Notably, we identify glutamatergic and neurokinin-1 receptor-expressing cells as potentially vulnerable to modulation by opioid drugs and worthy of further investigation using targeted approaches.

Nutritional status during critical windows in early development can challenge metabolic functions and physiological responses to immune stress in adulthood, such as the systemic inflammation induced by lipopolysaccharide (LPS). The aim of this study was to investigate the long-term effects of post-natal over- and undernutrition on the anorexigenic effect of LPS and its association with neuronal activation in the brainstem and hypothalamus of male rats. Animals were raised in litters of 3 (small - SL), 10 (normal - NL), or 16 (large - LL) pups per dam. On post-natal day 60, male rats were treated with LPS (500 µg/Kg) or vehicle for the evaluation of food intake and c-Fos expression in the area postrema (AP), nucleus of solitary tract (NTS), and paraventricular (PVN), arcuate (ARC), ventromedial (VMH), and dorsomedial (DMH) nuclei of the hypothalamus. SL, NL, and LL animals showed a decreased food consumption after LPS treatment. In under- and normonourished animals, peripheral LPS induced an increase in neuronal activation in the brainstem, PaV, PaMP, and ARC and a decrease in the number of c-Fos-ir neurons in the DMH. Overnourished rats showed a reduced hypophagic response, lower neuron activation in the NTS and PaMP, and no response in the DMH induced by LPS. These results indicate that early nutritional programming displays different responses to LPS, by means of neonatal overnutrition decreasing LPS-mediated anorexigenic effect and neuronal activation in the NTS and hypothalamic nuclei.

The N-methyl-D-aspartate (NMDA) receptor is a glutamate-activated cation channel that is critical to many processes in the brain. Genome-wide association studies suggest that glutamatergic neurotransmission and NMDA receptor-mediated synaptic plasticity are important for body weight homeostasis 1 . Here we report the engineering and preclinical development of a bimodal molecule that integrates NMDA receptor antagonism with glucagon-like peptide-1 (GLP-1) receptor agonism to effectively reverse obesity, hyperglycaemia and dyslipidaemia in rodent models of metabolic disease. GLP-1-directed delivery of the NMDA receptor antagonist MK-801 affects neuroplasticity in the hypothalamus and brainstem. Importantly, targeting of MK-801 to GLP-1 receptor-expressing brain regions circumvents adverse physiological and behavioural effects associated with MK-801 monotherapy. In summary, our approach demonstrates the feasibility of using peptide-mediated targeting to achieve cell-specific ionotropic receptor modulation and highlights the therapeutic potential of unimolecular mixed GLP-1 receptor agonism and NMDA receptor antagonism for safe and effective obesity treatment., (© 2024. The Author(s).)

Linalool and linalyl acetate are major components of lavender essential oil. These substances possess many biological activities, such as anti-inflammatory activity, analgesic and anxiolytic effects, and anticonvulsant properties, and they also induce modulation of neuronal activity in the autonomic nervous system. However, there are no reports of the direct effects of linalool on respiratory activity. In the present study, we analyzed the effects of linalool and linalyl acetate on central respiratory activity in the brainstem-spinal cord preparation isolated from newborn rats. Linalool dose-dependently decreased the rate of respiratory activity. This effect was reversed by bicuculline, suggesting that linalool enhanced inhibitory synaptic connections via GABAA receptors. In addition, linalool reduced the coefficient of variation of inspiratory burst intervals and thus could work to stabilize the respiratory rhythm. Linalyl acetate did not cause inhibitory effects as observed in linalool treatment. Linalool depressed burst activity of pre-inspiratory neurons in the medullary respiratory networks and increased the amplitude of inspiratory inhibitory postsynaptic potentials of pre-inspiratory neurons. We concluded that linalool caused inhibitory effects on respiratory rhythm generation mainly through activation of presynaptic GABAA receptors of pre-inspiratory neurons.

Infections induce a set of pleiotropic responses in animals, including anorexia, adipsia, lethargy and changes in temperature, collectively termed sickness behaviours 1 . Although these responses have been shown to be adaptive, the underlying neural mechanisms have not been elucidated 2-4 . Here we use of a set of unbiased methodologies to show that a specific subpopulation of neurons in the brainstem can control the diverse responses to a bacterial endotoxin (lipopolysaccharide (LPS)) that potently induces sickness behaviour. Whole-brain activity mapping revealed that subsets of neurons in the nucleus of the solitary tract (NTS) and the area postrema (AP) acutely express FOS after LPS treatment, and we found that subsequent reactivation of these specific neurons in FOS 2A-iCreERT2 (also known as TRAP2) mice replicates the behavioural and thermal component of sickness. In addition, inhibition of LPS-activated neurons diminished all of the behavioural responses to LPS. Single-nucleus RNA sequencing of the NTS-AP was used to identify LPS-activated neural populations, and we found that activation of ADCYAP1 + neurons in the NTS-AP fully recapitulates the responses elicited by LPS. Furthermore, inhibition of these neurons significantly diminished the anorexia, adipsia and locomotor cessation seen after LPS injection. Together these studies map the pleiotropic effects of LPS to a neural population that is both necessary and sufficient for canonical elements of the sickness response, thus establishing a critical link between the brain and the response to infection., (© 2022. The Author(s).)

Degenerate neural circuits exhibit "different" circuit properties yet produce similar circuit outcomes (many-to-one) which ensures circuit robustness and complexity. However, neuropathies may hijack degeneracy to yield robust and complex pathological circuits. The aim of the current study was to test the hypothesis that physiochemical exposure to combined jet fuel and noise might induce degeneracy in the brainstem. The auditory brainstem of pigmented rats was used as a model system. The animals were randomized into the following experimental groups: Fuel+Noise, fuel-only, noise-only, and control. Ascending volume conductance from various auditory brainstem regions were evaluated simultaneously with peripheral nervous system (PNS) input to brainstem circuitry. Data demonstrated normal PNS inputs for all groups. However, the Fuel+Noise exposure group produced different caudal brainstem circuit properties while rostral brainstem circuitry initiated outputs that were similar to that of control. This degenerative effect was specific to Fuel+Noise exposure, since neither noise-alone or fuel-alone produced the same result. Degeneracy in the auditory brainstem is consistent with perceptual abnormalities, such as poor speech discrimination (hear but not understand), tinnitus (ringing in the ear), hyperacusis (hypersensitivity to even low-level sound), and loudness intolerance. Therefore, a potential consequence of Fuel+Noise exposure among military and civilian populations may be evidenced as increased rates of super-threshold auditory perceptual abnormalities. This is particularly important because to date, the ototoxic profile of Fuel+Noise exposure has remained unresolved.

Background: Neurosteroids are involved in several important brain functions and have recently been considered novel players in the mechanic actions of neuropsychiatric drugs. There are no reports of murine studies focusing on the effect of chronic neurosteroid treatment in parallel with antipsychotics on key steroidogenic enzyme expression and we therefore focused on steroidogenic enzyme gene expression in the brainstem of rats chronically treated with olanzapine and haloperidol., Methods and Results: Studies were carried out on adult, male Sprague-Dawley rats which were divided into 3 groups: control and experimental animals treated with olanzapine or haloperidol. Total mRNA was isolated from homogenized brainstem samples for RealTime-PCR to estimate gene expression of related aromatase, 3β-HSD and P450scc. Long-term treatment with the selected antipsychotics was reflected in the modulation of steroidogenic enzyme gene expression in the examined brainstem region; with both olanzapine and haloperidol increasing aromatase, 3β-HSD and P450scc gene expression., Conclusions: The present findings shed new light on the pharmacology of antipsychotics and suggest the existence of possible regulatory interplay between neuroleptic action and steroidogenesis at the level of brainstem neuronal centres., (© 2021. The Author(s).)

Pain perception is decreased by shifting attentional focus away from a threatening event. This attentional analgesia engages parallel descending control pathways from anterior cingulate (ACC) to locus coeruleus, and ACC to periaqueductal grey (PAG) - rostral ventromedial medulla (RVM), indicating possible roles for noradrenergic or opioidergic neuromodulators. To determine which pathway modulates nociceptive activity in humans, we used simultaneous whole brain-spinal cord pharmacological-fMRI (N = 39) across three sessions. Noxious thermal forearm stimulation generated somatotopic-activation of dorsal horn (DH) whose activity correlated with pain report and mirrored attentional pain modulation. Activity in an adjacent cluster reported the interaction between task and noxious stimulus. Effective connectivity analysis revealed that ACC interacts with PAG and RVM to modulate spinal cord activity. Blocking endogenous opioids with Naltrexone impairs attentional analgesia and disrupts RVM-spinal and ACC-PAG connectivity. Noradrenergic augmentation with Reboxetine did not alter attentional analgesia. Cognitive pain modulation involves opioidergic ACC-PAG-RVM descending control which suppresses spinal nociceptive activity., Competing Interests: VO, RH, RM, AP, JB No competing interests declared, (© 2022, Oliva et al.)

Fipronil (FIP) is a highly effective insecticide that has been used in agriculture and veterinary medicine. Its neurotoxic effect to insects and to non-target organisms, after nonintentional exposure, was reported. Many studies were conducted to evaluate FIP effects on mammals. However, slight is known about its effect on the brain stem and diencephalon. The current study was designed to investigate the ability of FIP to induce oxidative stress as a molecular mechanism of FIP neurotoxicity that resulted in apoptosis and neural tissue reactivity in these regions. Ten adult male rats received 10 mg/kg of FIP technical grade by oral gavage, daily for 45 days. Brain stem and diencephalon were processed to examine oxidative stress-induced macromolecular alteration (MDA, PCC and DNA fragmentation). Also, the histopathological assessment and immunoreactivity for caspase-3 (active form), iNOS and GFAP were performed on the thalamus, hypothalamus and medulla oblongata. Our results revealed that FIP significantly raised MDA, PCC and DNA fragmentation (p ≤ 0.05). In addition, significantly increased immunoreactivity to GFAP, iNOS and caspase-3 (active form) in the FIP-treated group was noticed (p ≤ 0.05). Moreover, alterations in the histoarchitecture of the neural tissue of these regions were observed. We conclude that FIP can induce oxidative stress, leading to apoptosis and tissue reaction in brain stem and diencephalon., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Neuroplasticity is a fundamental property of the respiratory control system, enabling critical adaptations in breathing to meet the challenges, but little is known whether neonates express neuroplasticity similar to adults. We tested the hypothesis that, similar to adults, tyrosine receptor kinase B (TrkB) or adenosine A2a receptor activation in neonates are independently sufficient to elicit respiratory motor facilitation, and that co-induction of TrkB and A2a receptor-dependent plasticity undermines respiratory motor facilitation. TrkB receptor activation with 7,8-dihydroxyflavone (DHF) in neonatal brainstem-spinal cord preparations induced a long-lasting increase in respiratory motor output in 55 % of preparations, whereas adenosine A2a receptor activation with CGS21680 only sporadically induced respiratory motor plasticity. CGS21680 and DHF co-application prevented DHF-dependent respiratory motor facilitation, whereas co-application of MSX-3 (adenosine A2a receptor antagonist) and DHF more rapidly induced respiratory motor plasticity. Collectively, these data suggest that mechanisms underlying respiratory neuroplasticity may be only partially operational in early neonatal life, and that adenosine A2a receptor activation undermines TrkB-induced respiratory plasticity., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Objective: Complex regional pain syndrome (CRPS) is caused by injuries from fracture after trauma and orthopaedic surgical procedures in the hind limbs. The symptoms of CRPS include warmth, pain, allodynia, and hyperalgesia. It is known that 5-hydroxytryptamine 3 (5-HT3) receptors contribute to hyperalgesia, but their role has not yet been fully elucidated. This study investigated the mechanism of pain relief when a 5-HT3 receptor antagonist was administered in a CRPS animal model., Materials and Methods: To establish a CRPS animal model, 10-week-old Sprague-Dawley rats were used in the experiment. On the fourth week post tibial fracture surgery, we performed the von Frey test to measure mechanical allodynia. After performing behavioural tests, we collected blood and tissue samples after sacrificing the animals. Enzyme-linked immunosorbent assay and western blot were also performed., Results: The experimental tibia fracture model-induced CRPS animals elicited increased 5-HT3 receptor expression, and the 5-HT transporter was decreased in the brain stem after 4 weeks of surgical intervention. Additionally, in CRPS-induced animals, both the concentration of substance P and the level of interleukin 6 were increased peripherally and centrally. Treatment with the 5-HT3 receptor antagonist, ramosetron, exerted an analgesic effect in the paw withdrawal test and was dependent on the attenuation of the 5-HT3 receptor population with inflammatory pain mediators., Conclusions: These data suggest that treatment with the 5-HT3 receptor antagonist, ramosetron, in experimental CRPS animal models alleviated pain-related behaviours and may be a new therapeutic option or potential therapeutic agent for patients with CRPS.

Effects of acetylcholine (ACh) on respiratory activity have been an intriguing theme especially in relation to central chemoreception and the control of hypoglossal nerve activity. We studied the effects of ACh on hypoglossal and phrenic (C4) nerve activities and inspiratory and pre-inspiratory neurons in the rostral ventrolateral medulla in brainstem-spinal cord preparations from newborn rats. ACh application increased respiratory rhythm, decreased inspiratory hypoglossal and C4 nerve burst amplitude, and enhanced pre-inspiratory hypoglossal activity. ACh induced membrane depolarization of pre-inspiratory neurons that might be involved in facilitation of respiratory rhythm by ACh. Effects of ACh on hypoglossal and C4 nerve activity were partially reversed by a nicotinic receptor blocker, mecamylamine. Further application of a muscarinic receptor antagonist, oxybutynin, resulted in slight increase of hypoglossal (but not C4) burst amplitude. Thus, ACh induced different effects on hypoglossal and C4 nerve activity in the brainstem-spinal cord preparation., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Pitt-Hopkins syndrome (PTHS) is a rare autism spectrum-like disorder characterized by intellectual disability, developmental delays, and breathing problems involving episodes of hyperventilation followed by apnea. PTHS is caused by functional haploinsufficiency of the gene encoding transcription factor 4 (Tcf4). Despite the severity of this disease, mechanisms contributing to PTHS behavioral abnormalities are not well understood. Here, we show that a Tcf4 truncation (Tcf4 tr/+ ) mouse model of PTHS exhibits breathing problems similar to PTHS patients. This behavioral deficit is associated with selective loss of putative expiratory parafacial neurons and compromised function of neurons in the retrotrapezoid nucleus that regulate breathing in response to tissue CO 2 /H + . We also show that central Nav1.8 channels can be targeted pharmacologically to improve respiratory function at the cellular and behavioral levels in Tcf4 tr/+ mice, thus establishing Nav1.8 as a high priority target with therapeutic potential in PTHS., (© 2021. The Author(s).)

General anesthetic agents are thought to induce loss-of-consciousness (LOC) and enable pain-free surgery by acting on the endogenous brain circuitry responsible for sleep-wake cycling. In clinical use, the entire CNS is exposed to anesthetic molecules with LOC and amnesia usually attributed to synaptic suppression in the cerebral cortex and immobility and analgesia to agent action in the spinal cord and brainstem. This model of patch-wise suppression has been challenged, however, by the observation that all functional components of anesthesia can be induced by focal delivery of minute quantities of GABAergic agonists to the brainstem mesopontine tegmental anesthesia area (MPTA). We compared spectral features of the cortical electroencephalogram (EEG) in rats during systemic anesthesia and anesthesia induced by MPTA microinjection. Systemic administration of (GABAergic) pentobarbital yielded the sustained, δ-band dominant EEG signature familiar in clinical anesthesia. In contrast, anesthesia induced by MPTA microinjection (pentobarbital or muscimol) featured epochs of δ-band EEG alternating with the wake-like EEG, the pattern typical of natural non-rapid-eye-movement (NREM) and REM sleep. The rats were not sleeping, however, as they remained immobile, atonic and unresponsive to noxious pinch. Recalling the paradoxical wake-like quality the EEG during REM sleep, we refer to this state as "paradoxical anesthesia". GABAergic anesthetics appear to co-opt both cortical and spinal components of the sleep network via dedicated axonal pathways driven by MPTA neurons. Direct drug exposure of cortical and spinal neurons is not necessary, and is probably responsible for off-target side-effects of systemic administration including monotonous δ-band EEG, hypothermia and respiratory depression. SIGNIFICANCE STATEMENT: The concept that GABAergic general anesthetic agents induce loss-of-consciousness by substituting for an endogenous neurotransmitter, thereby co-opting neural circuitry responsible for sleep-wake transitions, has gained considerable traction. However, the electroencephalographic (EEG) signatures of sleep and anesthesia differ fundamentally. We show that when the anesthetic state is generated by focal delivery of GABAergics into the mesopontine tegmental anesthesia area (MPTA) the resulting EEG repeatedly transitions between delta-wave-dominant and wake-like patterns much as in REM-NREM sleep. This suggests that systemic (clinical) anesthetic delivery, which indiscriminately floods the entire cerebrum with powerful inhibitory agents, obscures the sleep-like EEG signature associated with the less adulterated form of anesthesia obtained when the drugs are applied selectively to loci where the effective neurotransmitter substitution actually occurs., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Using drugs of abuse while pregnant has tremendous negative consequences for the offspring, including an enhanced risk for substance use disorder (SUD). This vulnerability suggests that gestational exposure to drugs alters the developmental trajectory of neurons important in SUD processes, which could lead to later life changes in responsiveness to motivationally salient stimuli. The laterodorsal tegmentum (LDT) gates the behaviorally relevant firing pattern signaling stimuli saliency in mesoaccumbal circuits. Accordingly, any alterations in LDT functionality could alter output, and play a role in negative outcomes on motivated behavior associated with early-life nicotine exposure. Therefore, we investigated whether prenatal exposure to nicotine (PNE), which is a known teratogen, altered responsiveness of LDT neurons to alcohol by conducting electrophysiology in brain slices. Alcohol induced an outward current in control LDT cells, which was not seen in PNE LDT neurons. The frequency of mEPSCs was significantly decreased by alcohol in LDT PNE cells and accompanied by a decrease in action potential frequency, which were actions not seen in controls. Changes in baseline activity of PNE LDT cells were also observed. In summary, PNE LDT neurons showed alterations in baseline activity and membrane and synaptic responses to postnatal exposures to alcohol. The differences in PNE baseline activity and alcohol responses likely lead to differential output from the LDT to mesoaccumbal targets that could play a role in biasing coding of relevant stimuli, which could participate in the enhanced proclivity for development of SUD in those exposed during gestation to nicotine., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Phoenixin, spexin and nesfatin-1 belong to a family of newly discovered multifunctional neuropeptides that play regulatory roles in several brain structures and modulate the activity of important neural networks. However, little is known about their expression and action at the level of brainstem. The present work was, therefore, focused on gene expression of the aforementioned peptides in the brainstem of rats chronically treated with olanzapine, a second generation antipsychotic drug., Methods: Studies were carried out on adult, male Sprague-Dawley rats that were divided into 2 groups: control and experimental animals treated with olanzapine (28-day-long intraperitoneal injection, at dose 5 mg/kg daily). All individuals were killed under anesthesia and the brainstem excised. Total mRNA was isolated from homogenized samples of both structures and the RT-PCR method was used for estimation of related SMIM20/phoenixin, NPQ/spexin and NUCB2/nesfatin-1 gene expression., Results: Long-term treatment with olanzapine is reflected in qualitatively different changes in expression of examined neuropeptides mRNA in the rat brainstem. Olanzapine significantly decreased NPQ/spexin mRNA expression, but increased SMIM20/phoenixin mRNA level in the rat brainstem; while NUCB2/nesfatin-1 mRNA expression remained unchanged., Conclusions: Olanzapine can affect novel peptidergic signaling in the rat brainstem. This may cautiously suggest the presence of an alternative mode of its action., (© 2021. The Author(s).)

Clinical research into consciousness has long focused on cortical macroscopic networks and their disruption in pathological or pharmacological consciousness perturbation. Despite demonstrating diagnostic utility in disorders of consciousness (DoC) and monitoring anesthetic depth, these cortico-centric approaches have been unable to characterize which neurochemical systems may underpin consciousness alterations. Instead, preclinical experiments have long implicated the dopaminergic ventral tegmental area (VTA) in the brainstem. Despite dopaminergic agonist efficacy in DoC patients equally pointing to dopamine, the VTA has not been studied in human perturbed consciousness. To bridge this translational gap between preclinical subcortical and clinical cortico-centric perspectives, we assessed functional connectivity changes of a histologically characterized VTA using functional MRI recordings of pharmacologically (propofol sedation) and pathologically perturbed consciousness (DoC patients). Both cohorts demonstrated VTA disconnection from the precuneus and posterior cingulate (PCu/PCC), a main default mode network node widely implicated in consciousness. Strikingly, the stronger VTA-PCu/PCC connectivity was, the more the PCu/PCC functional connectome resembled its awake configuration, suggesting a possible neuromodulatory relationship. VTA-PCu/PCC connectivity increased toward healthy control levels only in DoC patients who behaviorally improved at follow-up assessment. To test whether VTA-PCu/PCC connectivity can be affected by a dopaminergic agonist, we demonstrated in a separate set of traumatic brain injury patients without DoC that methylphenidate significantly increased this connectivity. Together, our results characterize an in vivo dopaminergic connectivity deficit common to reversible and chronic consciousness perturbation. This noninvasive assessment of the dopaminergic system bridges preclinical and clinical work, associating dopaminergic VTA function with macroscopic network alterations, thereby elucidating a critical aspect of brainstem-cortical interplay for consciousness., Competing Interests: The authors declare no competing interest.

Cranial parasympathetic activation produces vasodilation in the head and neck region, but little is known about its central and peripheral mechanisms. This study was conducted to examine whether external and internal carotid-vasodilation origin sites triggered by chemical stimulation are distributed topographically in the parasympathetic brainstems of anesthetized rats, and to examine the effects of peripheral receptors on vasodilation. Microinjection of the neuromodulator candidate l-cysteine revealed that external and internal carotid vasodilation-triggering sites were distributed non-topographically along the full extent of the parasympathetic parvocellular reticular formation (PcRt). Intravenous injection of a muscarinic blocker and a nitric oxide synthase inhibitor abolished external carotid vasodilation, suggesting the peripheral involvement of muscarinic and nitric oxide receptors. Further work is needed to fully understand the PcRt mechanisms underlying timely and appropriate vasodilation to support various cranial functions., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Akt (protein kinase B) signaling is frequently activated in diverse cancers. Akt inhibitors such as perifosine and MK-2206 have been evaluated as potential cancer chemotherapeutics. Although both drugs are generally well tolerated, among their most common side-effects vomiting is a major concern. Here we investigated whether these Akt inhibitors evoke emesis in the least shrew model of vomiting. Indeed, both perifosine and MK-2206 induced vomiting with maximal efficacies of 90% at 50 mg/kg (i.p.) and 100% at 10 mg/kg (i.p.), respectively. MK-2206 (10 mg/kg, i.p.) increased c-Fos immunoreactivity both centrally in the shrew brainstem dorsal vagal complex (DVC) emetic nuclei, and peripherally in the jejunum. MK-2206 also evoked phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in both the DVC emetic nuclei and the enteric nervous system in the jejunum. The ERK1/2 inhibitor U0126 suppressed MK-2206-induced emesis dose-dependently. We then evaluated the suppressive efficacy of diverse antiemetics against MK-2206-evoked vomiting including antagonists/inhibitors of the: L-type Ca 2+ channel (nifedipine at 2.5 mg/kg, subcutaneously (s.c.)); glycogen synthase kinase 3 (GSK-3) (AR-A014418 at 10 mg/kg and SB216763 at 0.25 mg/kg, i.p.); 5-hydroxytryptamine 5-HT 3 receptor (palonosetron at 0.5 mg/kg, s.c.); substance P neurokinin NK 1 receptor (netupitant at 10 mg/kg, i.p.) and dopamine D 2/3 receptor (sulpride at 8 mg/kg, s.c.). All tested antagonists/blockers attenuated emetic parameters to varying degrees. In sum, this is the first study to demonstrate how pharmacological inhibition of Akt evokes vomiting via both central and peripheral mechanisms, a process which involves multiple emetic receptors., (Copyright © 2021 The Author(s). Published by Elsevier B.V. All rights reserved.)

Abstract: Inconsistent reports are available on the role of testosterone in end-organ damage caused by endotoxemia. Here, pharmacologic, surgical, and molecular studies were employed to assess the testosterone modulation of cardiovascular, autonomic, and peripheral and central inflammatory derangements caused by endotoxemia. Studies were performed in conscious male rats preinstrumented with femoral indwelling catheters for the measurement of blood pressure and subjected to castration or pharmacologic interventions that interrupt the biosynthetic cascade of testosterone. Compared with the effects of lipopolysaccharide (10 mg/kg intravenously) in sham operated rats, 2-week castration reduced the lipopolysaccharide-evoked (1) falls in blood pressure, (2) decreases in time- and frequency-domain indices of heart rate variability, (3) shifts in spectral measures of cardiac sympathovagal balance toward parasympathetic dominance, and (4) increases in protein expressions of toll-like receptor-4 and monocyte chemoattractant protein-1 in heart and medullary neurons of the nucleus tractus solitarius and rostral ventrolateral medulla. While the ameliorating actions of castration on endotoxic cardiovascular manifestations were maintained after testosterone replacement, the concomitant inflammatory signals were restored to near-sham levels. The favorable influences of castration on inflammatory and cardiovascular abnormalities of endotoxemia were replicated in intact rats pretreated with degarelix (gonadotropin-releasing hormone receptor blocker) or finasteride (5α-reductase inhibitor) but not formestane (aromatase inhibitor). The data signifies the importance of androgens and its biosynthetic enzymes in cardiovascular and autonomic insults induced by the endotoxic inflammatory response. Clinically, the interruption of testosterone biosynthesis could offer a potential strategy for endotoxemia management., Competing Interests: The authors report no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

A neural circuit between the paraventricular nucleus of the hypothalamus (PVN) and the dorsal motor nucleus of the vagus (DMNV) constitutes part of an important parasympathetic autonomic pathway that controls hepatic glucose production. Intracerebroventricular injection of insulin activates oxytocinergic neurones in the PVN and elicits the release of oxytocin into the circulation, which plays an important role in the metabolism of glucose. Moreover, the central action of insulin can reduce the concentration of glucose in blood taken from the hepatic vein of Wistar rats via activation of vagal efferent nerves to the liver. This mechanism is impaired in sedentary spontaneously hypertensive rats (SHR). Because aerobic exercise increases vagal tone, partly mediated by increasing the oxytocinergic connections between the PVN and DMNV, we hypothesised that oxytocin (OT) might alter the excitability of liver-projecting DMNV neurones. Thus, we investigated the effects of OT on electrical properties of the liver-projecting DMNV neurones from Wistar, SHR subjected to 4 weeks of exercise training, as well sedentary controls, using whole cell patch-clamping. The results show that OT increased the resting membrane potential of DMNV neurones in Wistar rats, as well as the firing frequency of these cells, but not in sedentary SHR. However, in SHR subjected to 4 weeks of exercise training, the effects of OT on liver-projecting DMNV neurones of were similar to those seen in Wistar rats. These findings show that OT elicits similar changes in the electrophysiological properties of liver-projecting DMNV neurones of Wistar and exercise-trained but not sedentary SHR. These results indicate that exercise training can restore the sensitivity of liver-projecting DMNV neurones of exercise-trained SHR to OT., (© 2021 British Society for Neuroendocrinology.)

Methyl palmitate (MP) is a fatty acid methyl ester. Our recent study indicated that adrenergic nerve-dependent functional sympathetic-sensory nerve interactions were abolished by MP in mesenteric arteries. However, the effect of MP on perivascular nerves and cerebral blood flow remains unclear. In this study, the increase in basilar arterial blood flow (BABF) after the topical application of nicotinic acetylcholine receptor agonists was measured using laser Doppler flowmetry in anesthetized rats. The choline (a selective α7-nicotinic acetylcholine receptor agonist)-induced increase in BABF was abolished by tetrodotoxin (a neurotoxin), N G -nitro-L-arginine (a nonselective NO synthase inhibitor), α-bungarotoxin (a selective α7-nicotinic acetylcholine receptor inhibitor), and chronic sympathetic denervation. In addition, the nicotine (a nicotinic acetylcholine receptor agonist)-induced increase in BABF was inhibited by MP in a concentration-dependent manner. The acetylcholine-induced increase in BABF was not affected by MP. The myography results revealed that nicotine-induced vasorelaxation was significantly inhibited by MP, but was reversed by chelerythrine (a protein kinase C inhibitor). MP-induced vasodilation was significantly greater in BA rings without endothelium compared to those with endothelium. Meanwhile, MP did not affect baseline BABF. Our results indicate that MP acts as a neuromodulator in the cerebral circulation where it activates the PKC pathway and causes a diminished nicotine-induced increase in blood flow in the brainstem, and that the vasorelaxation effect of MP may play a minor role., (© 2021 John Wiley & Sons Ltd.)

Many general anesthetics potentiate gamma-aminobutyric acid (GABA) A receptors but their neuroanatomic sites of action are less clear. GABAergic neurons in the rostromedial tegmental nucleus (RMTg) send inhibitory projections to multiple arousal-promoting nuclei, but the role of these neurons in modulating consciousness is unknown. In this study, designer receptors exclusively activated by designer drugs (DREADDs) were targeted to RMTg GABAergic neurons of Vgat-ires-Cre mice. DREADDs expression was found in the RMTg and other brainstem regions. Activation of these neurons decreased movement and exploratory behavior, impaired motor coordination, induced electroencephalogram (EEG) oscillations resembling nonrapid eye movement (NREM) sleep without loss of righting and reduced the dose requirement for sevoflurane-induced unconsciousness. These results suggest that GABAergic neurons in the RMTg and other brainstem regions promote sedation and facilitate sevoflurane-induced unconsciousness., Competing Interests: Conflicts of Interest: See Disclosures at the end of the article., (Copyright © 2021 International Anesthesia Research Society.)

The neural network that regulates breathing shows a significant sexual dimorphism. Ovarian hormones contribute to this distinction as, in rats, ovariectomy reduces the ventilatory response to CO 2 . Microglia are neuroimmune cells that are sensitive to neuroendocrine changes in their environment. When reacting to challenging conditions, these cells show changes in their morphology that reflect an augmented capacity for producing pro- and anti-inflammatory cytokines. Based on evidence suggesting that microglia contribute to sex-based differences in reflexive responses to hypercapnia, we hypothesized that ovariectomy and hypercapnia promote microglial reactivity in selected brain areas that regulate breathing. We used ionized calcium-binding-adapter molecule-1 (Iba1) immunolabeling to compare the density and morphology of microglia in the locus coeruleus (LC), the caudal medullary raphe, the caudal part of the nucleus of the tractus solitarius (cNTS), and the paraventricular nucleus of the hypothalamus (PVN). Tissue was obtained from SHAM (metaestrus) female rats or following ovariectomy. Rats were exposed to normocapnia or hypercapnia (5% CO 2, 20 min). Ovariectomy and hypercapnia did not affect microglial density in any of the structures studied. Ovariectomy promoted a reactive phenotype in the cNTS and LC, as indicated by a larger morphological index. In these structures, hypercapnia had a relatively modest opposing effect; the medullary raphe or the PVN were not affected. We conclude that ovarian hormones attenuate microglial reactivity in CO 2 /H + sensing structures. These data suggest that microglia may contribute to neurological diseases in which anomalies of respiratory control are associated with cyclic fluctuations of ovarian hormones or menopause., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Drug delivery in diffuse intrinsic pontine glioma is significantly limited by the blood-brain barrier (BBB). Focused ultrasound (FUS), when combined with the administration of microbubbles can effectively open the BBB permitting the entry of drugs across the cerebrovasculature into the brainstem. Given that the utility of FUS in brainstem malignancies remains unknown, the purpose of our study was to determine the safety and feasibility of this technique in a murine pontine glioma model. A syngeneic orthotopic model was developed by stereotactic injection of PDGF-B + PTEN -/- p53 -/- murine glioma cells into the pons of B6 mice. A single-element, spherical-segment 1.5 MHz ultrasound transducer driven by a function generator through a power amplifier was used with concurrent intravenous microbubble injection for tumor sonication. Mice were randomly assigned to control, FUS and double-FUS groups. Pulse and respiratory rates were continuously monitored during treatment. BBB opening was confirmed with gadolinium-enhanced MRI and Evans blue. Kondziela inverted screen testing and sequential weight lifting measured motor function before and after sonication. A subset of animals were treated with etoposide following ultrasound. Mice were either sacrificed for tissue analysis or serially monitored for survival with daily weights. FUS successfully caused BBB opening while preserving normal cardiorespiratory and motor function. Furthermore, the degree of intra-tumoral hemorrhage and inflammation on H&E in control and treated mice was similar. There was also no difference in weight loss and survival between the groups (p > 0.05). Lastly, FUS increased intra-tumoral etoposide concentration by more than fivefold. FUS is a safe and feasible technique for repeated BBB opening and etoposide delivery in a preclinical pontine glioma model.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by selective neuronal death in the brain stem and spinal cord. The cause is unknown, but an increasing amount of evidence has firmly certified that neuroinflammation plays a key role in ALS pathogenesis. Neuroinflammation is a pathological hallmark of several neurodegenerative disorders and has been implicated as driver of disease progression. Here, we describe a treatment study demonstrating the therapeutic potential of a tandem version of the well-known all-d-peptide RD2 (RD2RD2) in a transgenic mouse model of ALS (SOD1*G93A). Mice were treated intraperitoneally for four weeks with RD2RD2 vs. placebo. SOD1*G93A mice were tested longitudinally during treatment in various behavioural and motor coordination tests. Brain and spinal cord samples were investigated immunohistochemically for gliosis and neurodegeneration. RD2RD2 treatment in SOD1*G93A mice resulted not only in a reduction of activated astrocytes and microglia in both the brain stem and lumbar spinal cord, but also in a rescue of neurons in the motor cortex. RD2RD2 treatment was able to slow progression of the disease phenotype, especially the motor deficits, to an extent that during the four weeks treatment duration, no significant progression was observed in any of the motor experiments. Based on the presented results, we conclude that RD2RD2 is a potential therapeutic candidate against ALS.

Recent work identified Gpr160 as a candidate receptor for cocaine- and amphetamine-regulated transcript peptide (CARTp) and described its role in pain modulation. The aims of the present study were to determine if Gpr160 is required for the CARTp's ability to reduce food intake and water intake and to initially identify the distribution of Gpr160-like immunoreactivity (Gpr160ir) in the rat brain. A passive immunoneutralization approach targeting Gpr160 was used to block the behavioral effects of a pharmacological dose of CARTp in the fourth cerebroventricle (4V) of rats and to determine the importance of endogenously produced CARTp in the control of ingestive behaviors. Passive immunoneutralization of Gpr160 in the 4V blocked the actions of CARTp to inhibit food intake and water intake. Blockade of Gpr160 in the 4V, independent of pharmacological CART treatment, caused an increase in both overnight food intake and water intake. The decrease in food intake, but not water intake, caused by central injection of CARTp was demonstrated to be interrupted by prior administration of a glucagon-like peptide 1 (GLP-1) receptor antagonist. Gpr160ir was observed in several, distinct sites throughout the rat brain, where CARTp staining has been described. Importantly, Gpr160ir was observed to be present in both neuronal and nonneuronal cell types. These data support the hypothesis that Gpr160 is required for the anorexigenic actions of central CARTp injection and extend these findings to water drinking. Gpr160ir was observed in both neuronal and nonneuronal cell types in regions known to be important in the multiple pharmacological effects of CARTp, identifying those areas as targets for future compromise of function studies.

Recent evidence shows that chronic activation of catecholaminergic neurons of the rostral ventrolateral medulla is crucial in promoting autonomic imbalance and cardiorespiratory dysfunction in high output heart failure (HF). Brainstem endoplasmic reticulum stress (ERS) is known to promote cardiovascular dysfunction; however, no studies have addressed the potential role of brainstem ERS in cardiorespiratory dysfunction in high output HF. In this study, we assessed the presence of brainstem ERS and its potential role in cardiorespiratory dysfunction in an experimental model of HF induced by volume overload. High output HF was surgically induced via creation of an arterio-venous fistula in adult male Sprague-Dawley rats. Tauroursodeoxycholic acid (TUDCA), an inhibitor of ERS, or vehicle was administered intracerebroventricularly for 4 weeks post-HF induction. Compared with vehicle treatment, TUDCA improved cardiac autonomic balance (LF HRV /HF HRV ratio, 3.02±0.29 versus 1.14±0.24), reduced cardiac arrhythmia incidence (141.5±26.7 versus 35.67±12.5 events/h), and reduced abnormal respiratory patterns (Apneas: 11.83±2.26 versus 4.33±1.80 events/h). TUDCA administration (HF+Veh versus HF+TUDCA, P <0.05) attenuated cardiac hypertrophy (HW/BW 4.4±0.3 versus 4.0±0.1 mg/g) and diastolic dysfunction. Analysis of rostral ventrolateral medulla gene expression confirmed the presence of ERS, inflammation, and activation of renin-angiotensin system pathways in high output HF and showed that TUDCA treatment completely abolished ERS and ERS-related signaling. Taken together, these results support the notion that ERS plays a role in cardiorespiratory dysfunction in high output HF and more importantly that reducing brain ERS with TUDCA treatment has a potent salutary effect on cardiac function in this model.

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of mortality in patients with intractable epilepsy. However, the pathogenesis of SUDEP seems to be poorly understood. Our previous findings showed that the incidence of seizure-induced respiratory arrest (S-IRA) was markedly reduced by atomoxetine in a murine SUDEP model. Because the central norepinephrine α-1 receptor (NEα-1R) plays a vital role in regulating respiratory function, we hypothesized that the suppression of S-IRA by atomoxetine was mediated by NE/NEα-1R interactions that can be reversed by NEα-1R antagonism. We examined whether atomoxetine-mediated suppression of S-IRA evoked by either acoustic stimulation or pentylenetetrazole (PTZ) in DBA/1 mice can be reversed by intraperitoneal (IP) and intracerebroventricular (ICV) administration of prazosin, a selective antagonist of NEα-1R. The content and activity of tyrosine hydroxylase (TH), a rate-limiting enzyme for NE synthesis, in the lower brainstem was measured by ELISA. Electroencephalograms (EEG) were obtained from using the PTZ-evoked SUDEP model. In our models, atomoxetine-mediated suppression of S-IRA evoked by either acoustic stimulation or PTZ was significantly reversed by low doses of IP and ICV prazosin. Neither repetitive acoustic stimulation nor S-IRA reduced TH levels in lower brainstem. However, the enzyme activity of TH levels in lower brainstem was significantly increased by mechanical ventilation with DBA/1 mice, which makes the dying DBA/1 mice suffering from S-IRA and SUDEP recover. EEG data showed that although the protective effect of atomoxetine was reversed by prazosin, neither drug suppressed EEG activity. These data suggest that deficient synthesis of NE and norepinephrinergic neurotransmission contributed to S-IRA and that the NEα-1R is a potential therapeutic target for the prevention of SUDEP., (Copyright © 2020 The Author(s). Published by Elsevier Masson SAS.. All rights reserved.)

Early ethanol exposure alters neonatal breathing plasticity. Respiratory EtOH's effects are attributed to central respiratory network disruptions, particularly in the medullary serotonin (5HT) system. In this study we evaluated the effects of neonatal pre-exposure to low/moderate doses upon breathing rates, activation patterns of brainstem's nuclei and expression of 5HT 2A and 2C receptors. At PD9, breathing frequencies, tidal volumes and apneas were examined in pups pre-exposed to vehicle or ethanol (2.0 g/kg) at PDs 3, 5 and 7. This developmental stage is equivalent to the 3 rd human gestational trimester, characterized by increased levels of synaptogenesis. Pups were tested under sobriety or under the state of ethanol intoxication and when subjected to normoxia or hypoxia. Number of c-Fos and 5HT immunolabelled cells and relative mRNA expression of 5HT 2A and 2C receptors were quantified in the brainstem. Under normoxia, ethanol pre-exposed pups exhibited breathing depressions and a high number of apneas. An opposite phenomenon was found in ethanol pre-treated pups tested under hypoxia where an exacerbated hypoxic ventilatory response (HVR) was observed. The breathing depression was associated with an increase in the neural activation levels of the raphe obscurus (ROb) and a high mRNA expression of the 5HT 2A receptor in the brainstem while desactivation of the ROb and high activation levels in the solitary tract nucleus and area postrema were associated to the exacerbated HVR. In summary, early ethanol experience induces respiratory disruptions indicative of sensitization processes. Neuroadaptive changes in central respiratory areas under consideration appear to be strongly associated with changes in their respiratory plasticity., (Copyright © 2020 Elsevier B.V. All rights reserved.)

NADPH diaphorase is used as a histochemical marker of nitric oxide synthase (NOS) in aldehyde-treated tissues. It is thought that the catalytic activity of NOS promotes NADPH-dependent reduction of nitro-blue tetrazolium (NBT) to diformazan. However, it has been argued that a proteinaceous factor other than NOS is responsible for producing diformazan in aldehyde-treated tissues. We propose this is a NO-containing factor such as an S-nitrosothiol and/or a dinitrosyl-iron (II) cysteine complex or nitrosated proteins including NOS. We now report that (1) S-nitrosothiols covalently modify both NBT and TNBT, but only change the reduction potential of NBT after modification, (2) addition of S-nitrosothiols or β- or α-NADPH to solutions of NBT did not elicit diformazan, (3) addition of S-nitrosothiols to solutions of NBT plus β- or α-NADPH elicited rapid formation of diformazan in the absence or presence of paraformaldehyde, (4) addition of S-nitrosothiols to solutions of NBT plus β- or α-NADP did not produce diformazan, (5) S-nitrosothiols did not promote NADPH-dependent reduction of tetra-nitro-blue tetrazolium (TNBT) in which all four phenolic rings are nitrated, (6) cytoplasmic vesicles in vascular endothelial cells known to stain for NADPH diaphorase were rich in S-nitrosothiols, and (7) procedures that accelerate decomposition of S-nitrosothiols, markedly reduced NADPH diaphorase staining in tissue sections subsequently subjected to paraformaldehyde fixation. Our results suggest that NADPH diaphorase in aldehyde-fixed tissues is not enzymatic but is due to the presence of NO-containing factors (free SNOs or nitrosated proteins such as NOS), which promote NADPH-dependent reduction of NBT to diformazan.

Mechanosensitivity is a well-known feature of astrocytes, however, its underlying mechanisms and functional significance remain unclear. There is evidence that astrocytes are acutely sensitive to decreases in cerebral perfusion pressure and may function as intracranial baroreceptors, tuned to monitor brain blood flow. This study investigated the mechanosensory signaling in brainstem astrocytes, as these cells reside alongside the cardiovascular control circuits and mediate increases in blood pressure and heart rate induced by falls in brain perfusion. It was found that mechanical stimulation-evoked Ca 2+ responses in astrocytes of the rat brainstem were blocked by (1) antagonists of connexin channels, connexin 43 (Cx43) blocking peptide Gap26, or Cx43 gene knock-down; (2) antagonists of TRPV4 channels; (3) antagonist of P2Y 1 receptors for ATP; and (4) inhibitors of phospholipase C or IP3 receptors. Proximity ligation assay demonstrated interaction between TRPV4 and Cx43 channels in astrocytes. Dye loading experiments showed that mechanical stimulation increased open probability of carboxyfluorescein-permeable membrane channels. These data suggest that mechanosensory Ca 2+ responses in astrocytes are mediated by interaction between TRPV4 and Cx43 channels, leading to Cx43-mediated release of ATP which propagates/amplifies Ca 2+ signals via P2Y 1 receptors and Ca 2+ recruitment from the intracellular stores. In astrocyte-specific Cx43 knock-out mice the magnitude of heart rate responses to acute increases in intracranial pressure was not affected by Cx43 deficiency. However, these animals displayed lower heart rates at different levels of cerebral perfusion, supporting the hypothesis of connexin hemichannel-mediated release of signaling molecules by astrocytes having an excitatory action on the CNS sympathetic control circuits. SIGNIFICANCE STATEMENT There is evidence suggesting that astrocytes may function as intracranial baroreceptors that play an important role in the control of systemic and cerebral circulation. To function as intracranial baroreceptors, astrocytes must possess a specialized membrane mechanism that makes them exquisitely sensitive to mechanical stimuli. This study shows that opening of connexin 43 (Cx43) hemichannels leading to the release of ATP is the key central event underlying mechanosensory Ca 2+ responses in astrocytes. This astroglial mechanism plays an important role in the autonomic control of heart rate. These data add to the growing body of evidence suggesting that astrocytes function as versatile surveyors of the CNS metabolic milieu, tuned to detect conditions of potential metabolic threat, such as hypoxia, hypercapnia, and reduced perfusion., (Copyright © 2020 Turovsky et al.)

During the last 50 years, the serotonergic (5-HT) system was reported to exert a complex modulation of locomotor activity. Here, we focus on two key factors that likely contribute to such complexity. First, locomotion is modulated directly and indirectly by 5-HT neurons. The locomotor circuitry is directly innervated by 5-HT neurons in the caudal brainstem and spinal cord. Also, indirect control of locomotor activity results from ascending projections of 5-HT cells in the rostral brainstem that innervate multiple brain centers involved in motor action planning. Second, each approach used to manipulate the 5-HT system likely engages different 5-HT-dependent mechanisms. This includes the recruitment of different 5-HT receptors, which can have excitatory or inhibitory effects on cell activity. These receptors can be located far or close to the 5-HT release sites, making their activation dependent on the level of 5-HT released. Here we review the activity of different 5-HT nuclei during locomotor activity, and the locomotor effects of 5-HT precursors, exogenous 5-HT, selective 5-HT reuptake inhibitors (SSRI), electrical or chemical stimulation of 5-HT neurons, genetic deletions, optogenetic and chemogenetic manipulations. We highlight both the coherent and controversial aspects of 5-HT modulation of locomotor activity from basal vertebrates to mammals. This mini review may hopefully inspire future studies aiming at dissecting the complex effects of 5-HT on locomotor function., (Copyright © 2020 Flaive, Fougère, van der Zouwen and Ryczko.)

This study aimed to determine the effects of melatonin on irradiation-induced apoptosis and oxidative stress in the brainstem region of Wistar rats. Therefore, the animals underwent whole-brain X-radiation with a single dose of 25 Gy in the presence or absence of melatonin pretreatment at a concentration of 100 mg/kg BW. The rats were allocated into four groups (10 rats in each group): namely, vehicle control (VC), 100 mg/kg of melatonin alone (MLT), irradiation-only (RAD), and irradiation plus 100 mg/kg of melatonin (RAM). An hour before irradiation, the animals received intraperitoneal (IP) melatonin and then were killed after 6 hr, followed by measurement of nitric oxide (NO), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), and total antioxidant capacity (TAC) in the brainstem region. Furthermore, the western blot analysis technique was performed to assess the caspase-3 expression level. Results showed significantly higher MDA and NO levels in the brainstem tissues for the RAD group when compared with the VC group (p < .001). Moreover, the irradiated rats exhibited a significant decrease in the levels of CAT, SOD, GPx, and TAC (p < .01, p < .001, p < .001, and p < .001, respectively) in comparison to the VC group. The results of apoptosis assessment revealed that the expression level of caspase-3 significantly rose in the RAD group in comparison with the VC group (p < .001). Pretreatment with melatonin ameliorated the radiation-induced adverse effects by decreasing the MDA and NO levels (p < .001) and increasing the antioxidant enzyme activities (p < .001). Consequently, the caspase-3 protein expression level in the RAM group showed a significant reduction in comparison with the RAD group (p < .001). In conclusion, melatonin approximately showed a capacity for neuroprotective activity in managing irradiation-induced oxidative stress and apoptosis in the brainstem of rats; however, the use of melatonin as a neuroprotective agent in humans requires further study, particularly clinical trials., (© 2020 Wiley Periodicals, Inc.)

We recently demonstrated that when mice are exposed to chronic mild hypoxia (CMH, 8% O 2 ), blood vessels in the spinal cord show transient vascular leak that is associated with clustering and activation of microglia around disrupted vessels. Importantly, microglial depletion profoundly increased hypoxia-induced vascular leak, implying that microglia play a critical role maintaining vascular integrity in the hypoxic spinal cord. The goal of the current study was to examine if microglia play a similar vasculo-protective function in the brain. Employing extravascular fibrinogen leak as an index of blood-brain barrier (BBB) disruption, we found that CMH provoked transient vascular leak in cerebral blood vessels that was associated with activation and aggregation of Mac-1-positive microglia around leaky vessels. Interestingly, CMH-induced vascular leak showed regional selectivity, being much more prevalent in the brainstem and olfactory bulb than the cerebral cortex and cerebellum. Pharmacological depletion of microglia with the colony stimulating factor-1 receptor inhibitor PLX5622, had no effect under normoxic conditions, but markedly increased hypoxia-induced cerebrovascular leak in all regions examined. As in the spinal cord, this was associated with endothelial induction of MECA-32, a marker of leaky CNS endothelium, and greater loss of endothelial tight junction proteins. Brain regions displaying the highest levels of hypoxic-induced vascular leak also showed the greatest levels of angiogenic remodeling, suggesting that transient BBB disruption may be an unwanted side-effect of hypoxic-induced angiogenic remodeling. As hypoxia is common to a multitude of human diseases including obstructive sleep apnea, lung disease, and age-related pulmonary, cardiac and cerebrovascular dysfunction, our findings have important translational implications. First, they point to a potential pathogenic role of chronic hypoxia in triggering BBB disruption and subsequent neurological dysfunction, and second, they demonstrate an important protective role for microglia in maintaining vascular integrity in the hypoxic brain.

Aims: Activation of the angiotensin (Ang)-(1-7)/Mas receptor (R) axis protects from sympathetic overactivity. Endocytic trafficking is an essential process that regulates receptor (R) function and its ultimate cellular responses. We investigated whether the blunted responses to Ang-(1-7) in hypertensive rats are associated to an alteration in MasR trafficking., Methods and Results: Brainstem neurons from Wistar-Kyoto (WKY) or spontaneously hypertensive rats (SHRs) were investigated for (i) Ang-(1-7) levels and binding and MasR expression, (ii) Ang-(1-7) responses (arachidonic acid and nitric oxide release and Akt and ERK1/2 phosphorylation), and (iii) MasR trafficking. Ang-(1-7) was determined by radioimmunoassay. MasR expression and functionality were evaluated by western blot and binding assays. MasR trafficking was evaluated by immunofluorescence. Ang-(1-7) treatment induced an increase in nitric oxide and arachidonic acid release and ERK1/2 and Akt phosphorylation in WKY neurons but did not have an effect in SHR neurons. Although SHR neurons showed greater MasR expression, Ang-(1-7)-elicited responses were substantially diminished presumably due to decreased Ang-(1-7) endogenous levels concomitant with impaired binding to its receptor. Through immunocolocalization studies, we evidenced that upon Ang-(1-7) stimulation MasRs were internalized through clathrin-coated pits and caveolae into early endosomes and slowly recycled back to the plasma membrane. However, the fraction of internalized MasRs into early endosomes was larger and the fraction of MasRs recycled back to the plasma membrane was smaller in SHR than in WKY neurons. Surprisingly, in SHR neurons but not in WKY neurons, Ang-(1-7) induced MasR translocation to the nucleus. Nuclear MasR expression and Ang-(1-7) levels were significantly greater in the nuclei of Ang-(1-7)-stimulated SHR neurons, indicating that the MasR is translocated with its ligand bound to it., Conclusion: MasRs display differential trafficking in brainstem neurons from SHRs, which may contribute to the impaired responses to Ang-(1-7)., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2019. For permissions, please email: journals.permissions@oup.com.)

Diabetes increases the risk of cardiovascular complications, including heart failure, hypertension, and stroke. There is a strong involvement of autonomic dysfunction in individuals with diabetes that exhibit clinical manifestations of cardiovascular diseases (CVD). Still, the mechanisms by which diabetes and its treatments alter autonomic function and subsequently affect cardiovascular complications remain elusive. For this reason, understanding the brainstem circuits involved in sensing metabolic state(s) and enacting autonomic control of the cardiovascular system are important to develop more comprehensive therapies for individuals with diabetes at increased risk for CVD. We review how autonomic nervous system circuits change during these disease states and discuss their potential role in current pharmacotherapies that target diabetic states. Overall, this review proposes that the brainstem circuits provide an integrative sensorimotor network capable of responding to metabolic cues to regulate cardiovascular function and this network is modified by, and in turn affects, diabetes-induced CVD and its treatment., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Rett Syndrome (RTT) is an X-linked neurodevelopmental disorder caused mainly by mutations in the MECP2 gene. One of the major RTT features is breathing dysfunction characterized by periodic hypo- and hyperventilation. The breathing disorders are associated with increased brainstem neuronal excitability, which can be alleviated with GABA agonists. Since neuronal hypoexcitability occurs in the forebrain of RTT models, it is necessary to find pharmacological agents with a relative preference to brainstem neurons. Here we show evidence for the improvement of breathing disorders of Mecp2-disrupted mice with the brainstem-acting drug cloperastine (CPS) and its likely neuronal targets. CPS is an over-the-counter cough medicine that has an inhibitory effect on brainstem neuronal networks. In Mecp2-disrupted mice, CPS (30 mg/kg, i.p.) decreased the occurrence of apneas/h and breath frequency variation. GIRK currents expressed in HEK cells were inhibited by CPS with IC 50 1 μM. Whole-cell patch clamp recordings in locus coeruleus (LC) and dorsal tegmental nucleus (DTN) neurons revealed an overall inhibitory effect of CPS (10 μM) on neuronal firing activity. Such an effect was reversed by the GABA A receptor antagonist bicuculline (20 μM). Voltage clamp studies showed that CPS increased GABAergic sIPSCs in LC cells, which was blocked by the GABA B receptor antagonist phaclofen. Functional GABAergic connections of DTN neurons with LC cells were shown. These results suggest that CPS improves breathing dysfunction in Mecp2-null mice by blocking GIRK channels in synaptic terminals and enhancing GABA release., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

DJ-1 (also known as PARK7) is a redox-active protein that protects against oxidative stress. This study evaluated the hypothesis that DJ-1 sustains brainstem cardiovascular regulation via maintaining mitochondrial function in the rostral ventrolateral medulla (RVLM), a brainstem site known to maintain blood pressure and sympathetic vasomotor tone, during cardiovascular depression elicited by the organophosphate insecticide mevinphos. In Sprague-Dawley rats, intravenous administration of mevinphos (640 μg kg -1 ) resulted in progressive hypotension, accompanied by an increase (Phase I) followed by a decrease (Phase II) of an experimental index for spontaneous baroreflex-mediated sympathetic vasomotor tone, alongside elevation in mitochondrial superoxide levels in the RVLM. There was concurrent activation of DJ-1 induced by oxidative stress in the RVLM, which was causally and temporally related to translocation of DJ-1 to mitochondria, reduction in mitochondrial membrane potential, increase in cytosolic apoptosis-inducing factor level, and apoptotic cell death in this brainstem site. Loss-of-function by immunoneutralization of DJ-1 in the RVLM significantly exacerbated those biochemical and cellular events, enhanced the progressive hypotension, diminished the increased and augmented the decreased spontaneous baroreflex-mediated sympathetic vasomotor tone respectively during Phases I and II, and heightened lethality during mevinphos intoxication. We conclude that DJ-1 in the RVLM sustains brainstem cardiovascular regulation induced by mevinphos via maintaining mitochondrial function., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Metabolic syndrome (MetS) is a common disorder that is associated with hypertension and poses a significant cardiovascular risk. Deactivation of extra-neuronal norepinephrine is mediated by catechol-O-methyltransferase (COMT). Endogenous 2-methoxyestradiol (2ME) is a product of COMT activity. The current study investigated the impact of 2ME on MetS-induced hypertension and the possible alterations in COMT expression and activity in rats. Animals were randomly divided into 4 groups. Group 1 received drinking water and standard food pellets. Groups 2, 3 and 4 were subjected to experimental induction of MetS. Animals in groups 3 and 4 were given daily IP injection of 2ME (25 and 50 mg/kg, respectively). MetS animals showed significant increases in body weight gain and visceral fat, fasting blood glucose and serum insulin and insulin resistance. Meanwhile, MetS was associated with a significant hypertriglyceridemia. Further, MetS significantly increased systolic, diastolic and mean arterial blood pressure. These effects were associated with significant reduction in COMT expression in the liver, kidneys and aorta as well as reduced hepatic activity. 2ME inhibited the alterations in body weight gain, visceral fat accumulation, fasting blood glucose and serum insulin, insulin resistance and serum triglycerides. Elevations in blood pressure were significantly inhibited by 2ME. Also, it attenuated the decrease in liver, kidney and aorta COMT expression and hepatic COMT activity. MetS was associated with elevated epinephrine and norepinephrine levels. Only the higher dose of 2ME significantly mitigated the rise in epinephrine level. In conclusion, 2ME protects against MetS-induced hypertension and averts COMT inhibited expression and activity., (Copyright © 2020 Elsevier B.V. All rights reserved.)