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This is a case report of an 81-year-old woman who underwent tracheostomy, bilateral cervical dissection, partial tongue resection, radial forearm free flap reconstruction, and split-thickness skin grafting under general anesthesia. After successful surgery, she was moderately sedated postoperatively with intravenous dexmedetomidine (DEX) and fentanyl. The fentanyl was discontinued 5 hours postoperatively. Eight hours after the operation, an atrioventricular junctional rhythm, a 2-mm elevation of the ST segment, and biphasic T waves were detected in lead II that lasted approximately 3 minutes. Hypotension and bradycardia were observed simultaneously with the abnormal electrocardiogram. The next day, a cardiologist examined the patient and suggested that coronary spasm had occurred based on those findings. The transient coronary spasm was likely caused by a combination of various factors including surgical stress and altered autonomic function. However, it is possible that stimulation of α-2 adrenergic receptors induced by DEX may also be linked to the coronary vasospasm that occurred.

The release of excessive amounts of catecholamine by pheochromocytoma–paragangliomas (PPGL) can lead to life-threatening catecholamine-induced cardiomyopathy (CIC). Single-nucleotide polymorphisms of the beta1 and alpha-2c adrenergic receptors alter myocyte receptor function and enhanced norepinephrine release. We tested the hypothesis that such genetic variations may impact the risk of developing CIC in the context of PPGL. Thirty-one patients with PPGL, including nine with a history of CIC, were analyzed for alpha-2-adrenergic receptors: ADRA2C, beta-1 and beta-2 adrenergic receptors: ADRB1 and ADRB2 genotyping. CIC was defined either by a history of heart failure or cardiogenic shock associated with dilated or Takotsubo cardiomyopathy. Subjects were genotyped for ADRA2C (rs61767072 for del322_325), ADRB1 (rs1801252 for Ser49Gly and rs1801253 for Arg389Gly) and ADRB2 (rs1042713 for Arg16Gly and rs1042714 for Gln27Glu). Single-locus analysis revealed that variant in ADRA2C (alpha 2CDel322–325) was more common among patients with CIC than among controls (allele frequency, 0.44 vs 0.05; P< 0.001). The lack of alpha 2CDel322–325 polymorphism has a negative predictive value of 95% for the onset of CIC. In a replication cohort including 26 patients with PPGL whom eight have developed a CIC, the association between Alpha 2CDel322–325 and CIC was confirmed (allele frequency, 0.33 vs 0.; P= 0.0001). In conclusion, Alpha 2CDel322–325 through the identification of patients at low risk of developing CIC can help physicians to better determine the most appropriate therapeutic approach, notably in patients at high risk of surgical complications.

Aims The α2‐adrenergic receptor (α2‐AR) agonists have been shown to be effective in the treatment of various pain. For example, dexmedetomidine (DEX), a selective α2A‐AR agonist, can be used for peripheral analgesia. However, it is not yet fully elucidated for the precise molecular mechanisms. P2X3 receptor is a major receptor processing nociceptive information in primary sensory neurons. Herein, we show that a functional interaction of α2A‐ARs and P2X3 receptors in dorsal root ganglia (DRG) neurons could contribute to peripheral analgesia of DEX. Methods Electrophysiological recordings were carried out on rat DRG neurons, and nociceptive behavior was quantified in rats. Results The activation of α2A‐ARs by DEX suppressed P2X3 receptor‐mediated and α,β‐methylene‐ATP (α,β‐meATP)‐evoked inward currents in a concentration‐dependent and voltage‐independent manner. Pre‐application of DEX shifted the α,β‐meATP concentration‐response curve downwards, with a decrease of 50.43 ± 4.75% in the maximal current response of P2X3 receptors to α,β‐meATP in the presence of DEX. Suppression of α,β‐meATP‐evoked currents by DEX was blocked by the α2A‐AR antagonist BRL44408 and prevented by intracellular application of the Gi/o protein inhibitor pertussis toxin, the adenylate cyclase activator forskolin, and the cAMP analog 8‐Br‐cAMP. DEX also suppressed α,β‐meATP‐evoked action potentials through α2A‐ARs in rat DRG neurons. Finally, the activation of peripheral α2A‐ARs by DEX had an analgesic effect on the α,β‐meATP‐induced nociception. Conclusions These results suggested that activation of α2A‐ARs by DEX suppressed P2X3 receptor‐mediated electrophysiological and behavioral activity via a Gi/o proteins and cAMP signaling pathway, which was a novel potential mechanism underlying analgesia of peripheral α2A‐AR agonists., The α2A‐adrenergic receptors (α2A‐ARs) primarily couple the Gi/o subtype of G‐protein family, which can inhibit intracellular adenylyl cyclase (AC), resulting in the decrease in cAMP levels and PKA activity. The activation of α2A‐ARs by dexmedetomidine (DEX) suppressed P2X3 receptors via the signaling pathway in rat DRG neurons. As a result of DEX treatment, α,β‐methylene‐ATP (α,β‐meATP), a P2X3 receptor agonist, evoked a reduced membrane current and then a decreased burst of action potentials (APs), leading to a relief of α,β‐meATP‐induced pain.

The purpose of this study was to investigate the effects of α

Dexmedetomidine (DEX), the most specific αWe used SMMC-7721 cells, MHCC97-H cells, and a mouse model of orthotopic hepatic carcinoma to explore the effect of DEX on angiogenesis and vasculogenic mimicry (VM) and its mechanism. Under normoxic (20% OThe results showed that DEX promoted angiogenesis and VM in human liver cancer cells within a certain dose range, and the addition of yohimbine inhibited this effect. DEX could activate HIF-1α/VEGFA pathway, which was further verified by silencing HIF-1α. Consistently,We believe that HIF-1α/VEGFA might be an important signaling pathway by which DEX promotes angiogenesis and VM formation in human hepatocellular carcinoma, whereas α

Cerebellar Purkinje cells (PCs) exhibit two types of discharge activities: simple spike (SS) and complex spike (CS). Previous studies found that noradrenaline (NA) can inhibit CS and bidirectionally regulate SS, but the enhancement of NA on SS is overwhelmed by the strong inhibition of excitatory molecular layer interneurons. However, the mechanism underlying the effect of NA on SS discharge frequency is not clear. Therefore, in the present study, we examined the mechanism underlying the increasing effect of NA on SS firing of PC in mouse cerebellar cortex in vivo and in cerebellar slice by cell-attached and whole-cell recording technique and pharmacological methods. GABA

Patients with chronic pain exhibit anxiety and deficits in memory. Additionally, α

The nucleus accumbens shell (NAcSh) receives extensive monoaminergic input from multiple midbrain structures. However, little is known how norepinephrine (NE) modulates NAc circuit dynamics. Using a dynamic electrophysiological approach with optogenetics, pharmacology, and drugs acutely restricted by tethering (DART), we explored microcircuit-specific neuromodulatory mechanisms recruited by NE signaling in the NAcSh of parvalbumin (PV)-specific reporter mice. Surprisingly, NE had little direct effect on modulation of synaptic input at medium spiny projection neurons (MSNs). In contrast, we report that NE transmission selectively modulates glutamatergic synapses onto PV-expressing fast-spiking interneurons (PV-INs) by recruiting postsynaptically-localized α2-adrenergic receptors (ARs). The synaptic effects of α2-AR activity decrease PV-IN-dependent feedforward inhibition onto MSNs evoked via optogenetic stimulation of cortical afferents to the NAcSh. These findings provide insight into a new circuit motif in which NE has a privileged line of communication to tune feedforward inhibition in the NAcSh.SIGNIFICANCE STATEMENTThe nucleus accumbens (NAc) directs reward-related motivational output by integrating glutamatergic input with diverse neuromodulatory input from monoamine centers. The present study reveals a synapse-specific regulatory mechanism recruited by norepinephrine (NE) signaling within parvalbumin-expressing interneuron (PV-IN) feedforward inhibitory microcircuits. PV-IN-mediated feedforward inhibition in the NAc is instrumental in coordinating NAc output by synchronizing the activity of medium spiny projection neurons (MSNs). By negatively regulating glutamatergic transmission onto PV-INs via α2-adrenergic receptors (ARs), NE diminishes feedforward inhibition onto MSNs to promote NAc output. These findings elucidate previously unknown microcircuit mechanisms recruited by the historically overlooked NE system in the NAc.

Identification of physiologically relevant targets for lead compounds emerging from drug discovery screens is often the rate-limiting step toward understanding their mechanism of action and potential for undesired off-target effects. To this end, we developed a streamlined chemical proteomic approach utilizing a single, photoreactive cleavable chloroalkane capture tag, which upon attachment to bioactive compounds facilitates selective isolation of their respective cellular targets for subsequent identification by mass spectrometry. When properly positioned, the tag does not significantly affect compound potency and membrane permeability, allowing for binding interactions with the tethered compound (probe) to be established within intact cells under physiological conditions. Subsequent UV-induced covalent photo-cross-linking "freezes" the interactions between the probe and its cellular targets and prevents their dissociation upon cell lysis. Targets cross-linked to the capture tag are then efficiently enriched through covalent capture onto HaloTag coated beads and subsequent selective chemical release from the solid support. The tag's built-in capability for selective enrichment eliminates the need for ligation of a capture tag, thereby simplifying the workflow and reducing variability introduced through additional operational steps. At the same time, the capacity for adequate cross-linking without structural optimization permits modular assembly of photoreactive chloroalkane probes, which reduces the burden of customized chemistry. Using three model compounds, we demonstrate the capability of this approach to identify known and novel cellular targets, including those with low affinity and/or low abundance as well as membrane targets with several transmembrane domains.

Atrial fibrillation (AF) from elevated adrenergic activity may involve increased atrial L-type Ca

Abnormalities in the cardiac sympathetic innervation and tone, as well as in the noradrenergic system are associated, among other peripheral complications, with diabetes mellitus. Furthermore, B-HT 933, an agonist at α

Dexmedetomidine is titrated to achieve sedation in the pediatric and cardiovascular intensive care units (PICU and CVICU). In adults, dexmedetomidine response has been associated with an ADRA2A polymorphism (rs1800544); CC genotype is associated with an increased sedative response compared with GC and GG. To date, this has not been studied in children.We conducted a pilot study to determine whether ADRA2A genotype is associated with dexmedetomidine dose in children.Forty intubated PICU or CVICU patients who received dexmedetomidine as a continuous infusion for at least 2 days were genotyped for ADRA2A with a custom-designed TaqMan® Assay. Ten (25%) subjects were wildtype (GG), 15 (37.5%) were heterozygous (GC), and 15 (37.5%) were homozygous (CC) variant. The maximum dexmedetomidine doses (mCg/kg/h) were not different between genotype groups CC (1, 0.3-1.2), GC (1, 0.3-1.3), and GG (0.8, 0.3-1.2), (p = 0.37); neither were mean dexmedetomidine doses for these respective genotype groups 0.68 (0.24-1.07), 0.72 (0.22-0.98), 0.58 (0.3-0.94), (p = 0.67).These findings did not confirm the results from adult studies where ADRA2A polymorphisms correlate with dexmedetomidine response, therefore highlighting the need for pediatric studies to validate PGx findings in adults prior to implementation in pediatrics.

We studied the effect of α

Dopamine levels in the central nervous system change under pathological conditions such as Parkinson's disease, Huntington's disease, and addiction. Under those pathological conditions, astrocytes become reactive astrocytes characterized by morphological changes and the release of inflammatory cytokines involved in pathogenesis. However, it remains unclear whether dopamine regulates astrocytic morphology and functions. Elucidating these issues will help us to understand the pathogenesis of neurodegenerative diseases caused by abnormal dopamine signaling. In this study, we investigated the effects of dopamine on IL-6 expression and process formation in rat primary cultured astrocytes and acute hippocampal slices. Dopamine increased IL-6 expression in a concentration-dependent manner, and this was accompanied by CREB phosphorylation. The effects of a low dopamine concentration (1 μM) were inhibited by a D1-like receptor antagonist, whereas the effects of a high dopamine concentration (100 μM) were inhibited by a β-antagonist and enhanced by a D2-like receptor antagonist. Furthermore, dopamine (100 μM) promoted process formation, which was inhibited by a β-antagonist and enhanced by both an α-antagonist and a D2-like receptor antagonist. In acute hippocampal slices, both a D1-like receptor agonist and β-agonist changed astrocytic morphology. Together, these results indicate that dopamine promotes IL-6 expression and process formation via D1-like receptors and β-adrenoceptors. Furthermore, bidirectional regulation exists; namely, the effects of D1-like receptors and β-adrenoceptors were negatively regulated by D2-like receptors and α

The pharmacological profile of tasipimidine, a novel orally active α

The primary kratom alkaloid mitragynine is proposed to act through multiple mechanisms, including actions at

The study examined the effect of α2-adrenoreceptor (α2-AR) activation against the background of preliminary blockage of If on the performance of Langerndorff-isolated rat heart. Stimulation of α2-AR in isolated rat hearts against the background of ZD7288 in concentrations of 10-9 M and 3×10-5 M changed the negative dynamics of myocardial inotropy to positive (by 25 and 38%; p

Norepinephrine is one of the key neurotransmitters in the hippocampus, but its role in the functioning of the neuroglial networks remains unclear. Here we show that norepinephrine suppresses NH4 Cl-induced oscillations of the intracellular Ca2+ concentration ([Ca2+ ]i ) in hippocampal neurons. We found that the inhibitory effect of norepinephrine against ammonium-induced [Ca2+ ]i oscillations is mediated by activation of alpha-2 adrenergic receptors. Furthermore, UK 14,304, an agonist of alpha-2 adrenergic receptors, evokes a biphasic [Ca2+ ]i elevation in a minor population of astrocytes. This elevation consists of an initial fast, peak-shaped [Ca2+ ]i rise, mediated by Giβγ subunit and subsequent PLC-induced mobilization of Ca2+ from internal stores, and a plateau phase, mediated by a Ca2+ influx from the extracellular medium through store-operated and TRPC3 channels. We show the correlation between the Ca2+ response in astrocytes and suppression of [Ca2+ ]i oscillations in neurons. The inhibitory effect of UK 14,304 is abolished in the presence of gallein, an inhibitor of Gβγ -signaling. In turn, application of the agonist in the presence of the PLC inhibitor decreases the frequency and amplitude of [Ca2+ ]i oscillations in neurons but does not suppress them. The same effect is observed in the presence of bicuculline, a GABA(A) receptor antagonist. We demonstrate that UK 14,304 application increases the frequency and amplitude of slow outward chloride currents in neurons, indicating the release of GABA by astrocytes. Thus, our findings indicate that the activation of astrocytic alpha-2 adrenergic receptors stimulates GABA release from astrocytes via Giβγ subunit-associated signaling pathway, contributing to the suppression of neuronal activity.

Chemical cross-linking would conceivably cause structural disruption of a protein, but few cross-linkers have been fully evaluated in this aspect. Furthermore, integral membrane proteins may differ from soluble proteins in the selection of suitable cross-linkers, which has never been investigated. In this study, we systematically evaluated the impact of five conventional cross-linkers targeting Lys, Asp and Glu, and two Arg-reactive cross-linkers on the structural and functional integrity of two G protein-coupled receptors (GPCRs). Perturbation of the receptor structure and ligand-binding activity was observed, depending on the receptor and cross-linking conditions. In particular, our study demonstrated that the concentrations of PDH and KArGO need to be fine-tuned in order to minimize the structural and functional disturbance of specific GPCRs. A set of amenable cross-linkers was selected to acquire the most comprehensive cross-link maps for two GPCRs. Our in-depth cross-linking mass spectrometry (CXMS) analysis has revealed dynamic features of structural regions in GPCRs that are not observable in the crystal structures. Thus, CXMS analysis of GPCRs using the expanded toolkit would facilitate structural modeling of uncharacterized receptors and gain new insights into receptor-ligand interactions.

The molecular mechanisms underlying the anterograde surface transport of G protein-coupled receptors (GPCRs) after their synthesis in the endoplasmic reticulum (ER) are not well defined. In C. elegans, odorant response abnormal 4 has been implicated in the delivery of olfactory GPCRs to the cilia of chemosensory neurons. However, the function and regulation of its human homolog, C1orf27, in GPCR transport or in general membrane trafficking remain unknown. Here, we demonstrate that siRNA-mediated knockdown of C1orf27 markedly impedes the ER-to-Golgi export kinetics of newly synthesized α

Vascular smooth muscle cell (VSMC) phenotypic modulation regulates the initiation and progression of intracranial aneurysm (IA). Dexmedetomidine (DEX) is suggested to play neuroprotective roles in patients with craniocerebral injury. Therefore, we investigated the biological functions of DEX and its mechanisms against IA formation and progression in the current study. The rat primary VSMCs were isolated from Sprague–Dawley rats. IA and superficial temporal artery (STA) tissue samples were obtained from patients with IA. Flow cytometry was conducted to identify the characteristics of isolated VSMCs. Hydrogen peroxide (H2O2) was used to mimic IA-like conditions in vitro. Cell viability was detected using CCK-8 assays. Wound healing and Transwell assays were performed to detect cell motility. ROS production was determined by immunofluorescence using DCFH-DA probes. Western blotting and RT-qPCR were carried out to measure gene expression levels. Inflammation responses were determined by measuring inflammatory cytokines. Immunohistochemistry staining was conducted to measure α2-adrenergic receptor levels in tissue samples. DEX alleviated the H2O2-induced cytotoxicity, attenuated the promoting effects of H2O2 on cell malignancy, and protected VSMCs against H2O2-induced oxidative damage and inflammation response. DEX regulated the GSK-3β/MKP-1/NRF2 pathway via the α2AR. DEX alleviates the inflammatory responses and oxidative damage of VSMCs by regulating the GSK-3β/MKP-1/NRF2 pathway via the α2AR in IA.

Ligand binding to G protein–coupled receptors (GPCRs), such as the α

Here is reported the design and synthesis of a series of highly potent and selective α2C antagonists using benzodioxine methyl piperazine as a central scaffold by pharmacophoric analysis to improve the pharmacokinetics of suboptimal clinical candidate molecules.

As one of the nine subtypes of adrenergic receptors (ARs) in the brain, α2C-ARs play essential roles in emotion and memory, and are implicated in neuropsychiatric disorders, including depression, Alzheimer's disease, substance use disorder, and schizophrenia. A recently developed α2C-AR specific positron emission tomography (PET) radiotracer, [

The 2-pentadecyl-2-oxazoline (PEA-OXA) is a natural compound with protective action in neuro-inflammation. We have previously shown that PEA-OXA behaves as an α2 adrenergic receptor (α2AR) antagonist and a putative protean agonist on histamine H3 receptors. Recently, neuroinflammation and monoaminergic neurotransmission dysfunction has drawn particular attention in Alzheimer Disease (AD) pathophysiology. In this context, the objective of this study was to investigate the effects of the dual-acting PEA-OXA in an AD-like model in mice. A combined computational and experimental approach was used to evaluate the ability of PEA-OXA to bind α2A-AR subtype, and to investigate the effects of PEA-OXA treatment on neuropathological (behavioural and functional) effects induced by soluble Amyloid β 1-42 (sAβ1-42) intracerebroventricular injection. Computational analysis revealed the PEA-OXA ability to bind the α2A-AR, a pharmacological target for AD, in two alternative poses, one overlapping the Na+ binding site. In vivo studies indicated that chronic treatment with PEA-OXA (10mg/kg, os) restored the cognitive (discriminative and spatial memory) deficits and social impairments induced by sAβ injection. Consistently, electrophysiological analysis showed a recovery of the long-term potentiation in the hippocampus (Lateral Entorhinal Cortex-Dentate Gyrus pathway), while neuroinflammation, i.e., increased pro-inflammatory cytokines levels and microglia cells density were reduced. These data provide the basis for further investigation of the pro-cognitive aptitude of PEA-OXA by proposing it as an adjuvant in the treatment in AD, for which the available pharmacological approaches remain unsatisfactory. Moreover, this study offers new future direction in research investigating the role of α2AR in neuropsychiatric illness and therapies.

Noradrenergic control is very significant for the contractility of healthy and inflamed uteri. The receptor mechanisms of noradrenaline (NA) influencing the contractile activity of an inflamed uterus are poorly recognized. This study was undertaken to determine the participation of α2-adrenergic receptors (ARs) isoforms (A, B, C) in NA-evoked contractility of the pig uterus with severe acute endometritis. Saline (SAL group) or E.coli suspension (E.coli group) were injected into uterine horns, while only laparotomy was performed in the CON group. In relation to the period before NA application, NA decreased the tension, amplitude and frequency in the uterine strips of the CON and SAL groups, and the amplitude and frequency in the E.coli group. In the E.coli group, the amplitude and frequency were lower than in other groups. Compared to NA effect alone, a greater reduction or appearance of a decrease in the amplitude and frequency were noted in all groups following the use of selective α2A- and α2C-ARs antagonists together with NA as well as in the tension in the CON and SAL groups in response to an α2C-ARs antagonist and NA. Such effects were also exerted by an α2B-ARs antagonist with NA on the frequency in all groups and on the amplitude in the CON and SAL groups. To sum up, in an inflammatory-changed porcine uterus, three α2-AR isoforms mediate the effect of NA on contractile frequency, while α2A- and α2C-AR are involved in the control of contractile amplitude. These results could offer new targets for drugs against decreased uterine contractility in inflammation.

Neurochemical, electrophysiological and behavioral evidence indicate that the potent α

Depression is associated with thrombotic risk and arterial events, its proper management is strongly recommended in coronary artery disease (CAD) patients. We have previously shown that the Brain-Derived Neurotrophic Factor (BDNF)Val66Met polymorphism, related to depression, is associated with arterial thrombosis in mice, and with an increased risk of acute myocardial infarction in humans. Herein, expanding the previous findings on BDNFVal66Met polymorphism, we show that desipramine, a norepinephrine reuptake-inhibitor, rescues behavioral impairments, reduces the arterial thrombosis risk, abolishes pathological coagulation and platelet hyper-reactivity, normalizes leukocyte, platelet, and bone marrow megakaryocyte number and restores physiological norepinephrine levels in homozygous knock-in BDNF Val66Met (BDNF

The stimulation of α

Increased sympathetic nerve excitability has been reported to aggravate a variety of chronic pain conditions, and an increase in the number of sympathetic nerve fibers in the dorsal root ganglion (DRG) has been found in neuropathic pain (NP) models. However, the mechanism of the neurotransmitter norepinephrine (NE) released by sympathetic nerve fiber endings on the excitability of DRG neurons is still controversial, and the adrenergic receptor subtypes involved in this biological process are also controversial. In our study, we have two objectives: (1) To determine the effect of the neurotransmitter NE on the excitability of different neurons in DRG; (2) To determine which adrenergic receptors are involved in the excitability of DRG neurons by NE released by sprouting sympathetic fibers. In this experiment, a unique field potential recording method of spinal cord dorsal horn was innovatively adopted, which can be used for electrophysiological study in vivo. The results showed that： Forty days after SNI, patch clamp and field potential recording methods confirmed that NE enhanced the excitability of ipsilateral DRG large neurons, and then our in vivo electrophysiological results showed that the α2 receptor blocker Yohimbine could block the excitatory effect of NE on A-fiber and the inhibitory effect on C-fiber, while the α2A-adrenergic receptor agonist guanfacine (100 μM) had the same biological effect as NE. Finally, we concluded that NE from sympathetic fiber endings is involved in the regulation of pain signaling by acting on α2A-adrenergic receptors in DRG.

Topical α1- and α2-adrenoreceptor (ADRA1 and 2) agonists are effective in alleviating permanent vasodilation and facial erythema associated with rosacea by inducing skin vasoconstriction. Although β-adrenoreceptor (ADRB) antagonists are used off-label for rosacea, pharmacological and pharmacodynamic data pertaining to these receptors in skin micro-vessels are lacking. Objectives: To analyse the expression of different adrenergic receptors and their contribution to vasoreactivity in skin micro-vessels. Small arteries (500-800 μm) and arterioles (

Background: Attention-deficit hyperactivity disorder (ADHD) is the most common childhood-onset neurodevelopmental disorder, and methylphenidate (MPH) is considered one of the first-line medicine for ADHD. Unfortunately, this medication is only effective for some children with ADHD. This meta-analysis was conducted to evaluate whether noradrenergic gene polymorphisms impact the efficacy of MPH in children with ADHD. Methods: Candidate gene studies published in English until March 1, 2020, were identified through literature searches on PubMed, Web of Science, and Embase. Data were pooled from individual clinical trials considering MPH pharmacogenomics. According to the heterogeneity, the odds ratio and mean differences were calculated by applying fixed-effects or random-effects models. Results: This meta-analysis includes 15 studies and 1382 patients. Four polymorphisms of the NET gene (rs5569, rs28386840, rs2242446, rs3785143) and 2 polymorphisms of the α2A-adrenergic receptor gene (ADRA2A) gene (MspI and DraI) were selected for the analysis. In the pooled data from all studies, T allele carriers of the rs28386840 polymorphism were significantly more likely to respond to MPH (P

We have investigated the interaction of α

α-adrenergic receptors (αARs) are G protein-coupled receptors that regulate vital functions of the cardiovascular and nervous systems. The therapeutic potential of αARs, however, is largely unexploited and hampered by the scarcity of subtype-selective ligands. Moreover, several aminergic drugs either show off-target binding to αARs or fail to interact with the desired subtype. Here, we report the crystal structure of human α1BAR bound to the inverse agonist (+)-cyclazosin, enabled by the fusion to a DARPin crystallization chaperone. The α1BAR structure allows the identification of two unique secondary binding pockets. By structural comparison of α1BAR with α2ARs, and by constructing α1BAR-α2CAR chimeras, we identify residues 3.29 and 6.55 as key determinants of ligand selectivity. Our findings provide a basis for discovery of α1BAR-selective ligands and may guide the optimization of aminergic drugs to prevent off-target binding to αARs, or to elicit a selective interaction with the desired subtype., This study reports the X-ray structure of the α1B-adrenergic G protein-coupled receptor bound to an inverse agonist, and unveils key determinants of subtype-selective ligand binding that may help the design of aminergic drugs with fewer side-effects.

Musculoskeletal and psychological complaints have increased with the widespread use of visual display terminals, and musculoskeletal pain is known to be closely related to stress. One method of experimentally inducing persistent muscle pain is repeated cold stress (RCS), and animals exposed to such stress exhibit a dysfunction in the descending pain inhibitory system. Acetaminophen (N-acetyl-p-aminophenol; APAP) is widely used to relieve several types of pain, including musculoskeletal pain, and is available as an OTC drug. However, the mechanism underlying its analgesic action has not yet been fully elucidated. In this study, we compared the analgesic effect of APAP on RCS-induced muscular hyperalgesia with those of other analgesics to identify its mechanism of action. The daily oral administration of APAP significantly suppressed the decrease in the mechanical withdrawal threshold caused by RCS, similar to the results for neurotropin but not for the cyclooxygenase inhibitor ibuprofen (IBP). Moreover, the intrathecal administration of antagonists of the 5-hydroxytryptamine (5-HT)

The concentration dependenies of the chronotropic response and changes in blood supply to the isolated heart of 7-day-old newborn rats induced by application of α2-adrenergic receptor agonist clonidine hydrochloride in concentrations of 10

Aims To investigate the mechanism of action of 55P0251, a novel multiflorine‐derived substituted quinazolidine that augments insulin release and lowers blood glucose in rodents, but does not act via mechanisms addressed by any antidiabetic agent in clinical use. Materials and Methods Using male mice, we determined the effects of 55P0251 on glucose tolerance, insulin secretion from isolated islets and blood oxygen saturation, including head‐to‐head comparison of 55P0251 to its inverted enantiomer 55P0250, as well as to other anti‐hyperglycaemic multiflorine derivatives discovered in our programme. Results 55P0251 was clearly superior to its inverted enantiomer in the glucose tolerance test (area under the curve: 11.3 mg/kg 55P0251, 1.19 ± 0.04 min*mol/L vs 55P0250, 1.80 ± 0.04 min*mol/L; P

Environmental cues can elicit robust cocaine reward memories, contributing to relapse to cocaine abuse. Memories can be manipulated pharmacologically by interfering with reconsolidation after reactivation. Clonidine, an α2 noradrenergic receptor agonist, was tested for its ability to block reconsolidation of cocaine environmental-paired memory. Male Sprague-Dawley rats completed an 8-day cocaine place conditioning procedure to establish a cocaine place preference. Cocaine memory was reactivated by exposure to the cocaine-paired environment in a drug-free state, followed immediately by administration of clonidine (10 or 50 µg/kg) or vehicle. Cocaine place preference was retested 24 h and 1 week later. Clonidine significantly attenuated the previously established cocaine place preference when tested 1 or 7 days later. To investigate the generalizability of this effect to other drug classes, morphine conditioned place preference was tested. Clonidine administration after morphine memory reactivation did not significantly alter the expression of morphine place preference. These results suggest that clonidine can interfere with reconsolidation of cocaine memory and may be a useful approach to reduce relapse.

Breast cancer is the most frequently diagnosed and leading cause of cancer death among women worldwide. It was classified within molecular intrinsic subtypes: luminal A, luminal B, human epidermal growth factor receptor 2‐enriched and basal‐like. Epinephrine and norepinephrine, released during stress, bind to adrenoceptors. α2‐adrenoceptors are encoded by the ADRA2A , ADRA2B and ADRA2C genes and β2 by ADRB2 . Fil: Rivero, Ezequiel Mariano. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina Fil: Martinez, Leandro Marcelo. Hospital for Special Surgery; Estados Unidos Fil: Bruque, Carlos David. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Dirección Nacional de Instituto de Investigación. Administración Nacional de Laboratorio e Instituto de Salud "Dr. C. G. Malbrán"; Argentina Fil: Gargiulo, Lucía. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina Fil: Bruzzone, Ariana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones Bioquímicas de Bahía Blanca. Universidad Nacional del Sur. Instituto de Investigaciones Bioquímicas de Bahía Blanca; Argentina Fil: Luthy, Isabel Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Alpha 2 (α2-) adrenoceptor agonists, such as clonidine or dexmedetomidine, have been found to inhibit hyperpolarization-activated, cyclic nucleotide-modulated (HCN) channels, not only by reducing intracellular cyclic AMP levels but also by directly blocking HCN channels. In this study, we examined the inhibitory effect of guanabenz, a centrally acting α2-adrenoceptor agonist with high specificity for α2A-subtype, on HCN channels in mesencephalic trigeminal nucleus (MTN) neurons which robustly express HCN channels and have been suggested to coexpress α2A-adrenoceptors. By performing whole-cell patch-clamp recording on MTN neurons in brainstem slices, hyperpolarization-activated inward current (Ih) was examined during guanabenz treatment. Guanabenz inhibited Ih in a dose-dependent manner, which was likely to be ZD7288-sensitive HCN current as it did not affect barium-sensitive inward rectifying potassium current. Guanabenz not only inhibited Ih but also shifted the voltage-dependent activation curve to hyperpolarizing potentials. Interestingly, Ih inhibition by guanabenz was not reversed by α2-adrenoceptor antagonist atipamezole treatment or by intracellular cyclic AMP perfusion, suggesting that the inhibition may not result from α2A-adrenoceptor signalling pathway but from direct inhibition of HCN channels. Coherent to our electrophysiological results, single-cell RT-PCR revealed that most MTN neurons lack α2A-adrenoceptor mRNA. Our study demonstrates that guanabenz can directly inhibit HCN channels in addition to its primary role of activating α2A-adrenoceptors.

α2-adrenoceptor (α2-AR) isoforms, abundant in sympathetic synapses and noradrenergic neurons of the central nervous system, are integral in the presynaptic feed-back loop mechanism that moderates norepinephrine surges. We recently identified that postsynaptic α2-ARs, found in the myocellular sarcolemma, also contribute to a muscle-delimited feedback control capable of attenuating mobilization of intracellular Ca2+ and myocardial contractility. This previously unrecognized α2-AR-dependent rheostat is able to counteract competing adrenergic receptor actions in cardiac muscle. Specifically, in ventricular myocytes, nitric oxide (NO) and cGMP are the intracellular messengers of α2-AR signal transduction pathways that gauge the kinase-phosphatase balance and manage cellular Ca2+ handling preventing catecholamine-induced Ca2+ overload. Moreover, α2-AR signaling counterbalances phospholipase C - PKC-dependent mechanisms underscoring a broader cardioprotective potential under sympathoadrenergic and angiotensinergic challenge. Recruitment of such tissue-specific features of α2-AR under sustained sympathoadrenergic drive may, in principle, be harnessed to mitigate or prevent cardiac malfunction. However, cardiovascular disease may compromise peripheral α2-AR signaling limiting pharmacological targeting of these receptors. Prospective cardiac-specific gene or cell-based therapeutic approaches aimed at repairing or improving stress-protective α2-AR signaling may offer an alternative towards enhanced preservation of cardiac muscle structure and function.

Previous reports suggest flavonoids as potent analgesic compounds. Based on these observations, the present study investigated the antinociceptive action of flavonol, 3′, 4′-dimethoxy flavonol, 6, 3′-dimethoxy flavonol, 7, 2′-dimethoxy flavonol, and 7, 3′-dimethoxy flavonol and the possible mechanisms involved in these effects. The antinociceptive effect of the investigated compounds in doses of 25, 50, 100, and 200 mg/kg was evaluated in male Swiss albino mice using the acetic acid test, formalin-induced nociception, and hot water tail immersion test. The role of opioid, tryptaminergic, adrenergic, dopaminergic, GABAergic, and K+ATP channels in producing the antinociceptive effect was also studied using appropriate interacting agents. Treatment with flavonol and dimethoxy flavonols resulted in a significant reduction in the number of abdominal constrictions in the acetic acid test, a significant inhibition of the paw-licking/biting response time in both the phases of formalin nociception and also a significant increase in mean reaction time in the hot water tail immersion test. These observations revealed the antinociceptive effect of dimethoxy flavonols. The role of opioid, serotonergic (5HT3), and dopaminergic system was identified in the antinociceptive effect of flavonol and all dimethoxy derivatives investigated. In addition, the role of GABAergic, K+ATP channel, and α-2 adrenergic mechanisms were also observed in the antinociceptive action of some of the investigated compounds. The present study identified the antinociceptive effect of flavonol and dimethoxy flavonols in mice acting through different neuronal pathways.

In addition to schizophrenia and bipolar disorder, aripiprazole is approved as an adjunct for major depressive disorder (MDD). Adding aripiprazole to the 5-HT reuptake inhibitor escitalopram reverses the inhibitory action of escitalopram on firing activity of rat 5-HT, norepinephrine (NE) and DA neurons. This study investigated how aripiprazole, escitalopram and their combination affect the net effect of 5-HT and NE neurotransmission in the rat hippocampus. Electrophysiological recordings of hippocampus CA3 pyramidal neurons were conducted in anesthetized Sprague-Dawley rats after 2- and 14-day administration regimens. Aripiprazole and escitalopram (2 and 5 mg/kg/day, respectively) were delivered alone or in combination through subcutaneous injections and implanted osmotic minipumps, respectively. Overall neurotransmission of 5-HT and NE were assessed by determining possible enhancements in tonic activation of 5-HT1A receptors and α1- and α2-adrenoceptors. This was achieved by assessing increases of firing rate of pyramidal neurons due to disinhibition induced by injections of antagonists for these three types of receptors. While neither 2- and 14-day administration of escitalopram nor aripiprazole significantly altered firing rate of pyramidal neurons following injection of 5-HT1A antagonist WAY100635, their combination for 14 days significantly increased this parameter. Fourteen days of the same drug regimens did not change firing following injection of the α1- and α2-adrenoceptor antagonists prazosin and idazoxan, respectively. A synergy between aripiprazole and escitalopram was thus documented by an increase in the tonic activation of 5-HT1A receptors after 14 days of administration that may account, at least in part, for the benefits of this strategy in MDD.

Dexmedetomidine (DEX) protects against liver damage caused by sepsis. The purpose of this study was to confirm the regulatory effects of DEX on glycogen synthase kinase 3 beta (GSK-3β) via the α2 adrenergic receptor (α2AR) and evaluate the role of GSK-3β in lipopolysaccharide (LPS)-induced liver injury. Sprague-Dawley (SD) rats were administered an intraperitoneal injection of DEX (30 μg/kg) 30 min before an intraperitoneal injection of LPS (10 mg/kg). HE staining and serum biochemical test results indicated that DEX significantly improved liver histopathological damage and liver function indices. Furthermore, DEX increased super oxide dismutase (SOD) activity and L-glutathione (GSH) levels, and inhibited malondialdehyde (MDA) production. Western blot (WB) analysis demonstrated that treatment with the GSK-3β inhibitor SB216763 increased antioxidant-related protein mitogen-activated protein kinase phosphatase 1 (MKP-1) and nuclear factor erythroid 2-related factor 2 (Nrf2) expression. In addition, anti-apoptosis-related proteins were up-regulated and pro-apoptosis-related proteins were down-regulated by SB21676 administration. WB analysis also showed that DEX increased anti-apoptosis-related protein levels and decreased pro-apoptotic protein levels in LPS-induced liver injury. Nrf2, p53, and activated caspase-3 levels were further evaluated using immunohistochemistry (IHC), producing results consistent with WB results. The α2AR antagonist atipamezole (AT) significantly reversed the protective effects of DEX, as shown by WB analysis. Our data suggested that α2AR plays an important role in reversing the effects of liver oxidative stress and apoptosis via DEX, and that DEX exerts antioxidant and anti-apoptosis effects through regulation of the GSK-3β/MKP-1/Nrf2 pathway.

Osteoarthritis (OA) is a debilitating conditioning with pain as the major clinical symptom. Understanding the mechanisms that drive OA-associated chronic pain is crucial for developing the most effective analgesics. Although the degradation of the joint is the initial trigger for the development of chronic pain, the discordance between radiographic joint damage and the reported pain experience in patients, coupled with clinical features that cannot be explained by purely peripheral mechanisms, suggest there are often other factors at play. Therefore, this study considers the central contributions of chronic pain, using a monoiodoacetate (MIA) model of OA. Particularly, this study explores the functionality of descending controls over the course of the model by assessing diffuse noxious inhibitory controls (DNIC). Early-phase MIA animals have a functional DNIC system, whereas DNIC are abolished in late-phase MIA animals, indicating a dysregulation in descending modulation over the course of the model. In early-phase animals, blocking the actions of spinal α2-adrenergic receptors completely abolishes DNIC, whereas blocking the actions of spinal 5-HT7 receptors only partially decreases the magnitude of DNIC. However, activating the spinal α2-adrenergic or 5-HT7 receptors in late-phase MIA animals restored DNIC-induced neuronal inhibition. This study confirms that descending noradrenergic signaling is crucial for DNIC expression. Furthermore, we suggest a compensatory increase in descending serotonergic inhibition acting at 5-HT7 receptors as the model progresses such that receptor activation is sufficient to override the imbalance in descending controls and mediate neuronal inhibition. NEW & NOTEWORTHY This study showed that there are both noradrenergic and serotonergic components contributing to the expression of diffuse noxious inhibitory controls (DNIC). Furthermore, although a tonic descending noradrenergic tone is always crucial for the expression of DNIC, variations in descending serotonergic signaling over the course of the model mean this component plays a more vital role in states of sensitization.

In this manuscript, we report a series of benzodioxine methyl piperidine derivatives as highly potent and selective α2C antagonists by ligand design to improve the pharmacokinetics of a previous candidate molecule.

Increased opioid synthesis and release, and enhanced alpha-2 adrenoceptor signaling have been suggested to mediate repeated oxytocin-induced long-lasting effects including elevated pain threshold in rats. This study evaluated whether oxytocin pretreatment would influence development of dependence and tolerance to the nociceptive and body temperature responses to morphine and enhance effects of alpha-2 adrenergic agonist clonidine on nociceptive threshold, body temperature and morphine withdrawal signs. Rats injected subcutaneously with saline or 1 mg/kg oxytocin for 5 days were implanted with placebo or morphine pellets 24 h after the treatment period. Body temperature and nociception were assessed, with nociception determined via by hot plate and tail immersion tests, before and 4, 24 and 48 h after pellet implantation, and following a challenge dose of morphine. Withdrawal signs were determined after naloxone administration. Oxytocin produced analgesia, as evidenced by increased paw withdrawal latency in the hot plate test. Morphine increased body temperature and nociceptive threshold which declined over time. Morphine challenge could not demonstrate tolerance to the body temperature response. Analgesic tolerance was observed in the hot plate test in saline and in both tests in oxytocin pretreated rats. Naloxone-precipitated withdrawal appeared to be less severe in oxytocin pretreatment. Clonidine was ineffective on the withdrawal signs but decreased body temperature and increased tail flick latency in the tail immersion test in oxytocin pretreated animals. These results, while producing evidence for a hyperresponsiveness in alpha-2 adrenoceptors, provide contrasting effects on morphine tolerance and dependence, and their partial mediation by opioidergic and adrenergic activation in repeated oxytocin treatment.

Levamisole, a veterinary anthelmintic drug, is one of the most widely used and dangerous cocaine adulterants. Like cocaine, levamisole acutely blocks noradrenaline reuptake but with much less potency, although its vascular effects are not well known. In this study, we evaluated the vascular effects of levamisole and cocaine in rabbit aortic rings used for isometric recording of tension in organ baths and protein expression by western blot. Our results indicated that levamisole (10

BACKGROUND Pridopidine, in development for Huntington's disease, may modulate aberrant l-dopa-induced effects including l-dopa-induced dyskinesia (LID). OBJECTIVE This study investigated whether pridopidine could reduce LID in the MPTP macaque model of Parkinson's disease and characterized the observed behavioral effects in terms of receptor occupancy. METHODS The pharmacokinetic profile and effects of pridopidine (15-30 mg/kg) on parkinsonism, dyskinesia, and quality of on-time, in combination with l-dopa, were assessed in MPTP macaques with LID. Pridopidine receptor occupancy was estimated using known in vitro binding affinities to σ1 and dopamine D2 receptors, in vivo PET imaging, and pharmacokinetic profiling across different species. RESULTS Pridopidine produced a dose-dependent reduction in dyskinesia (up to 71%, 30 mg/kg) and decreased the duration of on-time with disabling dyskinesia evoked by l-dopa by 37% (20 mg/kg) and 60% (30 mg/kg). Pridopidine did not compromise the anti-parkinsonian benefit of l-dopa. Plasma exposures following the ineffective dose (15 mg/kg) were associated with full σ1 occupancy (>80%), suggesting that σ1 engagement alone is unlikely to account for the antidyskinetic benefits of pridopidine. Exposures following effective doses (20-30 mg/kg), while providing full σ1 occupancy, provide only modest dopamine D2 occupancy (