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Controlled nigrostriatal dopamine release supports effective limb use during locomotion coordination that becomes compromised after this pathway deteriorates in Parkinson's Disease (PD). How dopamine release relates to active ongoing behavior control remains unknown. Restoring proper release strategy appears important to successful PD treatment with transplanted dopamine-producing stem cells. This is suggested by apparently distinct behavioral support from tonic or phasic release and corresponding requirements of requisite afferent control exhibited by intact nigrostriatal neurons. Our laboratory previously demonstrated that transplanted dopaminergic cells can elicit skilled movement recovery known to depend on phasic dopamine release. However, efforts to measure this movement-related dopamine release yielded seemingly paradoxical, incongruent results. In response, here we explored whether those previous observations derived from rapid reuptake transport into either transplanted cells or residual, lesion-surviving terminals. We confirmed this using minimal reuptake blockade during intrastriatal microdialysis. After unilateral dopamine depletion, rats received transplants and were subjected to our swimming protocol. Among dopamine-depleted and transplanted rats, treatment supported restoration of limb movement symmetry. Interestingly, subsequent reuptake-restricted microdialysis confirmed distinct swimming-induced dopamine increases clearly occurred among these lesioned/transplanted subjects. Thus, phasic firing control appears to contribute to transplant-derived recovery in Parkinsonian animals. • Nomifensine assists with observing dopamine and its breakdown using microdialysis. • Mesencephalic cells integrate in vivo without differentiation pre transplantation. • Transplant supported behavioral recovery occurs with frequent limb use and exercise. • Data shows raw dopamine increase with swimming control after transplants. • Behavioral recovery occurred over a short timeline post stem cell transplantation. [ABSTRACT FROM AUTHOR]

Paroxysmal nonkinesigenic dyskinesia (PNKD) is an autosomal dominant episodic movement disorder. Patients have episodes that last 1 to 4 hours and are precipitated by alcohol, coffee, and stress. Previous research has shown that mutations in an uncharacterized gene on chromosome 2q33-q35 (which is termed PNKD) are responsible for PNKD. Here, we report the generation of antibodies specific for the PNKD protein and show that it is widely expressed in the mouse brain, exclusively in neurons. One PNKD isoform is a membrane-associated protein. Transgenic mice carrying mutations in the mouse Pnkd locus equivalent to those found in patients with PNKD recapitulated the human PNKD phenotype. Staining for c-fos demonstrated that administration of alcohol or caffeine induced neuronal activity in the basal ganglia in these mice. They also showed nigrostriatal neurotransmission deficits that were manifested by reduced extracellular dopamine levels in the striatum and a proportional increase of dopamine release in response to caffeine and ethanol treatment. These findings support the hypothesis that the PNKD protein functions to modulate striatal neuro-transmitter release in response to stress and other precipitating factors.

Abstract Paraoxon is the active metabolite of parathion, an organophosphorus pesticide which can cause neurotoxic effects in animals and humans. In the present work, we investigated the effects of 5 mM paraoxon on striatal dopamine, DOPAC and HVA levels in conscious and freely moving rats, after treatment with TTX, reserpine, nomifensine, KCl, Ca++-free/EDTA medium, AP-5 or L-NAME. The intrastriatal administration of paraoxon for 60 min, through the microdialysis probe, significantly produced an increase of the dopamine to 1066 ± 120%, relative to basal levels. Administration of paraoxon to 20 μM TTX, 10 mg/kg reserpine or Ca++-free/EDTA medium-pretreated animals decreased the dopamine levels to 73%, 81%, and 70%, respectively, when compared with the effect of 5 mM paraoxon. Infusion of 50 μM nomifensine induced a maximal increase in extracellular dopamine levels to 1435 ± 387%, and when nomifensine was coadministered with paraoxon, striatal dopamine levels increased to 2429 ± 417%, an increase that was ∼230% higher that observed with the administration of the pesticide alone. Coinfusion of KCl and paraoxon produced an increase in extracellular dopamine to 1957 ± 445%, that was significantly higher than that observed with POX or KCl (1104 ± 220%) administered individually. Pretreatment with 650 μM AP-5 or 100 L-NAME reduced the effect of paraoxon on extracellular dopamine levels by 49.1% and 53.7%, respectively. Our results suggest that paraoxon induces dopamine release by a vesicular-, Ca++-, and deporalization-dependent mechanism, being independent of dopamine transporter. In addition, the paraoxon-induced dopamine release is mediated by glutamatergic and nitrergic neurotransmitter systems. Highlights • Paraoxon, an organophosphorous pesticide increased the striatal dopamine release. • The release of dopmanine is predominantly mediated by an vesicular, Ca2+-, and action potential-dependent mechanism. • Paraoxon also increases the release of dopamine stimulated by depolarization. • The release of dopamine induced by the paraoxon is partially mediated by the activation of NMDA glutamatergic receptors and the nitrergic neurons. [ABSTRACT FROM AUTHOR]

Human dopamine transporter (hDAT) regulates the reuptake of extracellular dopamine (DA) and is an essential therapeutic target for central nervous system (CNS) diseases. The allosteric modulation of hDAT has been identified for decades. However, the molecular mechanism underlying the transportation is still elusive, which hinders the rational design of allosteric modulators against hDAT. Here, a systematic structure-based method was performed to explore allosteric sites on hDAT in inward-open (IO) conformation and to screen compounds with allosteric affinity. First, the model of the hDAT structure was constructed based on the recently reported Cryo-EM structure of the human serotonin transporter (hSERT) and Gaussian-accelerated molecular dynamics (GaMD) simulation was further utilized for the identification of intermediate energetic stable states of the transporter. Then, with the potential druggable allosteric site on hDAT in IO conformation, virtual screening of seven enamine chemical libraries (∼440,000 compounds) was processed, resulting in 10 compounds being purchased for in vitro assay and with Z1078601926 discovered to allosterically inhibit hDAT (IC 50 = 0.527 [0.284; 0.988] μM) when nomifensine was introduced as an orthosteric ligand. Finally, the synergistic effect underlying the allosteric inhibition of hDAT by Z1078601926 and nomifensine was explored using additional GaMD simulation and postbinding free energy analysis. The hit compound discovered in this work not only provides a good starting point for lead optimization but also demonstrates the usability of the method for the structure-based discovery of novel allosteric modulators of other therapeutic targets.

Microdialysis is often applied to understanding brain function. Because neurotransmission involves rapid events, increasing the temporal resolution of in vivo measurements is desirable. Here, we demonstrate microdialysis with online capillary liquid chromatography for the analysis of 1 min rat brain dialysate samples at 1 min intervals. Mobile phase optimization involved adjusting the pH, buffer composition, and surfactant concentration to eliminate interferences with the dopamine peak. By analyzing electrically evoked dopamine transients carefully synchronized with the switching of the online LC sample valve, we demonstrate that our system has both 1 min sampling capabilities and bona fide 1 min temporal resolution. Evoked DA transients were confined to single, 1 min brain dialysate samples. After uptake inhibition with nomifensine (20 mg/kg i.p.), responses to electrical stimuli of 1 s duration were detected. [ABSTRACT FROM AUTHOR]

Emotional distracters impair cognitive function. Emotional processing is dysregulated in affective disorders such as depression, phobias, schizophrenia, and PTSD. Among the processes impaired by emotional distracters, and whose dysregulation is documented in affective disorders, is the ability to time in the seconds-to-minutes range, i.e. interval timing. Presentation of task-irrelevant distracters during a timing task results in a delay in responding suggesting a failure to maintain subjective time in working memory, possibly due to attentional and working memory resources being diverted away from timing, as proposed by the Relative Time-Sharing model. We investigated the role of the prelimbic cortex in the detrimental effect of anxiety-inducing task-irrelevant distracters on the cognitive ability to keep track of time, using local infusions of norepinephrine and dopamine reuptake inhibitor nomifensine in a modified peak-interval procedure with neutral and anxiety-inducing distracters. Given that some antidepressants have beneficial effects on attention and working memory, e.g., decreasing emotional response to negative events, we hypothesized that nomifensine would improve maintenance of information in working memory in trials with distracters, resulting in a decrease of the disruptive effect of emotional events on the timekeeping abilities. Our results revealed a dissociation of the effects of nomifensine infusion in prelimbic cortex between interval timing and resource allocation, and between neutral and anxiety-inducing distraction. Nomifensine was effective only during trials with distracters, but not during trials without distracters. Nomifensine reduced the detrimental effect of the distracters only when the distracters were anxiety-inducing, but not when they were neutral. Results are discussed in relation to the brain circuits involved in Relative Time-Sharing of resources, and the pharmacological management of affective disorders.

The dopamine ( DA) terminal fields in the rat dorsal striatum ( DS) and nucleus accumbens core ( NAcc) are organized as patchworks of domains that exhibit distinct kinetics of DA release and clearance. The present study used fast-scan cyclic voltammetry recordings of electrically evoked DA overflow to test the hypothesis that nomifensine might exhibit domain-dependent actions within the NAcc, as we previously found to be the case within the DS. Within the NAcc, nomifensine preferentially enhanced evoked DA overflow in the slow domains compared with the fast domains. To seek a kinetic explanation for nomifensine's selective actions, we quantified the apparent KM of DA clearance by numerically evaluating the derivative of the descending phase of the DA signal after the end of the stimulus. For comparison, we likewise quantified the apparent KM in the domains of the DS. As expected, because it is a competitive inhibitor, nomifensine significantly increased the apparent KM in both the fast and slow domains of both the NAcc and DS. However, our analysis also led to the novel finding that nomifensine preferentially increases the apparent KM in the NAcc compared with the DS; the apparent KM increased by ~500% in the NAcc and by ~200% in the DS. [ABSTRACT FROM AUTHOR]

Abstract: A motivational deficit (the loss of pleasure or interest in previously rewarding stimuli) is one of the core symptoms of major depression, and valid models evaluating the motivational effects of drugs are needed. It was recently demonstrated that the priming stimulation effect in the runway model of intracranial self-stimulation (ICSS) can be used as a model system to study the motivational effects of drugs. However, the characteristics of this novel experimental model have not been fully clarified. In this study, we investigated the effects of nomifensine and imipramine in the runway ICSS model, forced swim tests, and locomotor activity tests to differentiate motivation from affective-like states. Nomifensine dose-dependently increased running speed on the runway and decreased immobility time in the forced swim test. In contrast, imipramine decreased running speed on the runway although it also decreased immobility time in the forced swim test. In addition, the motivation-enhancing effect of nomifensine in the runway model was completely inhibited by pretreatment with the dopamine receptor antagonist haloperidol, although nomifensine-induced increases in locomotion were not affected by haloperidol. These results demonstrate that nomifensine displays motivation-enhancing and antidepressant-like effects. In addition, the motivational effects of nomifensine in the runway ICSS model are primarily mediated by dopamine receptors and enhancements of motivated behavior do not simply reflect hyperlocomotion. [Copyright &y& Elsevier]

Zebrafish ( Danio rerio ) are ideal model organisms for investigating nervous system function, both in health and disease. Nevertheless, functional characteristics of dopamine (DA) release and uptake regulation are still not well-understood in zebrafish. In this study, we assessed D3 autoreceptor function in the telencephalon of whole zebrafish brains ex vivo by measuring the electrically stimulated DA release ([DA] max ) and uptake at carbon fiber microelectrodes with fast-scan cyclic voltammetry. Treatment with pramipexole and 7-OH-DPAT, selective D3 autoreceptor agonists, sharply decreased [DA] max . Conversely, SB277011A, a selective D3 antagonist, nearly doubled [DA] max and decreased k , the first-order rate constant for the DA uptake, to about 20% of its original value. Treatment with desipramine, a selective norepinephrine transporter blocker, failed to increase current, suggesting that our electrochemical signal arises solely from the release of DA. Furthermore, blockage of DA uptake with nomifensine-reversed 7-OH-DPAT induced decreases in [DA] max . Collectively, our data show that, as in mammals, D3 autoreceptors regulate DA release, likely by inhibiting uptake. The results of this study are useful in the further development of zebrafish as a model organism for DA-related neurological disorders such as Parkinson's disease, schizophrenia, and drug addiction.

In the past two decades, ractopamine has been used as a feed additive to increase protein synthesis in farmed animals (swine, cattle, and turkeys) and to produce high-quality meat. However, the excessive feeding of animals with ractopamine may result in its accumulation in animal and human tissues after consuming the meat. Ractopamine is a trace amine-associated receptor1 and β-adrenoceptor agonist banned in the EU but approved in the USA, and it may pose a potential risk to human health. In this paper, the authors, for the first time, provide neurochemical evidence that ractopamine leads to the release of dopamine from nerve terminals of the nigrostriatal pathway in the striatum.

Breast cancer is one of the most challenging diseases to treat in humans worldwide. There are several alternatives in treating this life-threatening disease; however, chemoresistance is probably the biggest obstacle to the treatment of breast cancer. It may be essential to develop a therapeutic candidate material with less reversible effects and high treatment efficiency to solve this problem. The present study applied an ionizing radiation approach employing nomifensine (NF) to transform its chemical characteristics and investigated its potential to kill human breast cancer cells (MCF-7). Irradiated (IR-) NF was analyzed using high-performance liquid chromatography. The findings showed that NF inhibited the proliferation of breast cancer cells and increased the rate of apoptosis. In addition, IR-NF induced the accumulation of cytosolic reactive oxygen species and enhanced mitochondrial aggregation. Additionally, mitogen-activated protein kinases (extracellular signal-regulated kinase 1/2, p38 and c-Jun NH 2-terminal kinase) were involved in damage signaling induced by IR-NF and IR-NF suppressed β-catenin nuclear translocation. It is suggested that irradiation can be an effective method to maximize the efficacy of existing drugs and that IR-NF has the potential to be a drug candidate for treating patients with breast cancer. [ABSTRACT FROM AUTHOR]

Real-time investigations of neurotransmitter release provide a direct insight on the mechanisms involved in synaptic communication. Carbon fiber microelectrodes are state-of-the-art tools for electrochemical measurements of single vesicle neurotransmitter release. Yet, they lack high-throughput capabilities that are required for collecting robust statistically significant data across multiple samples. Here, we present a chip-based recording system enabling parallel in vitro measurements of individual neurotransmitter release events from cells, cultured directly on planar multielectrode arrays. The applicability of this cell-based platform to pharmacological screening is demonstrated by resolving minute concentration-dependent effects of the dopamine reuptake inhibitor nomifensine on recorded single-vesicle release events from PC12 cells. The experimental results, showing an increased half-time of the recorded events, are complemented by an analytical model for the verification of drug action. [ABSTRACT FROM AUTHOR]

Emotional distracters impair cognitive function. Emotional processing is dysregulated in affective disorders such as depression, phobias, schizophrenia, and post-traumatic stress disorder (PTSD). Among the processes impaired by emotional distracters, and whose dysregulation is documented in affective disorders, is the ability to time in the seconds-to-minutes range, i.e., interval timing. Presentation of task-irrelevant distracters during a timing task results in a delay in responding suggesting a failure to maintain subjective time in working memory, possibly due to attentional and working memory resources being diverted away from timing, as proposed by the Relative Time-Sharing (RTS) model. We investigated the role of the prelimbic cortex in the detrimental effect of anxiety-inducing task-irrelevant distracters on the cognitive ability to keep track of time, using local infusions of norepinephrine and dopamine reuptake inhibitor (NDRI) nomifensine in a modified peak-interval procedure with neutral and anxiety-inducing distracters. Given that some anti-depressants have beneficial effects on attention and working memory, e.g., decreasing emotional response to negative events, we hypothesized that nomifensine would improve maintenance of information in working memory in trials with distracters, resulting in a decrease of the disruptive effect of emotional events on the timekeeping abilities. Our results revealed a dissociation of the effects of nomifensine infusion in prelimbic cortex between interval timing and resource allocation, and between neutral and anxiety-inducing distraction. Nomifensine was effective only during trials with distracters, but not during trials without distracters. Nomifensine reduced the detrimental effect of the distracters only when the distracters were anxiety-inducing, but not when they were neutral. Results are discussed in relation to the brain circuits involved in RTS of resources, and the pharmacological management of affective disorders. [ABSTRACT FROM AUTHOR]

ABSTRACT This report is the first evidence of enantioselective binding of nomifensine to human serum albumin (HSA) and plasma proteins. The overall process with HSA included: (i) consistent experimental design along two independent sessions; (ii) incubation of nomifensine-HSA designed mixtures; (iii) ultrafiltration for separating the unbound enantiomers fraction; (iv) electrokinetic chromatography (EKC) using heptakis-2,3,6-tri- O-methyl- β-cyclodextrin as chiral selector to provide experimental data for enantiomers (first, E1, and second, E2, eluted ones); and (v) a recent direct equation allowing univariate tests and robust statistics to provide consistent parameters and uncertainty. A significant enantioselectivity to HSA (2.7 ± 0.1) was encountered, related to a 1:1 stoichiometry and log affinity constants of 3.24 ± 0.10 and 3.67 ± 0.08 for E1 and E2, respectively. The protein binding ( PB) estimated at physiological concentration levels was 40 ± 5 and 63 ± 4% for E1 and E2, respectively. The use of synthetic human sera allowed in vitro estimation of the total plasma PB for the racemate (61 ± 5%; coincident with in vivo values), and its enantiomers (58 ± 7 and 64 ± 4% for E1 and E2, respectively). Comparison allowed the relative importance of HSA respect to other plasma proteins for binding nomifensine to be established. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A chiral continuous bed was realized by a simple one-step synthesis and used to perform enantioseparations of drugs in nano-liquid chromatography (nano-LC). The capillary format of columns of this miniaturized technique allows to easily prepare in situ the chromatographic media. The continuous bed (also called monolithic) column was synthesized employing water-soluble comonomers and hydroxypropyl-β-cyclodextrin (HP-β-CD) was selected as a chiral selector. In order to make possible the one-step synthesis, HP-β-CD was previously activated as the allyl derivative. Several polymeric mixtures were studied to increase the enantiorecognition capability of the column. Analyses were carried out employing aqueous mobile phases, and the effect of organic modifiers and pH on enantiomeric resolution was studied. Among tested compounds, nomifensine and naproxen were baseline resolved, using a mobile phase containing respectively 20/80 methanol / water and 20/80 acetonitrile / water, both buffered with 0.1% triethylamine-acetate. A partial resolution was also achieved for praziquantel, metomidate and 5-methyl-5-phenyl-hydantoin. [ABSTRACT FROM AUTHOR]

Abstract: The insertion of microdialysis probes into the rat striatum disrupts dopaminergic activity near the probe track. The present study suggests that a substantial fraction of DA terminals near the probe track (200μm) survive the probe implantation itself but that the surviving terminals experience altered presynaptic inhibition. We found that probe implantation did not just alter the amplitude of evoked dopamine responses recorded by voltammetry, but also changed their temporal profile in a fashion similar to that previously observed by quinpirole, an agonist of dopamine D2 autoreceptors. Altered presynaptic inhibition is supported by a hypersensitivity of evoked dopamine responses recorded near to microdialysis probes to raclopride, a D2 antagonist. Further, we found that evoked dopamine release was also hypersensitive to a final dose of the dopamine transporter inhibitor, nomifensine. [Copyright &y& Elsevier]

Abstract: Nomifensine is a dopamine/norepinephrine reuptake inhibitor. Nomifensine and some of its structural analogues produce behavioral effects indicative of indirect dopaminergic agonist properties, such as hyperlocomotion. By contrast, the deaminated and demethylated nomifensine analogue 4-phenyl-1,2,3,4-tetrahydroisoquinoline (PTIQ) is reported to have amphetamine-antagonistic properties, as demonstrated by inhibition of methamphetamine (METH)-induced dopamine release in the nucleus accumbens and METH-induced hyperlocomotion in rats. In the present study, we examined the effect of PTIQ (10mg/kg, i.p.) and nomifensine (3mg/kg, i.p.) on METH (5 or 10mg/kg, i.p.)-induced stereotypical behavior in mice in order to determine whether PTIQ and nomifensine inhibit and augment, respectively, METH-induced stereotypical behavior. Unexpectedly, our observations demonstrated that both PTIQ and nomifensine significantly augmented METH-induced stereotypical behavior and locomotion in mice. This augmentation is likely the result of additive effects on dopaminergic function by METH in combination with PTIQ or nomifensine. These results suggest that, contrary to some reports, PTIQ may display dopaminergic agonist properties in mice. [Copyright &y& Elsevier]

Abstract: Strong positive correlation between depression and alcoholism is evident in epidemiological reports. However, a causal relationship for this co-morbidity has not been established. We have observed that chronic daily exposure to a relatively high dose of alcohol can induce depressive-like behavior in rats and that pretreatment with nomifensine or imipramine can block the “depressogenic” effects of alcohol. Since brain derived neurotrophic factor (BDNF) is considered to play an important role in depressive-like behaviors and its elevation, particularly in the hippocampus, appears to be critical for the action of many antidepressants, we hypothesized that: 1. WKY rats, a putative animal model of depression, will show a lower hippocampal BDNF compared to their control Wistar rats, 2. Alcohol-induced depressive like behavior will be associated with a significant decrease in hippocampal BDNF and 3. Treatments with antidepressants will normalize hippocampal BDNF. These postulates were verified by measuring hippocampal BDNF in Wistar and WKY rats at baseline, following chronic (10day) treatment with alcohol and combination of alcohol with nomifensine or imipramine. Alcohol was administered via inhalation chamber (3h/day) such that a blood alcohol level of approximately 150mg% was achieved. Nomifensine (10mg/kg) or imipramine (10mg/kg) was administered i.p. daily immediately after alcohol exposure. BDNF was measured by standard ELISA kit. The results support a role for central BDNF in depressogenic effects of alcohol and antidepressant effects of nomifensine and imipramine. Moreover, depression per se as manifested in WKY rats may be associated with a reduction in hippocampal BDNF. [Copyright &y& Elsevier]

Abstract: Extensive evidence suggests that the reinforcing effects of cocaine involve inhibition of dopamine transporters (DAT) and subsequent increases in dopamine (DA) levels in the striatum. We have previously reported that cocaine inhibits the DAT within 4–5 s of i.v. injection, matching the temporal profile of the behavioral and subjective effects of cocaine. Intravenous injection of GBR-12909, a high affinity, long-acting DAT inhibitor, also inhibits DA uptake within 5 s. Given that high affinity, long-acting drugs are considered to have relatively low abuse potential, we found it intriguing that GBR-12909 had an onset profile similar to that of cocaine. To further explore the onset kinetics of both low and high affinity DAT inhibitors, we examined the effects of i.v. cocaine (1.5 mg/kg), methylphenidate (1.5 mg/kg), nomifensine (1.5 mg/kg), GBR-12909 (1.5 mg/kg), PTT (0.5 mg/kg), and WF23 (0.5 mg/kg) on electrically-evoked DA release and uptake in the nucleus accumbens core. Results indicate that all of the DAT inhibitors significantly inhibited DA uptake within 5 s of injection. However, the timing of peak uptake inhibition varied greatly between the low and high affinity uptake inhibitors. Uptake inhibition following cocaine, methylphenidate, and nomifensine peaked 30 s following injection. In contrast, peak effects for GBR-12909, PTT, and WF23 occurred between 20 and 60 min following injection. These observations suggest that the initial onset for i.v. DAT inhibitors is extremely rapid and does not appear to be dictated by a drug''s affinity. [Copyright &y& Elsevier]

Abstract: Green odor is present in many green leaves, vegetables, and fruits and is composed of four 6-carbon straight-chain alcohols, n-hexanol, (E)-2-hexenol, (Z)-3-hexenol, and (E)-3-hexenol, and four aldehydes, n-hexanal, (E)-2-hexenal, (Z)-3-hexenal, and (E)-3-hexenal. It has been reported that certain green odor compounds enhance dopamine release from rat brain striatal slices and rat pheochromocytoma cells (PC12 cells). It is well known that intracellular Ca2+ levels regulate dopamine release. The amount of dopamine released by n-hexanal-treated PC12 cells decreased in cells pretreated with a membrane-permeable Ca2+ chelator. In this study, the effect of n-hexanal on dopamine release in the brain striatum of living rats was studied using an in vivo brain microdialysis system. Local stimulation with n-hexanal diluted in Ringer''s solution to 0.01%, 0.05%, or 0.1% enhanced dopamine release in a concentration-dependent manner. The amount of dopamine released with 0.01% n-hexanal administration significantly declined when either extracellular or intracellular Ca2+ levels decreased. Furthermore, the extracellular dopamine concentration increased with perfusion of nomifensine, an inhibitor of dopamine uptake into cells. When nomifensine was co-perfused with n-hexanal into the striatum, extracellular dopamine release increased further. Accordingly, the concentration of dopamine metabolite and the ratio of dopamine metabolite to dopamine decreased after treatment with n-hexanal. These responses were similar to those seen with KCl stimulation. These data suggest that n-hexanal stimulates dopamine release but does not inhibit dopamine uptake in the brain striatum of living rats, and that dopamine release associated with n-hexanal is regulated by both extracellular and intracellular Ca2+ levels. [Copyright &y& Elsevier]

Abstract: This study was undertaken to determine whether depression-like behavior can be observed in gonadally intact females that have experienced normal pregnancy. When tested on the forced swim test (FST) on postpartum days 1–7, previously pregnant rats spent slightly more time immobile, significantly less time swimming and diving, and defecated more than virgin controls. Subchronic treatment with nomifensine (DA reuptake inhibitor, 2.5mg/kg) but not sertraline (serotonin reuptake inhibitor, 10mg/kg) or desipramine (norepinephrine reuptake inhibitor, 10mg/kg) significantly decreased immobility on postpartum day 2. In rats pre-exposed to the FST in mid-pregnancy, neither subchronic nor chronic treatment with desipramine or sertraline decreased immobility on postpartum day 2; in contrast, chronic desipramine significantly decreased immobility in virgin controls. These results indicate that postpartum female rats, compared to virgin controls, show a reduction in some “active coping behaviors” but no significant increase in immobility when tested during the early postpartum period, unlike ovariectomized females that have undergone hormone-simulated pregnancy (HSP). Additionally, immobility that is increased by FST pre-exposure is not readily prevented by treatment with standard antidepressant medications in postpartum females. Depression-like behaviors previously observed in females that have undergone HSP may result from the more dramatic changes in estradiol, prolactin or corticosterone that occur during the early “postpartum” period, compared to the more subtle changes in these hormones that occur in actual postpartum females. [ABSTRACT FROM AUTHOR]

Abstract: Although strong positive association between alcoholism and depression is a common epidemiological observance, the causal relationship and the neurobiological substrates of such observations are far from clear. We have reported that chronic daily exposure to a relatively high dose of alcohol in rats can induce or exacerbate an already existing depressive-like behavior (Pharm Biochem Behav 91:97–103, 2008). Moreover, these effects of alcohol were blocked by pretreatment with desipramine, a tricyclic antidepressant, implicating a role for the biogenic amines in this type of depressive symptoms. In order to further delineate the involvement of specific neurotransmitters in alcohol-induced depressive symptoms, we examined the concentrations of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in the frontal cortex and hippocampus following alcohol administration as well as pretreatment with two antidepressants, nomifensine and imipramine selective NE/DA and NE/5-HT uptake inhibitors, respectively. Adult female Wistar and Wistar–Kyoto (WKY) rats were exposed to alcohol via inhalation chambers (3h/day for 10days) to achieve daily blood alcohol concentration of approximately 150mg%. On day 11, the animals were evaluated for general locomotor activity (LCA) and performance in the forced swim test (FST), followed by neurochemical analyses. As expected WKY rats had lower LCA and higher immobility in the FST compared to Wistar rats. WKY rats also had lower levels of all three biogenic amines compared to Wistar rats in both areas. However, only cortical NE was reduced in both strains following alcohol administration. Treatments with nomifensine and imipramine blocked the behavioral and most of the neurochemical deficits caused by alcohol in both strains. These results implicate cortical NE as a major player in alcohol-induced depression. Moreover, it is suggested that selective NE uptake inhibitors may be of particular therapeutic potential in co-morbid condition of alcoholism and depression. [Copyright &y& Elsevier]

The purpose of the present work was to assess the effects of glufosinate ammonium (GLA), an aminoacid structurally related to glutamate, on in vivo dopamine (DA) release from rat striatum, using brain microdialysis coupled to HPLC-EC. Intrastriatal administration of GLA produced significant concentration-dependent increases in DA levels. At least two mechanisms can be proposed to explain these increases: GLA could be inducing DA release from synaptic vesicles or producing an inhibition of DA transporter (DAT). Thus, we investigated the effects of GLA under Ca-free condition, and after pretreatment with reserpine and TTX. It was observed that the pretreatment with Ca-free Ringer, reserpine or TTX significantly reduced the DA release induced by GLA. Coinfusion of GLA and nomifensine shows that the GLA-induced DA release did not involve the DAT. These results show that GLA-induced striatal DA release is probably mediated by an exocytotic-, Ca-, action potential-dependent mechanism, being independent of DAT. [ABSTRACT FROM AUTHOR]

Abstract: Studies have demonstrated defects of DA and 5HT neurotransmission in dietary fat induced obese animals. In the present study, we used a perfusion system to assay the release of DA and 5HT from striatal slices preloaded with [3H]-DA or [3H]-5HT. The release of both DA and 5HT from striatal slices of rats fed a high fat diet for 10days, but not 3days, was reduced when compared to striatal slices taken from rats fed a low fat diet. Enterostatin, an endogenous pentapeptide inhibits dietary fat intake when administered peripherally and centrally in animals. The central mechanism for the action of enterostatin is not yet determined even though several mechanisms have been suggested. We have shown that enterostatin enhanced [3H]-DA release, but not [3H]-5HT release from striatal slices of rats that had been adapted to high fat diet for 10days. The enterostatin-induced increase in [3H]-DA release was blocked by nomifensine. Enterostatin did not alter [3H]-DA or [3H]-5HT release from striatal slices of rats adapted to high fat or low fat diet feeding for 3days. These findings suggest that enterostatin may inhibit dietary fat intake by blocking dopamine reuptake transport to increase central striatal DA release from rats that have acquired diminished dopamine signal after an adaptive period of fat consumption. [ABSTRACT FROM AUTHOR]

Nomifensine potently inhibits the reuptake of norepinephrine and dopamine in vitro. It is one of few antidepressants with marked potency to block dopamine reuptake that has ever been used clinically. Acute and sustained administration of nomifensine was investigated on the firing of monoaminergic neurons to understand its mechanism of action. In vivo extracellular recordings of locus coeruleus, ventral tegmental area and dorsal raphe nucleus neurons were obtained from male Sprague-Dawley rats. The intravenous injection of nomifensine in the locus coeruleus and ventral tegmental area yielded ED50 values of 40 ± 1 and 450 ± 41 µg/kg, respectively, suggesting that nomifensine directly acted upon dopamine and norepinephrine neurons, since these values are proportional to its affinities for norepinephrine and dopamine transporters. There was no effect on 5-HT neurons. Nomifensine (5 mg/kg/day, subcutaneous, using minipumps) potently and significantly inhibited dopamine neuronal firing in the ventral tegmental area after 2 days, with recovery to normal after the 14-day treatment due to D2 autoreceptor desensitization. Norepinephrine neuronal firing in the locus coeruleus was significantly decreased after 2 and 14 days. A significant increase in dorsal raphe nucleus 5-HT neuronal firing was seen after a two-day regimen, and remained elevated after 14 days. Desensitization of the 5-HT1A receptor on 5-HT neurons of the dorsal raphe nucleus occurred after two days of nomifensine administration. Nomifensine likely treated depression by acting on dopamine, norepinephrine and 5-HT neurons, highlighting the importance of the functional connectivity between these three monoaminergic systems. [ABSTRACT FROM AUTHOR]

Taking the antidepressant, nomifensine, this article focuses on the discovery and management of adverse drug reactions (ADRs) manifested in doctors' spontaneous post-marketing reports. Company-friendly experts, free-lancer research scientists, public servant physicians and regulatory scientists are shown to have made distinct contributions to ADR discovery. However, institutional and international fragmentation delayed synthesis of ADR reports into unambiguous discovery. Qualitative and quantitative interpretative standards of what counted as ADR discovery affected regulatory warning systems and decisions about when to withdraw a drug from the market. The timing and definition of an ADR as ‘irreversible’ or ‘rare’ was, in part, a function of the uncertainty and estimation criteria chosen by the party managing the discovery. UK regulators accepted relatively low levels of uncertainty, so the timing of discovery, warnings and regulatory action was relatively late, but US regulators chose higher thresholds of uncertainty about discovery when interpreting the need to warn of suspected serious ADRs. The implications of these practices for the founding ideals of a post-marketing ‘early warning system’ are considered. [ABSTRACT FROM PUBLISHER]

An efficient, general synthesis of 2-substituted thiazolo[4,5-f]isoquinolines, thiazolo[4,5-f]-quinolines and benzo[1,2-d:4,3-d']bisthiazoles has been accomplished from 5-nitroisoquinoline/quinoline and 6-nitrobenzothiazole, respectively, and all the products have been thoroughly identified spectroscopically (IR, 1H and 13C NMR, LR/ HR EI/ FAB/ ESI-MS). The synthesis of thiazolo[4,5-f]isoquinolines constitutes the first synthesis of this class of heteroarenes. Eighteen compounds, covering all three types, were screened for inhibition of COX-1 and COX-2, and some of them showed moderate activities. [ABSTRACT FROM AUTHOR]

The purpose of the present work was to assess the effects of flutriafol, a triazole fungicide, on in vivo dopamine (DA) release from rat striatum, using brain microdialysis coupled to high-performance liquid chromatography with electrochemical detection (HPLC¿EC). Intrastriatal administration of flutriafol (1, 6 and 12mM) produced significant concentration-dependent increases in DA levels to 218.5±51%, 1376±245% and 3093±345% compared with basal values, respectively. Those increases in DA levels could be due to an increased DA exocytotic release and/or a change in the activity of DA transporter (DAT). Thus, we investigated the effects of flutriafol (6mM) under Ca++- or Na+-free conditions, and after pretreatment with reserpine and TTX. When flutriafol was perfused in either Ca++- or Na+-free Ringer, the DA levels reduced 92% and 70%, respectively; perfusion of flutriafol in TTX-treated (10¿M) or reserpine-pretreated animals (10mg/kg), reduced the levels of DA to 73% and 86%, respectively. Co-infusion of flutriafol and nomifensine (20¿M) shows that the flutriafol-induced DA release did not involve the DAT. Our results suggest that flutriafol induces DA release via vesicular-, Ca++-, Na+- and TTX-dependent mechanism, being independent of DAT. [Copyright &y& Elsevier]

Abstract: Rotigotine is a new, non-ergoline dopamine receptor agonist developed for the treatment of Parkinson''s disease in a transdermal formulation (Neupro ®) to provide sustained drug delivery for 24 h with a once daily dosing. The aim of the present study was to determine whether or not continuous dopaminergic stimulation can interfere with the sleep–wake cycle. To achieve this, rotigotine was administered as a slow release formulation to provide stable plasma and brain levels over a period of 6 days and the sleep–wake cycle was evaluated in the freely-moving male rat using electroencephalagraphic recording. For comparison, the mixed dopamine/noradrenaline reuptake inhibitor nomifensine (16 mg/kg p.o.) was administered once daily for 6 days. In contrast to nomifensine, rotigotine (0.5 and 5 mg/kg s.c.) had no clear effects on the sleep–wake cycle. Nomifensine delayed the onset of rapid eye movement (REM) sleep and, to a lesser extent, also that of slow wave sleep (SWS). In addition, it increased the duration of waking time and decreased the duration of SWS and REM sleep. These effects were observed on all days and repeated administration lead neither to potentiation nor attenuation of the effects. It is concluded that a continuous dopaminergic stimulation of dopamine receptors by rotigotine may not only be beneficial for the treatment of the motor symptoms of Parkinson''s disease but also have additional benefits by not compromising either sleep architecture or circadian rhythm. [Copyright &y& Elsevier]

Abstract: 3-Nitropropionic acid (3-NP), an inhibitor of the mitochondrial enzyme succinate dehydrogenase, induces neuronal degeneration in the striatum. It is known that dopamine (DA) enhances this toxic effect. In this work, we study how the increase of DA influences the toxic effect of 3-NP on DAergic terminals, GABAergic neurons, astroglia and microglia in the striatum. We increased the content of DA through the inhibition of its uptake by nomifensine or the inhibition of its catabolism by deprenyl. We found that although nomifensine and deprenyl enhanced the DA overflow produced by 3-NP perfusion, they protected against the damage induced by 3-NP in the DAergic terminals and the GABAergic neurons in the striatum. Moreover, there was a decrease of apoptotic cells, astrogliosis and activation of microglia as index of damage. We also found that depletion of DA by reserpine and alpha-methyl-p-tyrosine produced a significant reduction of the inhibition of the respiratory rate and of the production of superoxide radical induced by 3-NP in synaptosomes from the striatum. All these results suggest that endogenous dopamine within the dopaminergic terminals of the striatum enhances the mitochondrial production of radical oxygen species along with the respiratory inhibition produced by 3-NP and thus increases the toxicity produced by 3-NP in the striatum. [Copyright &y& Elsevier]

Abstract: The present study was aimed to investigate the effects of a chronic treatment with the dopamine uptake blocker nomifensine on the in vivo extracellular concentrations of dopamine, acetylcholine, glutamate and GABA in the prefrontal cortex, striatum and nucleus accumbens. Male Wistar rats received intraperitoneal (i.p.) daily injections of nomifensine (10mg/kg) or saline for 22 days. Microdialysis experiments were performed on days 1, 8, 15 and 22 of treatment to evaluate the effects of the injection of nomifensine or saline. Motor activity of the animals was monitored during microdialysis experiments. Injections of nomifensine increased extracellular concentration of dopamine in striatum and nucleus accumbens, but not in prefrontal cortex. Acetylcholine concentrations in striatum but not in nucleus accumbens were increased by nomifensine on days 15 and 22 of treatment. In prefrontal cortex, nomifensine increased acetylcholine levels without differences among days. No changes were found on glutamate and GABA concentrations in the three areas studied. Injections of nomifensine also increased spontaneous motor activity and stereotyped behaviour without differences among days. These results show that systemic chronic treatment with a dopamine uptake blocker produces differential effects on extracellular concentrations of dopamine and acetylcholine, but not glutamate and GABA, in different areas of the brain. [Copyright &y& Elsevier]

Abstract: The in vivo effects of inorganic mercury (Hg2+) on striatal dopamine (DA) release were studied in freely moving and conscious rats using brain microdialysis techniques. Intrastriatal administration of HgCl2 (1mM) produced an increase in extracellular DA levels of 1717±375% with respect to basal levels. This effect was attenuated in a Ca2+-free medium (361±66%), after pre-treatment with reserpine (231±66%), and was prevented in the presence of tetrodotoxin (TTX). Thus, the HgCl2 treatment increases striatal DA according to an external calcium and vesicular dependent mechanism, being affected by the blockade of voltage sensitive sodium channels. Moreover, HgCl2 decreased KCl-evoked DA release. Conversely, the coinfusion of HgCl2 with nomifensine produced increases in DA extracellular levels different to that produced by nomifensine alone, suggesting that these effects probably involve an independent DA transporter (DAT) mechanism. [Copyright &y& Elsevier]