Cannabidiol Modulates the Motivational and Anxiety-Like Effects of 3,4-Methylenedioxypyrovalerone (MDPV) in Mice.

3,4-Methylenedioxypyrovalerone (MDPV) is a new psychoactive substance (NPS) and the most widespread and life-threatening synthetic cathinone of the "bath salts". Preclinical research has proven the cocaine-like psychostimulant effects of MDPV and its potential for abuse. Cannabidiol (CBD) is a non-psychotropic phytocannabinoid that has emerged as a new potential treatment for drug addiction. Here, we tested the effects of CBD (20 mg/kg) on MDPV (2 mg/kg)-induced conditioned place preference and MDPV (0.05 and 0.075 mg/kg/infusion) self-administration paradigms. In addition, we assessed the effects of the co-administration of CBD and MDPV (3 and 4 mg/kg) on anxiety-like behaviour using the elevated plus maze (EPM). CBD mitigated the MDPV-induced conditioned place preference. On the contrary, CBD administration throughout the MDPV (0.075 mg/kg/infusion) self-administration increased drug-seeking and taking behaviours, but only in the high-responders group of mice. Furthermore, CBD exerted anxiolytic-like effects, exclusively in MDPV-treated mice. Taken together, our results indicate that CBD modulation of MDPV-induced motivational responses in mice varies depending on the requirements of the learning task, resulting in a complex response. Therefore, further research attempting to decipher the behavioural and molecular interactions between CBD and MDPV is needed.

Hesperetin ameliorates electroconvulsive therapy-induced memory impairment through regulation of hippocampal BDNF and oxidative stress in a rat model of depression.

Depression is one of the most common mental health disorders and it is generally characterized by negative mood. Although electroconvulsive therapy (ECT) is an effective treatment for depression, however, it can cause cognitive deficit. Hesperetin, an active ingredient in citrus peels, has antioxidant and neuroprotective properties. In this study, we evaluated the effect of hesperetin on memory impairment induced by ECT in a reserpine-induced depression model in male rat. For this purpose, 105 male rats weighing 230-250 g were randomly divided into control and reserpine-treated groups. The reserpine-treated animals were subdivided into: Reserpine, Hesperetin (10 and 20 mg/kg), ECT and ECT+Hesperetin (10 and 20 mg/kg). After taking the drugs, the effect of hesperetin was evaluated through behavioral NORT, Y Maze, FST, SPT and also via assessment of hippocampal brain-derived neurotrophic factor (BDNF) and oxidative stress biomarkers i.e., MDA, SOD and GSH. As a result, our biochemical studies showed a significant decrease of MDA in groups treated with ECT+Hesperetin as compared to ECT and hesperetin groups (P < 0.001) and a marked increase in SOD, GSH and BDNF in ECT+Hesperetin 20 group as compared to other groups (p < 0.05). Also, the results of behavioral tests revealed that treatment with hesperetin can increase the novel object recognition index and alternation behaviors in Y maze test as compared to the groups treated with hesperetin or ECT (p < 0.05). These results suggest that co-administration of hesperetin with ECT is effective for improvement of cognitive function and can alleviate ECT-induced memory impairment in reserpine-treated rats.

Exposure to tricyclic antidepressant nortriptyline affects early-life stages of zebrafish (Danio rerio).

Psychiatric drugs are among the leading medications prescribed for humans, with their presence in aquatic environments raising concerns relating to potentially harmful effects on non-target organisms. Nortriptyline (NTP) is a selective serotonin-norepinephrine reuptake inhibitor antidepressant, widely used in clinics and found in environmental water matrices. In this study, we evaluated the toxic effects of NTP on zebrafish (Danio rerio) embryos and early larval stages. Developmental and mortality analyses were performed on zebrafish exposed to NTP for 168 h at concentrations ranging from 500 to 46,900 µg/L. Locomotor behaviour and acetylcholinesterase (AChE) activity were evaluated by exposing embryos/larvae to lower NTP concentrations (0.006-500 µg/L). The median lethal NTP concentration after 168 h exposure was 2190 µg/L. Although we did not identify significant developmental changes in the treated groups, lack of equilibrium was already visible in surviving larvae exposed to ≥ 500 µg/L NTP. The behavioural analyses showed that NTP was capable of modifying zebrafish larvae swimming behaviour, even at extremely low (0.006 and 0.088 µg/L) environmentally relevant concentrations. We consistently observed a significant reduction in AChE activity in the animals exposed to 500 µg/L NTP. Our results highlight acute toxic effects of NTP on the early-life stages of zebrafish. Most importantly, exposure to environmentally relevant NTP concentrations may affect zebrafish larvae locomotor behaviour, which in turn could reduce the fitness of the species. More studies involving chronic exposure and sensitive endpoints are warranted to better understand the effect of NTP in a more realistic exposure scenario.

Interaction of sigma-1 receptor modulators with seizure development in pentylenetetrazole-induced kindled mice.

This study aimed to investigate the effects of sigma receptor modulators, opipramol and BD-1063, on epileptogenesis in pentylenetetrazole (PTZ)-kindling model of epilepsy. Mice (n = 6/group) were received PTZ (30 mg/kg), PTZ plus opipramol (5 or 10 mg/kg), PTZ plus opipramol (5 mg/kg) plus BD-1063 (5 mg/kg, a selective sigma-1 receptor antagonist), and PTZ plus BD-1063 on alternate days for 15 days. Opipramol (5 and 10 mg/kg) + PTZ groups became fully kindled and had higher seizure scores compared to the PTZ group. In contrast, the PTZ plus BD-1063 and the PTZ plus opipramol (5 mg/kg) plus BD-1063 group did not show full kindling. These findings indicate that opipramol has a pro-convulsant effect, which is possibly mediated through activation of sigma-1 receptors.

Ameliorative effect of imperatorin in chemically induced fibromyalgia: Role of NMDA/NFkB mediated downstream signaling.

Fibromyalgia (FM) is a chronic pain syndrome involving complex interplay of biogenic amines and NMDA receptor mediated hypersensitization of nociceptive pathways. Clinical management of FM is poorly addressed with only a few available therapeutic options. Coumarins are active phenolic molecules of natural origin found to have broad pharmacological activities. Current investigation explores the role of naturally occurring coumarin, imperatorin in mouse model of fibromyalgia. Administration of reserpine (0.5 mg/kg, s.c.) thrice at 24 h intervals induced behavioral and neurochemical alterations characteristic of fibromyalgia. Reserpine was found to induce allodynia quantified using electronic von Frey (e-VF) and pressure application measurement (PAM) test, depression as indicated by an increased duration of immobility in forced swim test (FST), decreased motor coordination and locomotor activity in inclined plane test (IPT) and open field test (OFT) respectively. Cognitive deficits were evident by an increased latency to locate hidden platform in Morris water maze (MWM) and passive avoidance test (PAT). Reserpine treatment was found to cause an increased anxiety as revealed by increased time spent in closed arm of the elevated plus maze (EPM). Furthermore, an up- regulation in NMDA and NFκB expression in the brain and spinal cord was observed in reserpine treated groups. Administration of imperatorin (10 mg/kg, i.p) for a period of 5 days ameliorated all behavioral deficits, biochemical changes and decreased expression of NMDA and NFκB in the brain and spinal cord of treated mice. These findings indicate an interplay of NMDA/NFκB modulation by imperatorin in the reserpine induced fibromyalgia in mice.

Cardiovascular effects of 3,4-methylenedioxypyrovalerone (MDPV) in male and female Sprague-Dawley rats.

BACKGROUND: 3,4-methylenedioxypyrovalerone (MDPV) toxicity includes intense neurological and cardiovascular events. We examined MDPV-induced cardiovascular, temperature, and locomotor effects following escalating and repeated MDPV administration in adult male and female Sprague-Dawley rats and compared these effects to cocaine in male rats. METHODS: Telemetry devices were surgically implanted to allow continuous measurement of cardiovascular, temperature, and locomotor activity over a 22 h period after dosing. Rats were administered increasing intraperitoneal (IP) MDPV doses (1-5.6 mg/kg) every other day, followed two days later by a binge regimen of four injections of 3 mg/kg MDPV at 2 h intervals. MDPV serum concentrations were measured by LC-MS/MS. Cocaine (3-30 mg/kg) and four injections of 30 mg/kg IP were administered to male rats for comparison with male MDPV data. RESULTS: The duration of MDPV cardiovascular effects was significantly greater (p < 0.05) in male rats than female rats at 3-5.6 mg/kg. The ED50 for MDPV-induced locomotor was significantly lower in males (2.4 ± 0.3) than females (3.4 ± 0.2). Males showed significantly greater variability in MDPV serum concentrations than females after binge dosing. MDPV produced five-fold more potent cardiovascular effects than cocaine in male rats. MDPV did not alter thermoregulation in either sex, but cocaine binge administration decreased temperature. CONCLUSION: Effects of MDPV on temperature were not significantly different between sexes. MDPV-induced cardiovascular and locomotor effects in males lasted significantly longer and were more potent than in females. These differences appeared to be related to pharmacokinetic factors leading to greater variance in MDPV serum concentrations in males.

Serotonergic dysfunction in a model of parkinsonism induced by reserpine.

Parkinson's disease (PD) is mainly characterized by a dopamine deficiency accompanied by structural and functional changes in striatal neuronal projections. However, studies have considered PD as a multi-systemic disease in which the neurodegenerative process extends beyond the dopaminergic system. Therefore, the purpose of the present study was to investigate the time-course of serotonergic neuron damage in a progressive model of parkinsonism induced by a low dose of reserpine. Thus, male Wistar rats received 4 (ST, short-treatment of reserpine) or 10 (MT, middle-term treatment of reserpine) subcutaneous injections of vehicle or reserpine (0.1 mg/kg) at a volume of 1 mL/kg body weight, on alternate days. Animals were euthanized 48 h after the last injection for immunohistochemical analysis. After ST, 5-HT immunoreactivity decreased in hippocampal subareas (CA1 and CA3) and medial prefrontal cortex (mPFC) compared to vehicle. Furthermore, animals MT-treated also showed progressive decrease of 5-HT immunoreactivity in CA1 and CA3 subareas. Conversely, a significant increase of 5-HT immunoreactivity was found in mPFC and dorsal raphe nucleus (DRN) in animals submitted to MT when compared to ST exposure. The results showed that, in the repeated low-dose reserpine rat model, variations in the immunoreactivity of 5-HT start early in the course of progressive parkinsonism.

Reversal of reserpine-induced depression and cognitive disorder in zebrafish by sertraline and Traditional Chinese Medicine (TCM).

BACKGROUND: With increased social pressure, individuals face a high risk of depression. Subsequently, depression affects cognitive behaviour and negatively impacts daily life. Fortunately, the Traditional Chinese Medicine Jia Wei Xiao Yao (JWXY) capsule is effective in reducing depression and improving cognitive behaviour. METHODS: The constituents of JWXY capsule were identified by ultra-performance liquid chromatography and quadrupole time-of-flight mass spectrometry analyses. We analysed behaviours of depression-like zebrafish in the novel tank with an automatic 3D video-tracking system and conducted the colour preference test, as well detected physiological changes after sertraline and JWXY capsule treatments. RESULTS: Both sertraline and JWXY capsule rescued the decreased locomotive behaviour and depression phenotype of zebrafish caused by reserpine. JWXY capsule especially improved the inhibited exploratory behaviour caused by reserpine. In addition, with the onset of depressive behaviour, zebrafish exhibited alterations in cognitive behaviour as indicated by colour preference changes. However, compared with sertraline, JWXY capsule was more efficaciously in rescuing this change in the colour preference pattern. Moreover, an increased level of cortisol, increased expression of tyrosine hydroxylase (TH) and decreased monoamine neurotransmitters, including serotonin (5-HT) and noradrenaline, were involved in the depressive behaviours. In addition, sertraline and JWXY capsule rescued the depressive phenotype and cognitive behaviour of zebrafish by altering the levels of endogenous cortisol and monoamine neurotransmitters. CONCLUSIONS: JWXY capsule was more effectively than sertraline in rescuing reserpine-induced depression and cognitive disorder in zebrafish. Potentially, our study can provide new insights into the clinical treatment of depression and the mechanism of action of JWXY capsule.

No major role of norepinephrine transporter gene variations in the cardiostimulant effects of MDMA.

PURPOSE: Methylenedioxymethamphetamine (MDMA, ecstasy) is used recreationally and frequently leads to sympathomimetic toxicity. MDMA produces cardiovascular and subjective stimulant effects that were shown to partially depend on the norepinephrine transporter (NET)-mediated release of norepinephrine and stimulation of α1-adrenergic receptors. Genetic variants, such as single-nucleotide polymorphisms (SNPs), of the NET gene (SLC6A2) may explain interindividual differences in the acute stimulant-type responses to MDMA in humans. METHODS: We characterized the effects of common genetic variants of the SLC6A2 gene (rs168924, rs47958, rs1861647, rs2242446, and rs36029) on cardiovascular and subjective stimulation after MDMA administration in 124 healthy subjects in a pooled analysis of eight double-blind, placebo-controlled studies. RESULTS: Carriers of the GG genotype of the SLC6A2 rs1861647 SNP presented higher elevations of heart rate and rate-pressure product after MDMA than subjects with one or no G alleles. Subjects with a C allele in the SLC6A2 rs2242446 SNP presented higher elevations of the heart rate after MDMA administration compared with the TT genotype. Subjects with the AA genotype of the SLC6A2 rs36029 SNP presented higher elevations of mean arterial pressure and rate pressure product after MDMA administration than carriers of the G allele. The SLC6A2 rs168924 and rs47958 SNPs did not alter the response to MDMA. CONCLUSIONS: Genetic polymorphisms of the SLC6A2 gene weakly moderated the acute cardiovascular response to MDMA in controlled studies and may play a minor role in adverse cardiovascular events when MDMA is used recreationally.

Prenatal nicotine exposure decreases the release of dopamine in the medial frontal cortex and induces atomoxetine-responsive neurobehavioral deficits in mice.

Increased risk of attention-deficit/hyperactivity disorder (AD/HD) is partly associated with the early developmental exposure to nicotine in tobacco smoke. Emerging reports link tobacco smoke exposure or prenatal nicotine exposure (PNE) with AD/HD-like behaviors in rodent models. We have previously reported that PNE induces cognitive behavioral deficits in offspring and decreases the contents of dopamine (DA) and its turnover in the prefrontal cortex (PFC) of offspring It is well known that the dysfunction of DAergic system in the brain is one of the core factors in the pathophysiology of AD/HD. Therefore, we examined whether the effects of PNE on the DAergic system underlie the AD/HD-related behavioral changes in mouse offspring. PNE reduced the release of DA in the medial PFC (mPFC) in mouse offspring. PNE reduced the number of tyrosine hydroxylase (TH)-positive varicosities in the mPFC and in the core as well as the shell of nucleus accumbens, but not in the striatum. PNE also induced behavioral deficits in cliff avoidance, object-based attention, and sensorimotor gating in offspring. These behavioral deficits were attenuated by acute treatment with atomoxetine (3 mg/kg, s.c.) or partially attenuated by acute treatment with MPH (1 mg/kg, s.c.). Taken together, our findings support the notion that PNE induces neurobehavioral abnormalities in mouse offspring by disrupting the DAergic system and improve our understanding about the incidence of AD/HD in children whose mothers were exposed to nicotine during their pregnancy.

Tph2 gene deletion enhances amphetamine-induced hypermotility: effect of 5-HT restoration and role of striatal noradrenaline release.

Variants of tryptophan hydroxylase-2 (Tph2), the gene encoding enzyme responsible for the synthesis of brain serotonin (5-HT), have been associated with neuropsychiatric disorders, substance abuse and addiction. This study assessed the effect of Tph2 gene deletion on motor behavior and found that motor activity induced by 2.5 and 5 mg/kg amphetamine was enhanced in Tph2(-/-) mice. Using the in vivo microdialysis technique we found that the ability of amphetamine to stimulate noradrenaline (NA) release in the striatum was reduced by about 50% in Tph2(-/-) mice while the release of dopamine (DA) was not affected. Tph2 deletion did not affect the release of NA and DA in the prefrontal cortex. The role of endogenous 5-HT in enhancing the effect of amphetamine was confirmed showing that treatment with the 5-HT precursor 5-hydroxytryptophan (10 mg/kg) restored tissue and extracellular levels of brain 5-HT and the effects of amphetamine on striatal NA release and motor activity in Tph2(-/-) mice. Treatment with the NA precursor dihydroxyphenylserine (400 mg/kg) was sufficient to restore the effect of amphetamine on striatal NA release and motor activity in Tph2(-/-) mice. These findings indicate that amphetamine-induced hyperactivity is attenuated by endogenous 5-HT through the inhibition of striatal NA release. Tph2(-/-) mice may be a useful preclinical model to assess the role of 5-HT-dependent mechanisms in the action of psychostimulants. Acute sensitivity to the motor effects of amphetamine has been associated to increased risk of psychostimulant abuse. Here, we show that deletion of Tph2, the gene responsible for brain 5-HT synthesis, enhances the motor effect of amphetamine in mice through the inhibition of striatal NA release. This suggests that Tph2(-/-) mice is a useful preclinical model to assess the role of 5-HT-dependent mechanisms in psychostimulants action. Tph2, tryptophan hydroxylase-2.

Depressive-like symptoms in a reserpine-induced model of fibromyalgia in rats.

Since the pathogenesis of fibromyalgia is unknown, treatment options are limited, ineffective and in fact based on symptom relief. A recently proposed rat model of fibromyalgia is based on central depletion of monamines caused by reserpine administration. This model showed widespread musculoskeletal pain and depressive-like symptoms, but the methodology used to measure such symptoms has been criticized. Evidence relates the high prevalence of pain and depression in fibromyalgia to common pathogenic pathways, most probably focused on the monoaminergic system. The present study aims at a validation of the reserpine model of fibromyalgia. For this purpose, rats undergoing this model have been tested for depressive-like symptoms with a Novelty-Suppressed Feeding Test adaptation. Animals administered with reserpine and subjected to forced food deprivation performed a smaller number of incursions to the center of the open field, evidenced by a decrease in the per-minute rate of the rats' approaching, smelling or touching the food. They also took more time to eat from the central food than control rats. These NSFT findings suggest the presence of depressive-like disorders in this animal model of fibromyalgia.

Adenosine signaling in reserpine-induced depression in rats.

A single, 6 mg/kg intraperitoneal injection of reserpine increased floating time during forced swim testing 24h after administration in rats in five experiments. Although such behavioral depression traditionally is attributed to drug-induced depletion of brain monoamines, we examined the potential contribution of adenosine signaling, which is plausibly activated by reserpine treatment and contributes to behavioral depression in other paradigms. Whereas peripheral administration of the highly selective A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (0.5, 1.0, or 5.0mg/kg i.p.) 15 min before swim testing failed to improve performance in reserpine-treated rats, swim deficits were completely reversed by 7 mg/kg of the nonselective receptor antagonist caffeine. Performance deficits were also reversed by the nonselective A2 antagonist 3,7-dimethylxanthine (0, 0.5, 1.0mg/kg i.p.), and the highly selective A2A receptor antagonist (CSC: 8-(3 chlorostyral)caffeine) (0.01, 0.1, or 1.0mg/kg i.p.) in a dose-dependent manner. The highly selective A2B antagonist alloxazine had no beneficial effect on swim performance at any dose under study (0.1, 1.0, and 5.0mg/kg i.p.).

MPTP-induced dopamine neuron degeneration and glia activation is potentiated in MDMA-pretreated mice.

Clinical observations report a greater propensity to develop Parkinson's disease (PD) in amphetamine users. 3,4-Methylenedioxymethamphetamine (MDMA; "ecstasy") is an amphetamine-related drug that is largely consumed by adolescents and young adults, which may have neuroinflammatory and neurotoxic effects. Here, the objective was to evaluate in mice whether consumption of MDMA during adolescence might influence the neuroinflammatory and neurotoxic effects of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a toxin known to induce PD in humans. The activation of astroglia and microglia by glial fibrillary acidic protein (GFAP) and complement receptor type 3 (CD11b) immunohistochemistry and the degeneration of dopaminergic neurons by tyrosine hydroxylase (TH) immunohistochemistry were evaluated. MPTP (20 mg/kg × 4) was administered to mice treated from ages 8 weeks to 17 weeks with MDMA (10 mg/kg twice daily, two times a week). In mice that were chronically treated with MDMA, administration of MPTP induced a higher microglial and astroglial response in both the striatum and the substantia nigra pars compacta (SNc) compared with vehicle-treated or vehicle + MPTP-treated mice. Inflammatory changes were associated with a decrease in TH immunoreactivity in the SNc of MDMA-treated mice and with a further decrease in the striatum and the SNc of MDMA + MPTP-treated mice compared with vehicle-treated, MDMA-treated, and MPTP-treated mice. The results demonstrate that chronic administration of MDMA during late adolescence in mice exacerbates the neurodegeneration and neuroinflammation caused by MPTP, suggesting that MDMA may constitute a risk factor for dopaminergic neuron degeneration.

Desvenlafaxine succinate ameliorates visceral hypersensitivity but delays solid gastric emptying in rats.

Desvenlafaxine succinate (DVS) is a novel serotonin and norepinephrine reuptake inhibitor. The aim of this study was to investigate the effects of DVS on visceral hypersensitivity and solid gastric emptying in a rodent model of gastric hyperalgesia. Twenty-eight gastric hyperalgesia rats and 20 control rats were used. Visceral sensitivity during gastric distention (GD) was assessed by recording of electromyogram (EMG) at pressures of 20, 40, 60, and 80 mmHg. DVS with doses of 1, 10, and 30 mg/kg were administrated by gavage, 5-HT1A antagonist (WAY-100635, 0.3 mg/kg) was given subcutaneously, and 5-HT2A antagonist (ketanserin, 1 mg/kg) was given intraperitoneally. The level of norepinephrine in plasma was measured by enzyme-linked immunosorbent assay. We found that 1) visceral hypersensitivity induced by acetic acid was validated. 2) DVS dose-dependently reduced visceral hypersensitivity in the gastric hypersensitivity rats. The EMG (% of baseline value without GD) during GD at 60 and 80 mmHg with DVS at a dose of 30 mg/kg were 119.4 ± 2.3% (vs. saline 150.9 ± 2.7%, P < 0.001) and 128.2 ± 3.2% (vs. saline 171.1 ± 2.4%, P < 0.001). Similar findings were observed at a dose of 10 mg/kg. DVS at a dose of 1 mg/kg reduced visceral hypersensitivity only during GD at 60 mmHg. 3) Neither WAY-100635 nor ketanserin blocked the effect of DVS on visceral sensitivity. 4) DVS at 30 mg/kg significantly increased plasma NE level (P = 0.012 vs. saline). 5) DVS at 30 mg/kg significantly delayed solid gastric emptying (P < 0.05 vs. saline). We conclude that DVS reduces visceral sensitivity in a rodent model of visceral hypersensitivity and delays solid gastric emptying. Caution should be made when DVS is used for treating patients.

Gallic acid decreases vacuous chewing movements induced by reserpine in rats.

Involuntary oral movements are present in several diseases and pharmacological conditions; however, their etiology and efficient treatments remain unclear. Gallic acid is a natural polyphenolic acid found in gall nuts, sumac, oak bark, tea leaves, grapes and wine, with potent antioxidant and antiapoptotic activity. Thus, the present study investigated the effects of gallic acid on vacuous chewing movements (VCMs) in an animal model induced by reserpine. Rats received either vehicle or reserpine (1mg/kg/day, s.c.) during three days, followed by treatment with water or different doses of gallic acid (4.5, 13.5 or 40.5mg/kg/day, p.o.) for three more days. As result, reserpine increased the number of VCMs in rats, and this effect was maintained for at least three days after its withdrawal. Gallic acid at two different doses (13.5 and 40.5mg/kg/day) has reduced VCMs in rats previously treated with reserpine. Furthermore, we investigated oxidative stress parameters (DCFH-DA oxidation, TBARS and thiol levels) and Na(+),K(+)-ATPase activity in striatum and cerebral cortex, however, no changes were observed. These findings show that gallic acid may have promissory use in the treatment of involuntary oral movements.

Effects of repeated treatment with MDMA on working memory and behavioural flexibility in mice.

Repeated administration of 3,4-methylenedioxymethamphetamine (MDMA) produces dopaminergic neurotoxicity in mice. However, it is still not clear whether this exposure induces deficits in cognitive processing related to specific subsets of executive functioning. We evaluated the effects of neurotoxic and non-neurotoxic doses of MDMA (0, 3 and 30 mg/kg, twice daily for 4 days) on working memory and attentional set-shifting in mice, and changes in extracellular levels of dopamine (DA) in the striatum. Treatment with MDMA (30 mg/kg) disrupted performance of acquired operant alternation, and this impairment was still apparent 5 days after the last drug administration. Decreased alternation was not related to anhedonia because no differences were observed between groups in the saccharin preference test under similar experimental conditions. Correct responding on delayed alternation was increased 1 day after repeated treatment with MDMA (30 mg/kg), probably because of general behavioural quiescence. Notably, the high dose regimen of MDMA impaired attentional set-shifting related to an increase in total perseveration errors. Finally, basal extracellular levels of DA in the striatum were not modified in mice repeatedly treated with MDMA with respect to controls. However, an acute challenge with MDMA (10 mg/kg) failed to increase DA outflow in mice receiving the highest MDMA dose (30 mg/kg), corroborating a decrease in the functionality of DA transporters. Seven days after this treatment, the effects of MDMA on DA outflow were recovered. These results suggest that repeated neurotoxic doses of MDMA produce lasting impairments in recall of alternation behaviour and reduce cognitive flexibility in mice.

The effect of adenosine A(2A) receptor antagonists on hydroxyl radical, dopamine, and glutamate in the striatum of rats with altered function of VMAT2.

It has been shown that a decreased vesicular monoamine transporter (VMAT2) function and the disruption of dopamine (DA) storage is an early contributor to oxidative damage of dopamine neurons in Parkinson's disease (PD). In our previous study, we demonstrated that adenosine A(2A) receptor antagonists suppressed oxidative stress in 6-hydroxydopamine-treated rats suggesting that this effect may account for neuroprotective properties of drugs. In the present study, rats were injected with reserpine (10 mg/kg sc) and 18 h later the effect of the adenosine A(2A) receptor antagonists 8-(3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on extracellular DA, glutamate and hydroxyl radical formation was studied in the rat striatum using in vivo microdialysis. By disrupting VMAT2 function, reserpine depleted DA stores, and increased glutamate and hydroxyl radical levels in the rat striatum. CSC (1 mg/kg) but not ZM 241385 (3 mg/kg) increased extracellular DA level and production of hydroxyl radical in reserpinised rats. Both antagonists decreased the reserpine-induced increase in extracellular glutamate. L-3,4-Dihydroxyphenylalanine (L-DOPA) (25 mg/kg) significantly enhanced extracellular DA, had no effect on reserpine-induced hydroxyl radical production and decreased extracellular glutamate concentration. CSC but not ZM 241385 given jointly with L-DOPA increased the effect of L-DOPA on extracellular DA and augmented the reserpine-induced hydroxyl radical production. CSC and ZM 241385 did not influence extracellular glutamate level, which was decreased by L-DOPA. It seems that by decreasing the MAO-dependent DA metabolism rate, CSC raised cytosolic DA and by DA autoxidation, it induced hydroxyl radical overproduction. Thus, the methylxanthine A(2A) receptor antagonists bearing properties of MAO-B inhibitor, like CSC, may cause a risk of oxidative stress resulting from dysfunctional DA storage mechanism in early PD.

Prenatal exposure to MDMA alters noradrenergic neurodevelopment in the rat.

3,4-methylenedioxymethamphetamine (MDMA; ecstasy) binds with high affinity to the norepinephrine transporter (NET), making the noradrenergic system a potential target during fetal exposure. Recent data indicate that adult rats that had been prenatally exposed to MDMA display persistent deficits in working memory and attention; behaviors consistent with abnormal noradrenergic signaling in the forebrain. The present study was designed to investigate whether prenatal exposure to MDMA from embryonic days 14-20 affects the structure and/or function of the noradrenergic system of the rat on postnatal day 21. Offspring that were prenatally exposed to MDMA exhibited an increase in noradrenergic fiber density in the prelimbic region of the prefrontal cortex and the CA1 region of the hippocampus that was not accompanied by an increase in the number of noradrenergic neurons in the locus coeruleus. Direct tissue autoradiography using tritiated nisoxetine demonstrated that while NET binding was not altered in the prelimbic cortex, the dentate gyrus, or the locus coeruleus, it was increased in the CA1, CA2, and CA3 regions of the hippocampus. Basal levels of norepinephrine were increased in the prefrontal cortex and the nucleus accumbens of MDMA-exposed rats, as compared to saline-treated controls. These findings indicate that prenatal exposure to MDMA results in structural changes in the noradrenergic system as well as functional alterations in NE neurotransmission in structures that are critical in attentional processing.

Nrf2 deficiency potentiates methamphetamine-induced dopaminergic axonal damage and gliosis in the striatum.

Oxidative stress that correlates with damage to nigrostriatal dopaminergic neurons and reactive gliosis in the basal ganglia is a hallmark of methamphetamine (METH) toxicity. In this study, we analyzed the protective role of the transcription factor Nrf2 (nuclear factor-erythroid 2-related factor 2), a master regulator of redox homeostasis, in METH-induced neurotoxicity. We found that Nrf2 deficiency exacerbated METH-induced damage to dopamine neurons, shown by an increase in loss of tyrosine hydroxylase (TH)- and dopamine transporter (DAT)-containing fibers in striatum. Consistent with these effects, Nrf2 deficiency potentiated glial activation, indicated by increased striatal expression of markers for microglia (Mac-1 and Iba-1) and astroglia (GFAP) one day after METH administration. At the same time, Nrf2 inactivation dramatically potentiated the increase in TNFα mRNA and IL-15 protein expression in GFAP+ cells in the striatum. In sharp contrast to the potentiation of striatal damage, Nrf2 deficiency did not affect METH-induced dopaminergic neuron death or expression of glial markers or proinflammatory molecules in the substantia nigra. This study uncovers a new role for Nrf2 in protection against METH-induced inflammatory and oxidative stress and striatal degeneration.