The neuroprotective effect of exogen melatonin upon fetal hippocampus damage caused by high-dose caffeine administration in pregnant rats.

OBJECTIVE: The aim of this study is to evaluate whether exogenous melatonin (MEL) mitigates the deleterious effects of high-dose caffeine (CAF) administration in pregnant rats upon the fetal hippocampus. MATERIALS AND METHODS: A total of 32 adult Wistar albino female rats were divided into four groups after conception (n = 8). At 9-20 days of pregnancy, intraperitoneal (i.p.) MEL was administered at a dose of 10 mg/kg/day in the MEL group, while i.p. CAF was administered at a dose of 60 mg/kg/day in the CAF group. In the CAF plus MEL group, i.p. CAF and MEL were administered at a dose of 60 and 10 mg/kg/day, respectively, at the same period. Following extraction of the brains of the fetuses sacrificed on the 21st day of pregnancy, their hippocampal regions were analyzed by hematoxylin and eosin and Cresyl Echt Violet, anti-GFAP, and antisynaptophysin staining methods. RESULTS: While there was a decrease in fetal and brain weights in the CAF group, it was found that the CAF plus MEL group had a closer weight average to that of the control group. Histologically, it was observed that the pyramidal cell layer consisted of 8-10 layers of cells due to the delay in migration in hippocampal neurons in the CAF group, while the MEL group showed similar characteristics with the control group. It was found that these findings decreased in the CAF plus MEL group. CONCLUSION: It is concluded that high-dose CAF administration causes a delay in neurogenesis of the fetal hippocampus, and exogenous MEL is able to mitigate its deleterious effects.

Melatonin enhances the restoration of neurological impairments and cognitive deficits during drug withdrawal in methamphetamine-induced toxicity and endoplasmic reticulum stress in rats.

Methamphetamine (METH) is a psychostimulant with a very high addiction rate. Prolonged use of METH has been observed as one of the root causes of neurotoxicity. Melatonin (Mel) has been found to have a significant role in METH-induced neurotoxicity. This study aimed to investigate the restorative effect of Mel on behavioral flexibility in METH-induced cognitive deficits. Male Sprague-Dawley rats were randomly assigned to be intraperitoneally injected with saline (control) or Meth at 5 mg/kg for 7 consecutive days. Then, METH injection was withdrawn and rats in each group were subcutaneously injected with saline or Mel at 10 mg/kg for 14 consecutive days. The stereotypic behavioral test and attentional set-shifting task (ASST) were used to evaluate neurological functions and cognitive flexibility, respectively. Rats developed abnormal features of stereotyped behaviors and deficits in cognitive flexibility after 7 days of METH administration. However, post-treatment with Mel for 14 days after METH withdrawal dramatically ameliorated the neurological and cognitive deficits in METH-treated rats. Blood biomarkers indicated METH-induced systemic low-grade inflammation. Moreover, METH-induced endoplasmic reticulum (ER) stress in the prefrontal cortex was diminished by melatonin supplementation. These findings might reveal the therapeutic potential of Mel in METH toxicity-induced neurological and cognitive deficits.

Parkin-deficient rats are resistant to neurotoxicity of chronic high-dose methamphetamine.

Methamphetamine (METH) is a highly addictive and powerful central nervous system psychostimulant with no FDA-approved pharmacotherapy. Parkin is a neuroprotective protein and its loss of function contributes to Parkinson's disease. This study used 3-month-old homozygous parkin knockout (PKO) rats to determine whether loss of parkin protein potentiates neurotoxicity of chronic METH to the nigrostriatal dopamine pathway. PKO rats were chronically treated with 10 mg/kg METH for 10 consecutive days and assessed for neurotoxicity markers in the striatum on the 5th and 10th day of withdrawal from METH. The PKO rats showed higher METH-induced hyperthermia; however, they did not display augmented deficits in dopaminergic and serotonergic neurotoxicity markers, astrocyte activation or decreased mitochondrial enzyme levels as compared to wild-type (WT) rats. Interestingly, saline-treated PKO rats had lower levels of dopamine (DA) as well as mitochondrial complex I and II levels while having increased basal levels of glial fibrillary acidic protein (GFAP), a marker of gliosis. These results indicate PKO display a certain resistance to METH neurotoxicity, possibly mediated by lowered DA levels and downregulated mitochondria.

Stimulants cocktail: Methylphenidate plus caffeine impairs memory and cognition and alters mitochondrial and oxidative status.

Methylphenidate (MPH) is a psychostimulant widely misused to increase wakefulness by drivers and students. Also, MPH can be found in dietary supplements in a clandestine manner aiming to burst performance of physical exercise practitioners. The abusive use of high doses of caffeine (CAF) in these contexts is equally already known. Here, we demonstrate the behavioral, oxidative and mitochondrial effects after acute exposure to high doses of MPH (80 mg/L) and CAF (150 mg/L), alone or associated (80 mg/L + 150 mg/L, respectively). We used zebrafish as animal model due to its high translational relevance. We evaluated the behavioral effects using the Novel Tank Test (NTT), Social Preference Test (SPT) and Y-maze Task and analyzed biomarkers of oxidative stress and activity of mitochondrial respiratory chain complexes. MPH alone induced antisocial behavior. MPH inhibited lipid peroxidation. The association of MPH + CAF presented memory impairment and anxiogenic behavior. In oxidative status, it inhibited lipid peroxidation, increased protein carbonylation and mitochondrial complex II, III and IV activity. Our results demonstrate that MPH and CAF alone negatively impact the typical behavioral of zebrafish. When associated, changes in cognition, memory, oxidative and mitochondrial status are more relevant.

High ambient temperature increases the toxicity and lethality of 3,4-methylenedioxymethamphetamine and methcathinone.

RATIONALE: Methylenedioxymethamphetamine (MDMA) and methcathinone (MCAT) are abused psychostimulant drugs that produce adverse effects in human users that include hepatotoxicity and death. Recent work has suggested a connection between hepatotoxicity, elevations in plasma ammonia, and brain glutamate function for methamphetamine (METH)-induced neurotoxicity. OBJECTIVES: These experiments investigated the effect of ambient temperature on the toxicity and lethality produced by MDMA and MCAT in mice, and whether these effects might involve similar mechanisms to those described for METH neurotoxicity. RESULTS: Under low (room temperature) ambient temperature conditions, MDMA induced hepatotoxicity, elevated plasma ammonia levels, and induced lethality. Under the same conditions, even a very high dose of MCAT produced limited toxic or lethal effects. High ambient temperature conditions potentiated the toxic and lethal effects of both MDMA and MCAT. CONCLUSION: These studies suggest that hepatotoxicity, plasma ammonia, and brain glutamate function are involved in MDMA-induced lethality, as has been shown for METH neurotoxicity. The toxicity and lethality of both MDMA and MCAT were potentiated by high ambient temperatures. Although an initial mouse study reported that several cathinones were much less toxic than METH or MDMA, the present results suggest that it will be essential to assess the potential dangers posed by these drugs under high ambient temperatures.

Epigallocatechin Gallate Mitigates the Methamphetamine-Induced Striatal Dopamine Terminal Toxicity by Preventing Oxidative Stress in the Mouse Brain.

Methamphetamine (METH) is a popular psychostimulant due to its long-lasting effects and inexpensive production. METH intoxication is known to increase oxidative stress leading to neuronal damage. Thus, preventing the METH-induced oxidative stress can potentially mitigate neuronal damage. Previously, our laboratory found that epigallocatechin gallate (EGCG), a strong antioxidant found in green tea, can protect against the METH-induced apoptosis and dopamine terminal toxicity in the striatum of mice. In the present study, we evaluated the anti-oxidative properties of EGCG on the METH-induced oxidative stress using CD-1 mice. First, we demonstrated that mice pretreated with EGCG 30 min prior to the METH injection (30 mg/kg, ip) showed protection against the striatal METH-induced reduction of tyrosine hydroxylase without mitigating hyperthermia. In addition, injecting a single high dose of METH caused the reduction of striatal glutathione peroxidase activity at 24 h after the METH injection. Interestingly, pretreatment with EGCG 30 min prior to the METH injection prevented the METH-induced reduction of glutathione peroxidase activity. Moreover, we utilized Western blots to quantify the glutathione peroxidase 4 protein level in the striatum. The results showed that METH decreased striatal glutathione peroxidase 4 protein level, and the reduction was prevented by EGCG pretreatment. Finally, we observed that the METH-induced increase of striatal catalase and copper/zinc superoxide dismutase protein levels were also attenuated by pretreatment with EGCG. Taken together, our data indicate that EGCG is an effective agent that can be used to mitigate the METH-induced striatal toxicity in the mouse brain.

Pifithrin-Alpha Reduces Methamphetamine Neurotoxicity in Cultured Dopaminergic Neurons.

Methamphetamine (Meth) is a widely abused stimulant. High-dose Meth induces degeneration of dopaminergic neurons through p53-mediated apoptosis. A recent study indicated that treatment with the p53 inhibitor, pifithrin-alpha (PFT-α), antagonized Meth-mediated behavioral deficits in mice. The mechanisms underpinning the protective action of PFT-α against Meth have not been identified, and hence, their investigation is the focus of this study. Primary dopaminergic neuronal cultures were prepared from rat embryonic ventral mesencephalic tissue. High-dose Meth challenge reduced tyrosine hydroxylase immunoreactivity and increased terminal deoxynucleotidyl transferase-mediated dNTP nick-end labeling (TUNEL) labeling. PFT-α significantly antagonized these responses. PFT-α also reduced Meth-activated translocation of p53 to the nucleus, an initial step before transcription. Previous studies have indicated that p53 can also activate cell death through transcription-independent pathways. We found that PFT-α attenuated endoplasmic reticulum (ER) stressor thapsigargin (Tg)-mediated loss of dopaminergic neurons. ER stress was further monitored through the release of Gaussia luciferase (GLuc) from SH-SY5Y cells overexpressing GLuc-based Secreted ER Calcium-Modulated Protein (GLuc-SERCaMP). Meth or Tg significantly increased GLuc release in to the media, with PFT-α significantly reducing GLuc release. Additionally, PFT-α significantly attenuated Meth-induced CHOP expression. In conclusion, our data indicate that PFT-α is neuroprotective against Meth-mediated neurodegeneration via transcription-dependent nuclear and -independent cytosolic ER stress pathways.

Chronic Methylphenidate Alters Tonic and Phasic Glutamate Signaling in the Frontal Cortex of a Freely-Moving Rat Model of ADHD.

Glutamate dysfunction has been implicated in a number of substance of abuse studies, including cocaine and methamphetamine. Moreover, in attention-deficit/hyperactivity disorder (ADHD), it has been discovered that when the initiation of stimulant treatment occurs during adolescence, there is an increased risk of developing a substance use disorder later in life. The spontaneously hypertensive rat (SHR) serves as a phenotype for ADHD and studies have found increased cocaine self-administration in adult SHRs when treated with the stimulant methylphenidate (MPH) during adolescence. For this reason, we wanted to examine glutamate signaling in the pre-limbic frontal cortex, a region implicated in ADHD and drug addiction, in the SHR and its progenitor control strain, the Wistar Kyoto (WKY). We chronically implanted glutamate-selective microelectrode arrays (MEAs) into 8-week-old animals and treated with MPH (2 mg/kg, s.c.) for 11 days while measuring tonic and phasic extracellular glutamate concentrations. We observed that intermediate treatment with a clinically relevant dose of MPH increased tonic glutamate levels in the SHR but not the WKY compared to vehicle controls. After chronic treatment, both the SHR and WKY exhibited increased tonic glutamate levels; however, only the SHR was found to have decreased amplitudes of phasic glutamate signaling following chronic MPH administration. The findings from this study suggest that the MPH effects on extracellular glutamate levels in the SHR may potentiate the response for drug abuse later in life. Additionally, these data illuminate a pathway for investigating novel therapies for the treatment of ADHD and suggest that possibly targeting the group II metabotropic glutamate receptors may be a useful therapeutic avenue for adolescents diagnosed with ADHD.

Striatal Reinnervation Process after Acute Methamphetamine-Induced Dopaminergic Degeneration in Mice.

Methamphetamine (METH), an amphetamine derivate, may increase the risk of developing Parkinson's disease (PD). Human and animal studies have shown that METH produces persistent dopaminergic neurotoxicity in the nigrostriatal pathway, despite initial partial recovery. To determine the processes leading to early compensation, we studied the detailed morphology and distribution of tyrosine hydroxylase immunoreactive fibers (TH-ir) classified by their thickness (types I-IV) before and after METH. Applying three established neurotoxic regimens of METH: single high dose (1 × 30 mg/kg), multiple lower doses (3 × 5 mg/kg) or (3 × 10 mg/kg), we show that METH primarily damages type I fibers (the thinner ones), and to a much lesser extend types II-IV fibers including sterile axons. The striatal TH terminal partial recovery process, consisting of a progressive regrowth increases in types II, III, and IV fibers, demonstrated by co-localization of GAP-43, a sprouting marker, was observed 3 days post-METH treatment. In addition, we demonstrate the presence of growth-cone-like TH-ir structures, indicative of new terminal generation as well as improvement in motor functions after 3 days. A temporal relationship was observed between decreases in TH-expression and increases in silver staining, a marker of degeneration. Striatal regeneration was associated with an increase in astroglia and decrease in microglia expression, suggesting a possible role for the neuroimmune system in regenerative processes. Identification of regenerative compensatory mechanisms in response to neurotoxic agents could point to novel mechanisms in countering the neurotoxicity and/or enhancing the regenerative processes.

Methamphetamine toxicity-induced calcineurin activation, nuclear translocation of nuclear factor of activated T-cells and elevation of cyclooxygenase 2 levels are averted by calpastatin overexpression in neuroblastoma SH-SY5Y cells.

Methamphetamine (METH) is an addictive stimulant drug that has many negative consequences, including toxic effects to the brain. Recently, the induction of inflammatory processes has been identified as a potential contributing factor to induce neuronal cell degeneration. It has been demonstrated that the expression of inflammatory agents, such as cyclooxygenase 2 (COX-2), depends on the activation of calcineurin (CaN) and nuclear factor of activated T-cells (NFAT). Moreover, the excessive elevation in cytosolic Ca2+ levels activates the cell death process, including calpain activation in neurons, which was diminished by the overexpression of the calpain inhibitor protein, calpastatin. However, it is unclear whether calpain mediates CaN-NFAT activation in the neurotoxic process. In the present study, we observed that the toxic high dose of METH-treated neuroblastoma SH-SY5Y cells significantly decreased cell viability but increased apoptotic cell death, the active cleaved form of calcineurin, the nuclear translocation of NFAT, and COX-2 levels. Nevertheless, these toxic effects were diminished in METH-treated calpastatin-overexpressing SH-SY5Y cells. These findings might emphasize the role of calpastatin against METH-induced toxicity by a mechanism related to calpain-dependent CaN-NFAT activation-induced COX-2 expression.

Alcohol, psychomotor-stimulants and behaviour: methodological considerations in preclinical models of early-life stress.

BACKGROUND: In order to assess the risk associated with early-life stress, there has been an increase in the amount of preclinical studies investigating early-life stress. There are many challenges associated with investigating early-life stress in animal models and ensuring that such models are appropriate and clinically relevant. OBJECTIVES: The purpose of this review is to highlight the methodological considerations in the design of preclinical studies investigating the effects of early-life stress on alcohol and psychomotor-stimulant intake and behaviour. METHODS: The protocols employed for exploring early-life stress were investigated and summarised. Experimental variables include animals, stress models, and endpoints employed. RESULTS: The findings in this paper suggest that there is little consistency among these studies and so the interpretation of these results may not be as clinically relevant as previously thought. CONCLUSION: The standardisation of these simple stress procedures means that results will be more comparable between studies and that results generated will give us a more robust understanding of what can and may be happening in the human and veterinary clinic.

Development of a Functional Observational Battery in the Minipig for Regulatory Neurotoxicity Assessments.

A functional observational battery (FOB) is recommended as the first-tier neurotoxicity screening in the preclinical safety pharmacology testing guidelines. Minipigs have increasingly been used in regulatory toxicology studies; however, no current FOB protocol is available for neurotoxicity testing in these species. Hence, a minipig FOB instrument was developed. A complete crossover study with Sinclair minipigs was performed to evaluate physiologic, neurologic, and behavioral effects of amphetamine, ketamine, and diazepam. The treated minipigs were first observed in their home cage, were video-recorded for 10 minutes in an open field, and then went through a complete neurologic examination. Both ketamine and diazepam were shown to reduce the freezing and behavior shifts of treated minipigs, while increasing their exploratory behaviors. Both drugs also caused muscular and gait impairment. The effects of ketamine and diazepam were consistent with their roles as central nervous system (CNS) suppressants. Unique effects were also observed with ketamine and diazepam treatments, which may reflect their unique mechanisms of action. Consistent with its role as a CNS stimulant, amphetamine caused the treated minipigs to be hyperactive and to display increased freezing and behavior shifts and reduced exploring activities. These effects of amphetamine were opposite to those observed with ketamine and diazepam. Amphetamine also increased locomotion in the treated minipigs. The present effects of amphetamine, ketamine, and diazepam are in agreement with observations by others. In conclusion, the minipig is a suitable species for FOB evaluation of pharmaceuticals in preclinical safety pharmacology testing.

Pharmacological activation of the neurotensin receptor 1 abrogates the methamphetamine-induced striatal apoptosis in the mouse brain.

Methamphetamine (METH) is a widely abused psychostimulant displaying potent addictive and neurotoxic properties. METH induces neurotoxicity of dopaminergic terminals and striatal neurons in the striatum. Despite much information on neurotransmitters, the role of neuropeptides is poorly understood. In this study, we investigated the role of the neuropeptide neurotensin on the METH-induced apoptosis of some striatal neurons in mice. We observed that a single injection of METH (30mg/kg, ip) induced the loss of approximately 15% of striatal neurons. An agonist of the neurotensin receptor 1 (PD149163, ip at various doses) attenuated the METH-induced striatal neuron apoptosis. Utilizing quantitative real time PCR, we showed that METH also up-regulated neurotensin gene expression with 96% increase in preproneurotensin mRNA levels in the striatum as compared to the control. Additionally, NTR1 agonist (ip injection) attenuated hyperthermia at 2h post-METH injection; hyperthermia is a putative and significant component of METH-induced neurotoxicity. To investigate the role of neurotensin without affecting core body temperature, we performed stereotactic injection of PD149163 into the striatum and observed that this compound maintained attenuated the METH-induced apoptosis in the striatum, while leaving core body temperature unaffected. There was no effect of NTR1 agonist on METH-induced dopamine terminal degeneration, as evidenced by tyrosine hydroxylase levels determined by Western blot. These data indicate that the neuropeptide neurotensin modulates the striatal neuronal apoptosis induced by METH through diverse mechanisms that need to be investigated. Furthermore, due to its neuroprotective properties, neurotensin receptor agonists show potential as drug candidates for the treatment of METH abuse and some neurological disorders.

Methamphetamine Induces Anhedonic-Like Behavior and Impairs Frontal Cortical Energetics in Mice.

INTRODUCTION: We recently showed that a single high dose of methamphetamine (METH) induces a persistent frontal cortical monoamine depletion that is accompanied by helpless-like behavior in mice. However, brain metabolic alterations underlying both neurochemical and mood alterations remain unknown. AIMS: Herein, we aimed at characterizing frontal cortical metabolic alterations associated with early negative mood behavior triggered by METH. Adult C57BL/6 mice were injected with METH (30 mg/kg, i.p.), and their frontal cortical metabolic status was characterized after probing their mood and anxiety-related phenotypes 3 days postinjection. RESULTS: Methamphetamine induced depressive-like behavior, as indicated by the decreased grooming time in the splash test and by a transient decrease in sucrose preference. At this time, METH did not alter anxiety-like behavior or motor functions. Depolarization-induced glucose uptake was reduced in frontocortical slices from METH-treated mice compared to controls. Consistently, astrocytic glucose transporter (GluT1) density was lower in the METH group. A proton high rotation magic angle spinning (HRMAS) spectroscopic approach revealed that METH induced a significant decrease in N-acetyl aspartate (NAA) and glutamate levels, suggesting that METH decreased neuronal glutamatergic function in frontal cortex. CONCLUSIONS: We report, for the first time, that a single METH injection triggers early self-care and hedonic deficits and impairs frontal cortical energetics in mice.

Effects of repeated high-dose methamphetamine and ceftriaxone post-treatments on tissue content of dopamine and serotonin as well as glutamate and glutamine.

Repeated exposure to high doses of methamphetamine (METH) is known to alter several neurotransmitters in certain brain regions. Little is known about the effects of ceftriaxone (CEF), a ß-lactam antibiotic, known to upregulate glutamate transporter subtype 1, post-treatment on METH-induced depletion of dopamine and serotonin (5-HT) tissue content in brain reward regions. Moreover, the effects of METH and CEF post-treatment on glutamate and glutamine tissue content are not well understood. In this study, Wistar rats were used to investigate the effects of METH and CEF post-treatment on tissue content of dopamine/5-HT and glutamate/glutamine in the nucleus accumbens (NAc) and prefrontal cortex (PFC). Rats received either saline or METH (10mg/kg, i.p. every 2h×4) followed by either saline or CEF (200mg/kg, i.p, every day×3) post-treatment. METH induced a significant depletion of dopamine and 5-HT in the NAc and PFC. Importantly, dopamine tissue content was completely restored in the NAc following CEF post-treatment. Additionally, METH caused a significant decrease in glutamate and glutamine tissue content in PFC, and this effect was attenuated by CEF post-treatment. These findings demonstrate for the first time the attenuating effects of CEF post-treatment on METH induced alterations in the tissue contents of dopamine, glutamate, and glutamine.

Microglia response in retina and optic nerve in chronic experimental autoimmune encephalomyelitis.

Experimental autoimmune encephalomyelitis (EAE) is a common rodent model for multiple sclerosis (MS). Yet, the long-term consequences for retina and optic nerve (ON) are unknown. C57BL/6 mice were immunized with an encephalitogenic peptide (MOG35-55) and the controls received the carriers or PBS. Clinical symptoms started at day 8, peaked at day 14, and were prevalent until day 60. They correlated with infiltration and demyelination of the ON. In MOG-immunized animals more microglia cells in the ONs and retinas were detected at day 60. Additionally, retinal ganglion cell (RGC) loss was combined with an increased macroglia response. At this late stage, an increased number of microglia was associated with axonal damage in the ON and in the retina with RGC loss. Whether glial activation contributes to repair mechanisms or adversely affects the number of RGCs is currently unclear.

The neuroprotective effect of lithium against high dose methylphenidate: Possible role of BDNF.

Methylphenidate (MPH) is a neural stimulant with unclear neurochemical and behavioral effects. Lithium is a neuroprotective agent in use clinically for the management of manic-depressive and other neurodegenerative disorders. This study investigated the protective effect of lithium on MPH-induced oxidative stress, anxiety, depression and cognition impairment. Forty-eight adult male rats were divided randomly and equally into 6 groups. Treatment groups were received MPH (10mg/kg) and various doses of lithium (75, 150 and 300mg/kg) simultaneously and also lithium (150mg/kg) alone for 21 days. Elevated Plus Maze and Forced Swim Test were used to determine the level of anxiety and depression in animals. Morris Water Maze was used to evaluate spatial learning and memory. The hippocampi of rats were isolated and the level and activity of oxidative, anti-oxidant and inflammatory factors were measured. Also brain derived neurotropic factor expression level was measured by RT-PCR and western blotting. MPH (10mg/kg) caused behaviors indicative of anxiety and depression-like phenotypes in EPM and FST and cognition impairment in MWM. While lithium in all mentioned doses inhibited these effects. Treatment with MPH significantly increased lipid peroxidation, mitochondrial GSH content and IL-1ß and TNF-α levels in isolated hippocampal cells. Moreover superoxide dismutase and glutathione peroxidase activities and BDNF expression remarkably decreased. Various doses of lithium attenuated these effects and significantly mitigated MPH-induced oxidative damage, inflammation and increased BDNF expression level. Lithium has the potential to act as a neuroprotective agent against MPH induced toxicity in rat brain and this might be mediated by BDNF expression in hippocampus of rats.

Effect of Methamphetamine Exposure on Expression of Calcium Binding Proteins in Rat Frontal Cortex and Hippocampus.

Methamphetamine (METH) is a psychostimulant drug with potent effects on the central nervous system that can cause psychotic symptoms similar to those of schizophrenia. Specific alterations in GABAergic neuronal markers have been reported in schizophrenia and animal models of psychotic illness. The aim of this study was to determine whether there are changes in subpopulations of GABAergic neurons, defined by the presence of calcium binding proteins (CBPs), in animal models of METH abuse. Rats received acute (Binge) doses of 4 × 6 mg/kg, a chronic escalating dose regime (0.1-4 mg/kg over 14 days) or a combination of the two and were compared with a vehicle-administered control group. Brains were taken and sections of frontal cortex (Cg1) and hippocampus (dentate gyrus and CA1-3 regions) underwent immunostaining for three CBPs [parvalbumin (PV), calbindin (CB), and calretinin (CR)]. Significant decreases in PV-immunoreactive (IR) neurons in each METH group and all regions were observed. Smaller METH-induced deficits in CB-IR cells were observed, reaching significance primarily following chronic METH regimes, while CR-IR was significantly reduced only in frontal cortex following chronic administration. These results suggest that METH regimes in rats can induce selective deficits in GABAergic neuronal subtypes similar to those seen in schizophrenia and may underlie the psychosis and/or cognitive impairment that can occur in METH abuse and dependence.

The "induced hyperactivity" test for the de-risking of potential off-target activity of antihypertensive drugs.

INTRODUCTION: Compound X is a new proprietary antihypertensive agent that induces its pharmacodynamic effect at an approximate plasma Cmax.u of 0.6nmol/L (rat hypertension model). However, Compound X also shows potent off-target activity at PDE-10a (IC50~12nmol/L). Since PDE-10a is expressed predominantly in brain (striatum) and inhibition/knockout of PDE-10a have been reported to result in anti-psychotic effects, we have established the "induced hyperactivity" test for CNS de-risking of Compound X. METHODS: Male Wistar rats treated orally with vehicle or Compound X (single dose; 1-3-10mg/kg) were assessed for exploratory locomotor activity following induction of hyperactivity by d-amphetamine (2mg/kg) or the NMDA antagonist MK-801 (0.2mg/kg). The assay was validated with anti-psychotic drugs (haloperidol, clozapine). RESULTS: Induced hyperactivity was not antagonized by Compound X at doses relevant for its primary pharmacodynamic activity (0.1-0.3mg/kg, rat). Although sufficient plasma concentrations were reached with Compound X (Cmax.u up to ~8nmol/L at 10mg/kg) to show its PDE-10a activity, its low brain penetration (~10%) likely precluded any meaningful PDE-10a inhibition. In comparison, other blood pressure lowering agents such as prazosin (alpha-1 adrenoceptor antagonist) and isradipine (L-Type Ca(2+) channel blocker), but not the NO-donor ISDN, tended to attenuate induced hyperactivity in rats at high doses. CONCLUSION: The relevance of a potent in-vitro off-target hit (PDE-10a inhibition) by Compound X was attenuated by a robust in-vivo assay (rat induced hyperactivity test), hence lowering the potential liability profile of Compound X. Finally, this piece of investigative safety pharmacology work enabled early de-risking of Compound X based on its primary pharmacodynamic activity in a relevant rat model.

Effects of dehydroepiandrosterone in amphetamine-induced schizophrenia models in mice.

OBJECTIVE: To examine the effects of dehydroepiandrosterone (DHEA) on animal models of schizophrenia. METHODS: Seventy Swiss albino female mice (25-35 g) were divided into 4 groups: amphetamine-free (control), amphetamine, 50, and 100 mg/kg DHEA. The DHEA was administered intraperitoneally (ip) for 5 days. Amphetamine (3 mg/kg ip) induced hyper locomotion, apomorphine (1.5 mg/kg subcutaneously [sc]) induced climbing, and haloperidol (1.5 mg/kg sc) induced catalepsy tests were used as animal models of schizophrenia. The study was conducted at the Animal Experiment Laboratories, Department of Pharmacology, Medical School, Eskisehir Osmangazi University, Eskisehir, Turkey between March and May 2012. Statistical analysis was carried out using Kruskal-Wallis test for hyper locomotion, and one-way ANOVA for climbing and catalepsy tests. RESULTS: In the amphetamine-induced locomotion test, there were significant increases in all movements compared with the amphetamine-free group. Both DHEA 50 mg/kg (p<0.05), and 100 mg/kg (p<0.01) significantly decreased all movements compared with the amphetamine-induced locomotion group. There was a significant difference between groups in the haloperidol-induced catalepsy test (p<0.05). There was no significant difference between groups in terms of total climbing time in the apomorphine-induced climbing test (p>0.05). CONCLUSION: We observed that DHEA reduced locomotor activity and increased catalepsy at both doses, while it had no effect on climbing behavior. We suggest that DHEA displays typical neuroleptic-like effects, and may be used in the treatment of schizophrenia.