Pathological polarizations from microglia to astrocyte contributes to spatial memory deficit in methamphetamine abstinence mice.

Previously, we found that dCA1 A1-like polarization of astrocytes contributes a lot to the spatial memory deficit in methamphetamine abstinence mice. However, the underlying mechanism remains unclear, resulting in a lack of promising therapeutic targets. Here, we found that methamphetamine abstinence mice exhibited an increased M1-like microglia and A1-like astrocytes, together with elevated levels of interleukin 1α and tumor necrosis factor α in dCA1. In vitro, the M1-like BV2 microglia cell medium, containing high levels of Interleukin 1α and tumor necrosis factor α, elevated A1-like polarization of astrocytes, which weakened their capacity for glutamate clearance. Locally suppressing dCA1 M1-like microglia activation with minocycline administration attenuated A1-like polarization of astrocytes, ameliorated dCA1 neurotoxicity, and, most importantly, rescued spatial memory in methamphetamine abstinence mice. The effective time window of minocycline treatment on spatial memory is the methamphetamine exposure period, rather than the long-term methamphetamine abstinence.

IL-10 and Cdc42 modulate astrocyte-mediated microglia activation in methamphetamine-induced neuroinflammation.

Methamphetamine (Meth) use is known to induce complex neuroinflammatory responses, particularly involving astrocytes and microglia. Building upon our previous research, which demonstrated that Meth stimulates astrocytes to release tumor necrosis factor (TNF) and glutamate, leading to microglial activation, this study investigates the role of the anti-inflammatory cytokine interleukin-10 (IL-10) in this process. Our findings reveal that the presence of recombinant IL-10 (rIL-10) counteracts Meth-induced excessive glutamate release in astrocyte cultures, which significantly reduces microglial activation. This reduction is associated with the modulation of astrocytic intracellular calcium (Ca2+) dynamics, particularly by restricting the release of Ca2+ from the endoplasmic reticulum to the cytoplasm. Furthermore, we identify the small Rho GTPase Cdc42 as a crucial intermediary in the astrocyte-to-microglia communication pathway under Meth exposure. By employing a transgenic mouse model that overexpresses IL-10 (pMT-10), we also demonstrate in vivo that IL-10 prevents Meth-induced neuroinflammation. These findings not only enhance our understanding of Meth-related neuroinflammatory mechanisms, but also suggest IL-10 and Cdc42 as putative therapeutic targets for treating Meth-induced neuroinflammation.

Amphetamine exposure during embryogenesis changes expression and function of the dopamine transporter in Caenorhabditis elegans offspring.

The dopamine transporter (DAT) is a transmembrane protein that regulates dopamine (DA) neurotransmission by binding to and moving DA from the synaptic cleft back into the neurons. Besides moving DA and other endogenous monoamines, DAT is also a neuronal carrier for exogenous compounds such as the psychostimulant amphetamine (Amph), and several studies have shown that Amph-induced behaviors require a functional DAT. Here, we demonstrate that exposure to Amph during early development causes behavioral, functional, and epigenetic modifications at the Caenorhabditis elegans DAT gene homolog, dat-1, in C. elegans offspring. Specifically, we show that, while embryos exposed to Amph generate adults that produce offspring with no obvious behavioral alterations, both adults and offspring exhibit an increased behavioral response when challenged with Amph. Our functional studies suggest that a decrease in DAT-1 expression underlies the increased behavioral response to Amph seen in offspring. Moreover, our epigenetic data suggest that histone methylation is a mechanism utilized by Amph to maintain changes in DAT-1 expression in offspring. Taken together, our data reveal that Amph, by altering the epigenetic landscape of DAT, propagates long-lasting functional and behavioral changes in offspring.

Life-long impairment of glucose homeostasis upon prenatal exposure to psychostimulants.

Maternal drug abuse during pregnancy is a rapidly escalating societal problem. Psychostimulants, including amphetamine, cocaine, and methamphetamine, are amongst the illicit drugs most commonly consumed by pregnant women. Neuropharmacology concepts posit that psychostimulants affect monoamine signaling in the nervous system by their affinities to neurotransmitter reuptake and vesicular transporters to heighten neurotransmitter availability extracellularly. Exacerbated dopamine signaling is particularly considered as a key determinant of psychostimulant action. Much less is known about possible adverse effects of these drugs on peripheral organs, and if in utero exposure induces lifelong pathologies. Here, we addressed this question by combining human RNA-seq data with cellular and mouse models of neuroendocrine development. We show that episodic maternal exposure to psychostimulants during pregnancy coincident with the intrauterine specification of pancreatic ß cells permanently impairs their ability of insulin production, leading to glucose intolerance in adult female but not male offspring. We link psychostimulant action specifically to serotonin signaling and implicate the sex-specific epigenetic reprogramming of serotonin-related gene regulatory networks upstream from the transcription factor Pet1/Fev as determinants of reduced insulin production.

Caffeine upregulates SIRT3 expression to ameliorate astrocytes-mediated HIV-1 Tat neurotoxicity via suppression of EGR1 signaling pathway.

Caffeine is one of the most popular consumed psychostimulants that mitigates several neurodegenerative diseases. Nevertheless, the roles and molecular mechanisms of caffeine in HIV-associated neurocognitive disorders (HAND) remain largely unclear. Transactivator of transcription (Tat) is a major contributor to the neuropathogenesis of HAND in the central nervous system. In the present study, we determined that caffeine (100 µM) treatment significantly ameliorated Tat-induced decreased astrocytic viability, oxidative stress, inflammatory response and excessive glutamate and ATP release, thereby protecting neurons from apoptosis. Subsequently, SIRT3 was demonstrated to display neuroprotective effects against Tat during caffeine treatment. In addition, Tat downregulated SIRT3 expression via activation of EGR1 signaling, which was reversed by caffeine treatment in astrocytes. Overexpression of EGR1 entirely abolished the neuroprotective effects of caffeine against Tat. Furthermore, counteracting Tat or caffeine-induced differential expression of SIRT3 abrogated the neuroprotection of caffeine against Tat-triggered astrocytic dysfunction and neuronal apoptosis. Taken together, our study establishes that caffeine ameliorates astrocytes-mediated Tat neurotoxicity by targeting EGR1/SIRT3 signaling pathway. Our findings highlight the beneficial effects of caffeine on Tat-induced astrocytic dysfunction and neuronal death and propose that caffeine might be a novel therapeutic drug for relief of HAND.

Can exposure to lisdexamfetamine dimesylate from juvenile period to peripubertal compromise male reproductive parameters in adult rats?

Lisdexamfetamine (LDX) is a d-amphetamine prodrug used to treat attention deficit and hyperactivity disorder, a common neurodevelopmental disorder in children and adolescents. Due to its action mediated by elevated levels of catecholamines, mainly dopamine and noradrenaline, which influence hormonal regulation and directly affect the gonads, this drug may potentially disrupt reproductive performance. This study evaluated the effects of exposure to LDX from the juvenile to peripubertal period (critical stages of development) on systemic and reproductive toxicity parameters in male rats. Male Wistar rats (23 days old) were treated with 0; 5.2; 8.6 or 12.1 mg/kg/day of LDX from post-natal day (PND) 23 to 53, by gavage. LDX treatment led to reduced daily food and water consumption, as well as a decrease in social behaviors. The day of preputial separation remained unaltered, although the treated animals exhibited reduced weight. At PND 54, the treated animals presented signs of systemic toxicity, evidenced by a reduction in body weight gain, increase in the relative weight of the liver, spleen, and seminal gland, reduction in erythrocyte and leukocyte counts, reduced total protein levels, and disruptions in oxidative parameters. In adulthood, there was an increase in immobile sperm, reduced sperm count, morphometric changes in the testis, and altered oxidative parameters, without compromising male sexual behavior and fertility. These findings showed that LDX-treatment during the juvenile and peripubertal periods induced immediate systemic toxicity and adversely influenced reproductive function in adult life, indicating that caution is necessary when prescribing this drug during the peripubertal phase.

The gut microbiota contributes to methamphetamine-induced reproductive toxicity in male mice.

Methamphetamine (METH) is a psychostimulant drug belonging to the amphetamine-type stimulant class, known to exert male reproductive toxicity. Recent studies suggest that METH can disrupt the gut microbiota. Furthermore, the gut-testis axis concept has gained attention due to the potential link between gut microbiome dysfunction and reproductive health. Nonetheless, the role of the gut microbiota in mediating the impact of METH on male reproductive toxicity remains unclear. In this study, we employed a mouse model exposed to escalating doses of METH to assess sperm quality, testicular pathology, and reproductive hormone levels. The fecal microbiota transplantation method was employed to investigate the effect of gut microbiota on male reproductive toxicity. Transcriptomic, metabolomic, and microbiological analyses were conducted to explore the damage mechanism to the male reproductive system caused by METH. We found that METH exposure led to hormonal disorders, decreased sperm quality, and changes in the gut microbiota and testicular metabolome in mice. Testicular RNA sequencing revealed enrichment of several Gene Ontology terms associated with reproductive processes, as well as PI3K-Akt signaling pathways. FMT conveyed similar reproductive damage from METH-treated mice to healthy recipient mice. The aforementioned findings suggest that the gut microbiota plays a substantial role in facilitating the reproductive toxicity caused by METH, thereby highlighting a prospective avenue for therapeutic intervention in the context of METH-induced infertility.

Synthetic Cathinones and Neurotoxicity Risks: A Systematic Review.

According to the EU Early Warning System (EWS), synthetic cathinones (SCs) are the second largest new psychoactive substances (NPS) class, with 162 synthetic cathinones monitored by the EU EWS. They have a similar structure to cathinone, principally found in Catha Edulis; they have a phenethylamine related structure but also exhibit amphetamine-like stimulant effects. Illegal laboratories regularly develop new substances and place them on the market. For this reason, during the last decade this class of substances has presented a great challenge for public health and forensic toxicologists. Acting on different systems and with various mechanisms of action, the spectrum of side effects caused by the intake of these drugs of abuse is very broad. To date, most studies have focused on the substances' cardiac effects, and very few on their associated neurotoxicity. Specifically, synthetic cathinones appear to be involved in different neurological events, including increased alertness, mild agitation, severe psychosis, hyperthermia and death. A systematic literature search in PubMed and Scopus databases according to PRISMA guidelines was performed. A total of 515 studies published from 2005 to 2022 (350 articles from PubMed and 165 from Scopus) were initially screened for eligibility. The papers excluded, according to the criteria described in the Method Section (n = 401) and after full text analyses (n = 82), were 483 in total. The remaining 76 were included in the present review, as they met fully the inclusion criteria. The present work provides a comprehensive review on neurotoxic mechanisms of synthetic cathinones highlighting intoxication cases and fatalities in humans, as well as the toxic effects on animals (in particular rats, mice and zebrafish larvae). The reviewed studies showed brain-related adverse effects, including encephalopathy, coma and convulsions, and sympathomimetic and hallucinogenic toxidromes, together with the risk of developing excited/agitated delirium syndrome and serotonin syndrome.

Behavioural and neurochemical effects after repeated administration of N-ethylpentylone (ephylone) in mice.

N-ethyl-pentylone (NEP), also known as 'ephylone' and N-ethylnorpentylone, has been identified as one of the most recent novel psychostimulants to emerge into the illicit drug market and it has been associated with some intoxications and even fatalities. However, little is known about the consequences of its repeated consumption as well as the role of the monoaminergic system in such consequences. Thus, the aim of our study was to investigate the neurochemical profile and the behavioural effects after both acute and repeated NEP exposure. Male OF1 mice were acutely (1, 3, 10 mg/kg, i.p.) or repeatedly (1, 3, 10 mg/kg, i.p., 5 days, twice/day) exposed to NEP, and anxiety-like behaviour, aggressiveness, social interaction, depressive-like symptoms, body temperature, changes in monoaminergic enzymes and neurotransmitters levels as well as ΔFosB in striatum and prefrontal cortex (PFC) from post-mortem tissue were analysed short after drug-exposure or during drug-withdrawal. Acute administration of NEP induced anxiolytic effects but also an aggressive behaviour and social exploration deficits in mice, which persist during NEP-withdrawal. Moreover, NEP induced hyperthermia as well as depressive-like symptoms after repeated administrations that may be related to the decrease in serotonin and noradrenaline levels observed in striatum and PFC. Finally, the long-term increase in ΔFosB levels in striatum after NEP chronic exposure points to a high risk of dependence. Altogether indicates that NEP consumption induces different neurological and neuropsychiatric disorders accompanied by changes in the monoaminergic system, posing a threat to public health.

Methamphetamine exposure induces neuronal programmed necrosis by activating the receptor-interacting protein kinase 3 -related signalling pathway.

Methamphetamine (METH) is a synthetic drug with severe neurotoxicity, however, the regulation of METH-induced neuronal programmed necrosis remains poorly understood. The aim of this study was to identify the molecular mechanisms of METH-induced neuronal programmed necrosis. We found that neuronal programmed necrosis occurred in the striatum of brain samples from human and mice that were exposed to METH. The receptor-interacting protein kinase 3 (RIP3) was highly expressed in the neurons of human and mice exposed to METH, and RIP3-silenced or RIP1-inhibited protected neurons developed neuronal programmed necrosis in vitro and in vivo following METH exposure. Moreover, the RIP1-RIP3 complex causes cell programmed necrosis by regulating mixed lineage kinase domain-like protein (MLKL)-mediated cell membrane rupture and dynamin-related protein 1 (Drp1)-mediated mitochondrial fission. Together, these data indicate that RIP3 plays an indispensable role in the mechanism of METH-induced neuronal programmed necrosis, which may represent a potential therapeutic target for METH-induced neurotoxicity.

The Crosstalk Between Neurons and Glia in Methamphetamine-Induced Neuroinflammation.

Methamphetamine (METH), an illicit psycho-stimulant, is widely known as an addictive drug that may cause neurotoxic effects. Previous researches on METH abuse have mainly focused on neurotransmitters, such as dopamine and glutamate. However, there is growing evidence that neuroinflammation also plays an important role in the etiology and pathophysiology of brain dysfunction induced by METH abuse. This has cast a spotlight on the research of microglia and astrocyte, which are critical mediators of neuroimmune pathology in recent years. In the central nervous system (CNS) immunity, abnormalities of the microglia and astrocytes have been observed in METH abusers from both postmortem and preclinical studies. The bidirectional communication between neurons and glia is essential for the homeostasis and biological function of the CNS while activation of glia induces the release of cytokines and chemokines during pathological conditions, which will affect the neuron-glia interactions and lead to adverse behavioral consequences. However, the underlying mechanisms of interaction between neurons and glia in METH-induced neuroinflammation remain elusive. Notably, discovering and further understanding glial activity and functions, as well as the crosstalk between neurons and glia may help to explain the pathogenesis of METH abuse and behavioral changes in abusers. In this review, we will discuss the current understanding of the crosstalk between neurons and glia in METH-induced neuroinflammation. We also review the existing microglia-astrocyte interaction under METH exposure. We hope the present review will lead the way for more studies on the development of new therapeutic strategies for METH abuse in the near future.

The effects of minocycline in improving of methamphetamine withdrawal syndrome in male mice.

Methamphetamine (METH) is a potent psychostimulant drug with an increasing rate of abuse over recent years. Depressive-like behaviors are one of the major symptoms patients in the METH withdrawal period experience. There is limited evidence regarding the METH withdrawal treatment, and conventional managements are not completely effective. Furthermore, extensive promising literature supports minocycline, a well-known antibiotic with anti-oxidant, anti-inflammatory properties, to treat depressive-like behaviors. Therefore, we hypothesized that administration of minocycline might mitigate the methamphetamine (METH) induced depression in male mice. Administration of METH (2 mg/kg) to mice two times a day for 14 constitutive days was done to induce the METH-induced withdrawal syndrome model. Animals were divided into 10 groups (n = 10 in each group), and three doses of minocycline (2.5, 5 and 10 mg/kg) were daily administered to male albino mice for 10 days. Following the behavioral test, the animals were scarified, their hippocampus were dissected to measure oxidative stress parameters. Our data revealed that chronic administration of minocycline provoked antidepressant effects in behavioral tests, such as forced swim test (FST), tail suspension test (TST) and splash test. Additionally, minocycline was able to improve oxidative stresses and neuronal damage in the hippocampus and restore the body's antioxidant system by increasing glutathione (GSH) and the cellular energy (ATP) and reducing the malondialdehyde (MDA) level. According to our promising results of minocycline on targeting mitochondria and its performance, we suggest minocycline as a new therapeutic option in clinical trials of depression treatment.

Altered metabolic pathways elucidated via untargeted in vivo toxicometabolomics in rat urine and plasma samples collected after controlled application of a human equivalent amphetamine dose.

Amphetamine is widely consumed as drug of abuse due to its stimulating and cognitive enhancing effects. Since amphetamine has been on the market for quite a long time and it is one of the most commonly used stimulants worldwide, to date there is still limited information on its effects on the metabolome. In recent years, untargeted toxicometabolomics have been increasingly used to study toxicity-related pathways of such drugs of abuse to find and identify important endogenous and exogenous biomarkers. In this study, the acute effects of amphetamine intake on plasma and urinary metabolome in rats were investigated. For this purpose, samples of male Wistar rats after a single dose of amphetamine (5 mg/kg) were compared to a control group using an untargeted metabolomics approach. Analysis was performed using normal and reversed phase liquid chromatography coupled to high-resolution mass spectrometry using positive and negative ionization mode. Statistical evaluation was performed using Welch's two-sample t test, hierarchical clustering, as well as principal component analysis. The results of this study demonstrate a downregulation of amino acids in plasma samples after amphetamine exposure. Furthermore, four new potential biomarkers N-acetylamphetamine, N-acetyl-4-hydroxyamphetamine, N-acetyl-4-hydroxyamphetamine glucuronide, and amphetamine succinate were identified in urine. The present study complements previous data and shows that several studies are necessary to elucidate altered metabolic pathways associated with acute amphetamine exposure.

Mystery of methamphetamine-induced autophagosome accumulation in hippocampal neurons: loss of syntaxin 17 in defects of dynein-dynactin driving and autophagosome-late endosome/lysosome fusion.

Methamphetamine (METH), a psychoactive-stimulant facilitates massive accumulation of autophagosomes and causes autophagy-associated neuronal death. However, the underlying mechanisms involving METH-induced auto-phagosome accumulation remain poorly understood. In the current study, autophagic flux was tracked by mRFP-GFP-LC3 adenovirus, 900 µM METH treatment was found to significantly disrupt autophagic flux, which was further validated by remarkable increase of co-localized of LC3 and SQSTM1/p62, enhancement of LC3-II and SQSTM1/p62 protein levels, and massive autophagosome puncta aggregation. With the cycloheximide (CHX) treatment, METH treatment was displayed a significant inhibition of SQSTM1/p62 degradation. Therefore, the mRNAs associated with vesicle degradation were screened, and syntaxin 17 (Stx17) and dynein-dynactin mRNA levels significantly decreased, an effect was proved in protein level as well. Intriguingly, METH induced autophagosome accumulation and autophagic flux disturbance was incredibly retarded by overexpression of Stx17, which was validated by the restoration of the fusion autophagosome-late endosome/lysosome fusion. Moreover, Stx17 overexpression obviously impeded the METH-induced decrease of co-localization of the retrograded motor protein dynein/dynactin and autophagosome-late endosome, though the dynein/dynactin proteins were not involved in autophagosome-late endosome/lysosome fusion. Collectively, our findings unravel the mechanism of METH-induced autophagosome accumulation involving autophagosome-late endosome/lysosome fusion deficiency and that autophagy-enhancing mechanisms such as the overexpression of Stx17 may be therapeutic strategies for the treatment of METH-induced neuronal damage.

Cannabidiol promotes neurogenesis in the dentate gyrus during an abstinence period in rats following chronic exposure to methamphetamine.

Chronic methamphetamine (meth) abuse can lead to certain deficits in the hippocampal function by affecting the hippocampal neurogenesis and plasticity. To determine whether cannabidiol (CBD) can promote proliferation and maturation of neuronal progenitor cells, this study investigated the CBD effect on neurogenesis in the hippocampal dentate gyrus (DG) following chronic exposure to meth in rats. The rats received 2 mg/kg of meth twice a day for ten days. Next, immunofluorescence was performed to evaluate the effect of intracerebroventricular (ICV) administration of CBD (50 µg/5 µL) over an abstinence period (ten days) on the expression levels of neurogenesis markers, such as Ki67, NeuN, and doublecortin (DCX). Moreover, neuronal degeneration in the hippocampus was assessed using Nissl staining. According to our findings, repeated ICV administration of CBD improved cell proliferation and neurogenesis and increased the number of Ki-67 and DCX-positive cells in the abstinence period. Meanwhile, meth treatment subjects caused a significant decrease in the number of neurogenesis makers, as compared to the control group. The neurogenesis markers (Ki-67 and DCX) could be somewhat reversed, while NeuN did not show any significant increase in the CBD group. Our findings demonstrated that CBD can induce neuroprotective effects by modulating neurogenesis. Therefore, it can provide a promising therapeutic approach to improve cognitive performance following chronic exposure to psychostimulant drugs, including meth.

Combined Cardiopulmonary Assessments Using Impedance and Digital Implants in Conscious Freely Moving Cynomolgus Monkeys, Beagle Dogs, and Göttingen Minipigs: Pharmacological Characterization and Social Housing Effects.

Respiratory monitoring, using impedance with implanted telemetry in socially housed animals, was not possible until the recent development of digital signal transmission. The objective of this study was to evaluate digital telemetry monitoring of cardiopulmonary parameters (respiratory rate, tidal volume, minute volume, electrocardiography (DII), systemic arterial blood pressure, physical activity, and body temperature) in conscious, single-housed, non-rodent species commonly used in toxicology studies following administration of positive/negative controls (saline, dexmedetomidine, morphine, amphetamine, and doxapram), and also, the effects of various social housing arrangements in untreated female and/or male cynomolgus monkeys, Beagle dogs, and Göttingen minipigs (n = 4 per species). Aggressions were observed in socially housed male minipigs, however, which prevented pair-housed assessments in this species. All tested pharmacological agents significantly altered more than one organ system, highlighting important inter-organ dependencies when analyzing functional endpoints. Stress-related physiological changes were observed with single-housing or pair-housing with a new cage mate in cynomolgus monkeys and Beagle dogs, suggesting that stable social structures are preferable to limit variability, especially around dosing. Concomitant monitoring of cardiovascular and respiratory parameters from the same animals may help reduce the number of animals (3 Rs) needed to fulfill the S7A guidelines and allows for identification of organ system functional correlations. Globally, the data support the use of social housing in non-rodents for safety pharmacology multi-organ system (heart and lungs) monitoring investigations.

Norepinephrine Protects against Methamphetamine Toxicity through ß2-Adrenergic Receptors Promoting LC3 Compartmentalization.

Norepinephrine (NE) neurons and extracellular NE exert some protective effects against a variety of insults, including methamphetamine (Meth)-induced cell damage. The intimate mechanism of protection remains difficult to be analyzed in vivo. In fact, this may occur directly on target neurons or as the indirect consequence of NE-induced alterations in the activity of trans-synaptic loops. Therefore, to elude neuronal networks, which may contribute to these effects in vivo, the present study investigates whether NE still protects when directly applied to Meth-treated PC12 cells. Meth was selected based on its detrimental effects along various specific brain areas. The study shows that NE directly protects in vitro against Meth-induced cell damage. The present study indicates that such an effect fully depends on the activation of plasma membrane ß2-adrenergic receptors (ARs). Evidence indicates that ß2-ARs activation restores autophagy, which is impaired by Meth administration. This occurs via restoration of the autophagy flux and, as assessed by ultrastructural morphometry, by preventing the dissipation of microtubule-associated protein 1 light chain 3 (LC3) from autophagy vacuoles to the cytosol, which is produced instead during Meth toxicity. These findings may have an impact in a variety of degenerative conditions characterized by NE deficiency along with autophagy impairment.

Anti-Tremor Action of Subtype Selective Positive Allosteric Modulators of GABAA Receptors in a Rat Model of Essential Tremors.

Essential tremor (ET) is among the most prevalent neurological disorders and the most common cause of abnormal tremors. It is characterized by postural and action tremors ranging from 4 to 12 Hz. The treatments of choice for ET are propranolol and primidone, but their use is associated with adverse effects like hypotension, depression, and cognitive impairments. Benzodiazepines, which nonselectively enhances the effect of GABA at the GABAA α1/2/3/5 receptors, have been shown to be effective in treating ET. Their use, however, is limited due to sedation, ataxia, tolerance development and memory impairment. Sedation and ataxia are attributed to the activity at the α1 subunit while cognitive impairment is ascribed to the action on the α5 subunit of the GABAA receptors. It can be hypothesized that subtype selective GABAA receptor modulators only acting via the α2, and α3 subunits may have an improved side effect profile while retaining the beneficial effects. Here, we have evaluated the effect of subtype selective GABAA α2/3/5 receptor modulators on harmaline-induced tremors in rats. The tremors were automatically quantified in tremor boxes. We show that the GABAA α2/3 subtype selective modulator NS16085 significantly and dose-dependently inhibits harmaline-induced tremors in rats, indicating that potentiation of α2- and α3-containing GABAA receptors is sufficient to ameliorate harmaline-induced tremors. These results provide the first support for a therapeutic role of a subtype selective GABAA α2/3 modulator in the treatment of ET.

Pramipexole Reduces zif-268 mRNA Expression in Brain Structures involved in the Generation of Harmaline-Induced Tremor.

Essential tremor is one of the most common neurological disorders, however, it is not sufficiently controlled with currently available pharmacotherapy. Our recent study has shown that pramipexole, a drug efficient in inhibiting parkinsonian tremor, reduced the harmaline-induced tremor in rats, generally accepted to be a model of essential tremor. The aim of the present study was to investigate brain targets for the tremorolytic effect of pramipexole by determination of the early activity-dependent gene zif-268 mRNA expression. Tremor in rats was induced by harmaline administered at a dose of 15 mg/kg ip. Pramipexole was administered at a low dose of 0.1 mg/kg sc. Tremor was measured by Force Plate Actimeters where four force transducers located below the corners of the plate tracked the animal's position on a Cartesian plane. The zif-268 mRNA expression was analyzed by in situ hybridization in brain slices. Harmaline induced tremor and increased zif-268 mRNA levels in the inferior olive, cerebellar cortex, ventroanterior/ventrolateral thalamic nuclei and motor cortex. Pramipexole reversed both the harmaline-induced tremor and the increase in zif-268 mRNA expression in the inferior olive, cerebellar cortex and motor cortex. Moreover, the tremor intensity correlated positively with zif-268 mRNA expression in the above structures. The present results seem to suggest that the tremorolytic effect of pramipexole is related to the modulation of the harmaline-increased neuronal activity in the tremor network which includes the inferior olive, cerebellar cortex and motor cortex. Potential mechanisms underlying the above pramipexole action are discussed.

Trait specific modulatory effects of caffeine exposure on compulsive-like behaviors in a spontaneous mouse model of obsessive-compulsive disorder.

Obsessive-compulsive disorder (OCD) is a psychiatric disorder characterized by recurring intrusive thoughts and repetitive compulsive behaviors, ultimately interfering with their quality of life. The complex heterogeneity of symptom dimensions across OCD patient subgroups impedes diagnosis and treatment. The core and comorbid symptomologies of OCD are thought to be modulated by common environmental exposures such as consumption of the psychostimulant caffeine. The effect of caffeine on the expression of obsessions and compulsions are unexplored. The current study utilized mouse strains (HA) with a spontaneous, predictable, and stable compulsive-like phenotype that have face, predictive, and construct validity for OCD. We demonstrate that an acute high dose (25 mg/kg) of caffeine decreased compulsive-like nest-building behavior in the HA strains in the first hour after injection. However, nest-building scores increased in hours 3, 4, and 5 after administration finally decreasing over a 24 h period. In contrast, a high dose of chronic caffeine (25 mg/kg/d) increased nest-building behavior. Interestingly for compulsive-like digging behavior, acute exposure to a high dose of caffeine decreased the number of marbles buried, while chronic exposure had little effect. An acute high dose of caffeine decreased anxiety-like and motor activity in open field behaviors whereas chronic caffeine administration did not have any overall effect on open field activity. The results, therefore, suggest a complex role of caffeine on compulsive-like, anxiety-like, and locomotor behaviors that is dependent on the duration of exposure.