Cocaine-induced behavioral sensitization is associated with changes in the expression of endocannabinoid and glutamatergic signaling systems in the mouse prefrontal cortex

Exploratory study on plasma Acylglycerol and Acylethanolamide dysregulation in substance use and attention-deficit/hyperactivity disorder: Implications for novel biomarkers in dual diagnosis

Substance use disorder (SUD) is a major global public health challenge, frequently co-occurring with psychiatric conditions such as attention-deficit/hyperactivity disorder (ADHD). Endocannabinoid system (ECS) dysregulation has been implicated in both SUD and ADHD, but the interplay between these conditions remains poorly understood. This study investigates plasma concentrations of endocannabinoid-congeners in individuals with SUD, with and without comorbid ADHD, to identify potential biomarkers. This exploratory study included 469 participants divided into three groups: (1) healthy controls (n = 136), (2) patients with SUD without ADHD (n = 267), and (3) patients with SUD and comorbid ADHD (n = 66). Plasma concentrations of 12 endocannabinoid-related molecules, including acylglycerols (2-AG, 2-LG, 2-OG) and acylethanolamides (AEA, DEA, DHEA, DGLEA, LEA, OEA, PEA, POEA, and SEA), were quantified using high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). A multinomial Elastic Net regression model was applied to assess their biomarker potential. Patients with SUD exhibited significantly lower plasma concentrations of 2-AG and 2-LG compared to controls, while most acylethanolamides were elevated, except for POEA and SEA. ADHD comorbidity was associated with lower concentrations of 2-AG, 2-LG, AEA, DGLEA, DHEA, and SEA, while PEA was elevated. Machine learning analysis identified AEA, OEA, PEA, and SEA as key biomarkers, achieving an accuracy of 72.1 % and an ROC-AUC of 0.77. This study suggests distinct ECS alterations in SUD and comorbid ADHD, highlighting endocannabinoid-congeners as potential biomarkers. Future research should validate these findings in larger cohorts and explore ECS-targeted therapeutic interventions for dual-diagnosis populations.

Cannabidiol and addiction

Cannabidiol (CBD) has been investigated for several therapeutic applications, having reached the clinics for the treatment of certain types of epilepsies. This chapter reviews the potential of CBD for the treatment of substance use disorders (SUD). We will present a brief introduction on SUD and current treatments. In the second part, preclinical and clinical studies with CBD are discussed, focusing on its potential therapeutic application for SUD. Next, we will consider the potential molecular mechanism of action of CBD in SUD. Finally, we will summarize the main findings and perspectives in this field. There is a lack of studies on CBD and SUD in comparison to the extensive literature investigating the use of this phytocannabinoid for other neurological and psychiatric disorders, such as epilepsy. However, the few studies available do suggest a promising role of CBD in the pharmacotherapy of SUD, particularly related to cocaine and other psychostimulant drugs.

Cocaine induces locomotor sensitization through a dopamine-dependent VTA-mPFC-FrA cortico-cortical pathway in male mice

As a central part of the mammalian brain, the prefrontal cortex (PFC) has been implicated in regulating cocaine-induced behaviors including compulsive seeking and reinstatement. Although dysfunction of the PFC has been reported in animal and human users with chronic cocaine abuse, less is known about how the PFC is involved in cocaine-induced behaviors. By using two-photon Ca²⁺ imaging to simultaneously record tens of intact individual networking neurons in the frontal association cortex (FrA) in awake male mice, here we report that a systematic acute cocaine exposure decreased the FrA neural activity in mice, while the chemogenetic intervention blocked the cocaine-induced locomotor sensitization. The hypoactivity of FrA neurons was critically dependent on both dopamine transporters and dopamine transmission in the ventromedial PFC (vmPFC). Both dopamine D1R and D2R neurons in the vmPFC projected to and innervated FrA neurons, the manipulation of which changed the cocaine-induced hypoactivity of the FrA and locomotor sensitization. Together, this work demonstrates acute cocaine-induced hypoactivity of FrA neurons in awake mice, which defines a cortico-cortical projection bridging dopamine transmission and cocaine sensitization.

Identification of miRNA-mediated gene regulatory networks in L-methionine exposure counteracts cocaine-conditioned place preference in mice

Background and Aims: Methionine has been proven to inhibit addictive behaviors of cocaine dependence. This study aimed to identify the potential mechanisms of MET relating to its inhibitory effects on cocaine induced cellular and behavioral changes. Methods: MRNA and miRNA high-throughput sequencing of the prefrontal cortex in a mouse model of cocaine conditioned place preference (CPP) combined with L-methionine was performed. Differentially expressed miRNAs (DE-miRNAs) and differentially expressed genes (DEGs) regulated by cocaine and inhibited by L-methionine were identified. DEGs were mapped to STRING database to construct a protein-protein interaction (PPI) network. Then, the identified DEGs were subjected to the DAVID webserver for functional annotation. Finally, miRNA-mRNA regulatory network and miRNA-mRNA-TF regulatory networks were established to screen key DE-miRNAs and coregulation network in Cytoscape. Results: Sequencing data analysis showed that L-methionine reversely regulated genes and miRNAs affected by cocaine. Pathways associated with drug addiction only enriched in CS-down with MC-up genes targeted by DE-miRNAs including GABAergic synapse, Glutamatergic synapse, Circadian entrainment, Axon guidance and Calcium signaling pathway. Drug addiction associated network was formed of 22 DEGs including calcium channel (Cacna1c, Cacna1e, Cacna1g and Cacng8), ephrin receptor genes (Ephb6 and Epha8) and ryanodine receptor genes (Ryr1 and Ryr2). Calcium channel gene network were identified as a core gene network modulated by L-methionine in response to cocaine dependence. Moreover, it was predicted that Grin1 and Fosb presented in TF-miRNA-mRNA coregulation network with a high degree of interaction as hub genes and interacted calcium channels. Conclusion: These identified key genes, miRNA and coregulation network demonstrated the efficacy of L-methionine in counteracting the effects of cocaine CPP. To a certain degree, it may provide some hints to better understand the underlying mechanism on L-methionine in response to cocaine abuse.

Hippocampal Cannabinoid 1 Receptors Are Modulated Following Cocaine Self-administration in Male Rats

Cocaine addiction is a complex pathology inducing long-term neuroplastic changes that, in turn, contribute to maladaptive behaviors. This behavioral dysregulation is associated with transcriptional reprogramming in brain reward circuitry, although the mechanisms underlying this modulation remain poorly understood. The endogenous cannabinoid system may play a role in this process in that cannabinoid mechanisms modulate drug reward and contribute to cocaine-induced neural adaptations. In this study, we investigated whether cocaine self-administration induces long-term adaptations, including transcriptional modifications and associated epigenetic processes. We first examined endocannabinoid gene expression in reward-related brain regions of the rat following self-administered (0.33 mg/kg intravenous, FR1, 10 days) cocaine injections. Interestingly, we found increased Cnr1 expression in several structures, including prefrontal cortex, nucleus accumbens, dorsal striatum, hippocampus, habenula, amygdala, lateral hypothalamus, ventral tegmental area, and rostromedial tegmental nucleus, with most pronounced effects in the hippocampus. Endocannabinoid levels, measured by mass spectrometry, were also altered in this structure. Chromatin immunoprecipitation followed by qPCR in the hippocampus revealed that two activating histone marks, H3K4Me3 and H3K27Ac, were enriched at specific endocannabinoid genes following cocaine intake. Targeting CB1 receptors using chromosome conformation capture, we highlighted spatial chromatin re-organization in the hippocampus, as well as in the nucleus accumbens, suggesting that destabilization of the chromatin may contribute to neuronal responses to cocaine. Overall, our results highlight a key role for the hippocampus in cocaine-induced plasticity and broaden the understanding of neuronal alterations associated with endocannabinoid signaling. The latter suggests that epigenetic modifications contribute to maladaptive behaviors associated with chronic drug use.

Persistent changes in exploration and hyperactivity coexist with cognitive impairment in mice withdrawn from chronic cocaine

Repeated cocaine exposure induces lasting neurobehavioral adaptations such as cognitive decline in animal models. However, persistent changes in spontaneous -unconditioned- motor and exploratory responses are scarcely reported. In this study, mice were administered with cocaine (20 mg/kg/day) or vehicle for 12 consecutive days. After 24 days of drug abstinence, a behavioral assessment was carried out in drug-free conditions and in unfamiliar environments (i.e. no cocaine-associated cues were presented). The cocaine-withdrawn mice showed cognitive deficits in spontaneous alternation behavior and place recognition memory. Importantly, they also displayed hyperlocomotion, increased rearing activity and altered exploratory patterns in different tasks. In the forced swimming test, they were more active (struggled/climbed more) when trying to escape from the water albeit showing normal immobility behavior. In conclusion, in addition to cognitive deficits, chronic cocaine in rodents may induce long-lasting alterations in exploratory activity and psychomotor activation that are triggered even in absence of drug-related stimuli.

Therapeutic effects of astragaloside IV and Astragalus spinosus saponins against bisphenol A-induced neurotoxicity and DNA damage in rats

Background

Bisphenol A (BPA) is an endocrine disruptor to which humans are often subjected during daily life. This study aimed to investigate the ameliorative effect of astragaloside IV (ASIV) or saponins extracted from Astragalus spinosus (A. spinosus) against DNA damage and neurotoxic effects induced by BPA in prefrontal cortex (PFC), hippocampal and striatal brain regions of developing male rats.

Materials and Methods

Juvenile PND20 (pre-weaning; age of 20 days) male Sprague Dawley rats were randomly and equally divided into four groups: control, BPA, BPA+ASIV and BPA+A. spinosus saponins groups. Bisphenol A (125 mg/kg/day) was administrated orally to male rats from day 20 (BPA group) and along with ASIV (80 mg/kg/day) (BPA+ASIV group) or A. spinosus saponin (100 mg/kg/day) (BPA+ A. spinosus saponins group) from day 50 to adult age day 117.

Results

Increased level of nitric oxide (NO) and decreased level of glutamate (Glu), glutamine (Gln), glutaminase (GA) and glutamine synthetase (GS) were observed in the brain regions of BPA treated rats compared with the control. On the other hand, co-administration of ASIV or A. spinosus saponin with BPA considerably improved levels of these neurochemicals. The current study also revealed restoration of the level of brain derived neurotrophic factor (BDNF) and N-methyl-D-aspartate receptors (NR₂A and NR₂B) gene expression in BPA+ ASIV and BPA+A. spinosus saponins groups. The co-treatment of BPA group with ASIV or A. spinosus saponin significantly reduced the values of comet parameters as well as the intensity of estrogen receptors (ERs) immunoreactive cells and improved the histological alterations induced by BPA in different brain regions.

Conclusion

It could be concluded that ASIV or A. spinosus saponins has a promising role in modulating the neurotoxicity and DNA damage elicited by BPA.

Endocannabinoid signaling regulates the reinforcing and psychostimulant effects of ketamine in mice

The abuse potential of ketamine limits its clinical application, but the precise mechanism remains largely unclear. Here we discovered that ketamine significantly remodels the endocannabinoid-related lipidome and activates 2-arachidonoylglycerol (2-AG) signaling in the dorsal striatum (caudate nucleus and putamen, CPu) of mice. Elevated 2-AG in the CPu is essential for the psychostimulant and reinforcing effects of ketamine, whereas blockade of the cannabinoid CB1 receptor, a predominant 2-AG receptor, attenuates ketamine-induced remodeling of neuronal dendrite structure and neurobehaviors. Ketamine represses the transcription of the monoacylglycerol lipase (MAGL) gene by promoting the expression of PRDM5, a negative transcription factor of the MAGL gene, leading to increased 2-AG production. Genetic overexpression of MAGL or silencing of PRDM5 expression in the CPu robustly reduces 2-AG production and ketamine effects. Collectively, endocannabinoid signaling plays a critical role in mediating the psychostimulant and reinforcing properties of ketamine.

Cocaine-induced Changes in the Expression of NMDA Receptor Subunits

Cocaine use disorder is manifested by repeated cycles of drug seeking and drug taking. Cocaine exposure causes synaptic transmission in the brain to exhibit persistent changes, which are poorly understood, while the pharmacotherapy of this disease has not been determined. Multiple potential mechanisms have been indicated to be involved in the etiology of co-caine use disorder. The glutamatergic system, especially N-methyl-D-aspartate (NMDA) receptors, may play a role in sever-al physiological processes (synaptic plasticity, learning and memory) and in the pathogenesis of cocaine use disorder. The composition of the NMDA receptor subunits changes after contingent and noncontingent cocaine administration and after drug abstinence in a region-specific and time-dependent manner, as well as depending on the different protocols used for co-caine administration. Changes in the expression of NMDA receptor subunits may underlie the transition from cocaine abuse to dependence, as well as the transition from cocaine dependence to cocaine withdrawal. In this paper, we summarize the cur-rent knowledge regarding neuroadaptations within NMDA receptor subunits and scaffolding proteins observed following voluntary and passive cocaine intake, as well as the effects of NMDA receptor antagonists on cocaine-induced behavioral changes during cocaine seeking and relapse.

FAAH levels and its genetic polymorphism association with susceptibility to methamphetamine dependence

The fatty acid amide hydrolase (FAAH) gene was involved in the modulation of reward and addiction pathophysiology of illicit drugs abuse, and its polymorphisms might be associated with risk of methamphetamine (METH) dependence. This study aimed to investigate the FAAH mRNA levels in peripheral blood mononuclear cells and plasma protein levels and to analyze the 385C/A polymorphism (rs324420) between METH-dependent patients and controls. The levels of FAAH mRNA in METH dependence were significantly lower than in controls (P < 0.001), however, its plasma protein underwent a significant ∼2-fold increase (P < 0.001). The A allele of the 385C/A polymorphism significantly increased the METH dependence risk (P < 0.001, odds ratio [OR] = 1.646, 95% confidence interval [CI] = 1.332-2.034). The carried A genotypes (AA, AC, and AA/AC) of 385C/A polymorphism also increased METH-dependence risks under a different genetic model (AA vs. CC: P = 0.017, OR = 2.454, 95%CI = 1.171-2.143; AC vs. CC: P < 0.001, OR = 1.818, 95%CI = 1.404-2.353; AC/AA vs. CC: P < 0.001, OR = 1.858, 95%CI = 1.444-2.319). The similar results were obtained after adjusting for age and sex. Unfortunately, we failed to find that any genotype of 385C/A polymorphism affected the mRNA or plasma protein levels in controls, respectively (P > 0.05). These data indicate that the FAAH may play an important role in the pathophysiological process of METH dependence, and the 385C/A polymorphism may be associated with METH dependence susceptibility in a Chinese Han population.

Potential of Cannabinoid Receptor Ligands as Treatment for Substance Use Disorders

Substance use disorder (SUD) is a major public health crisis worldwide, and effective treatment options are limited. During the past 2 decades, researchers have investigated the impact of a variety of pharmacological approaches to treat SUD, one of which is the use of medical cannabis or cannabinoids. Significant progress was made with the discovery of rimonabant, a selective CB1 receptor (CB1R) antagonist (also an inverse agonist), as a promising therapeutic for SUDs and obesity. However, serious adverse effects such as depression and suicidality led to the withdrawal of rimonabant (and almost all other CB1R antagonists/inverse agonists) from clinical trials worldwide in 2008. Since then, much research interest has shifted to other cannabinoid-based strategies, such as peripheral CB1R antagonists/inverse agonists, neutral CB1R antagonists, allosteric CB1R modulators, CB2R agonists, fatty acid amide hydrolase (FAAH) inhibitors, monoacylglycerol lipase (MAGL) inhibitors, fatty acid binding protein (FABP) inhibitors, or nonaddictive phytocannabinoids with CB1R or CB2R-binding profiles, as new therapeutics for SUDs. In this article, we first review recent progress in research regarding the endocannabinoid systems, cannabis reward versus aversion, and the underlying receptor mechanisms. We then review recent progress in cannabinoid-based medication development for the treatment of SUDs. As evidence continues to accumulate, neutral CB1R antagonists (such as AM4113), CB2R agonists (JWH133, Xie2-64), and nonselective phytocannabinoids (cannabidiol, β-caryophyllene, ∆9-tetrahydrocannabivarin) have shown great therapeutic potential for SUDs, as shown in experimental animals. Several cannabinoid-based medications (e.g., dronabinol, nabilone, PF-04457845) that entered clinical trials have shown promising results in reducing withdrawal symptoms in cannabis and opioid users.

Amphetamine-induced Conditioned Place Preference and Changes in mGlu1/5 Receptor Expression and Signaling in the Rat Medial Prefrontal Cortex

The medial prefrontal cortex (mPFC) is implicated in the rewarding effect of psychostimulants, although molecular mechanisms underlying the rewarding properties of stimulants in this region are poorly understood. Group I metabotropic glutamate (mGlu) receptors (mGlu1/5 subtypes) are believed to be critical in this event. We thus in this study investigated changes in mGlu1/5 receptor expression and function in the rat mPFC in response to conditioned place preference (CPP) induced by amphetamine. Repeated amphetamine administration (2.5 mg/kg, once daily on alternate days for 10 days) induced reliable CPP. In the mPFC, surface expression of mGlu5 receptors was elevated in rats after amphetamine conditioning. mGlu5 receptors were also increased at synaptic and extrasynaptic sites in amphetamine-conditioned rats. Expression of mGlu1 receptors was stable in surface and synaptic compartments, while it was elevated in the extrasynaptic location. In mPFC neurons, the mGlu1/5 agonist-stimulated phosphoinositide signaling pathway was upregulated in its efficacy following amphetamine conditioning. The mGlu1/5 agonist-stimulated Src kinase phosphorylation was also augmented in rats treated with amphetamine. These results demonstrate the sensitivity of mPFC mGlu1/5 receptors to amphetamine-induced CPP. Amphetamine conditioning results in the upregulation of mGlu1/5 receptor expression at subcellular and/or subsynaptic levels and mGlu1/5-mediated postreceptor signaling in mPFC neurons.

Interaction Between Stress and Addiction: Contributions From Latin-American Neuroscience

Drug addiction is a chronic neuropsychiatric disorder that escalates from an initial exposure to drugs of abuse, such as cocaine, cannabis, or heroin, to compulsive drug-seeking and intake, reduced ability to inhibit craving-induced behaviors, and repeated cycles of abstinence and relapse. It is well-known that chronic changes in the brain’s reward system play an important role in the neurobiology of addiction. Notably, environmental factors such as acute or chronic stress affect this system, and increase the risk for drug consumption and relapse. Indeed, the HPA axis, the autonomic nervous system, and the extended amygdala, among other brain stress systems, interact with the brain’s reward circuit involved in addictive behaviors. There has been a growing interest in studying the molecular, cellular, and behavioral mechanisms of stress and addiction in Latin-America over the last decade. Nonetheless, these contributions may not be as strongly acknowledged by the broad scientific audience as studies coming from developed countries. In this review, we compile for the first time a series of studies conducted by Latin American-based neuroscientists, who have devoted their careers to studying the interaction between stress and addiction, from a neurobiological and clinical perspective. Specific contributions about this interaction include the study of CRF receptors in the lateral septum, investigations on the neural mechanisms of cross-sensitization for psychostimulants and ethanol, the identification of the Wnt/β-catenin pathway as a critical neural substrate for stress and addiction, and the emergence of the cannabinoid system as a promising therapeutic target. We highlight animal and human studies, including for instance, reports coming from Latin American laboratories on single nucleotide polymorphisms in stress-related genes and potential biomarkers of vulnerability to addiction, that aim to bridge the knowledge from basic science to clinical research.

Contributions of prolonged contingent and non-contingent cocaine exposure to escalation of cocaine intake and glutamatergic gene expression

Similar to the pattern observed in people with substance abuse disorders, laboratory animals will exhibit escalation of cocaine intake when the drug is available over prolonged periods of time. Here, we investigated the contribution of behavioral contingency of cocaine administration on escalation of cocaine intake and gene expression in the dorsal medial prefrontal cortex (dmPFC) in adult male rats. Rats were allowed to self-administer intravenous cocaine (0.25 mg/infusion) under either limited cocaine-(1 h/day), prolonged cocaine-(6 h/day), or limited cocaine-(1 h/day) plus yoked cocaine-access (5 h/day); a control group received access to saline (1 h/day). One day after the final self-administration session, the rats were euthanized and the dmPFC was removed for quantification of mRNA expression of critical glutamatergic signaling genes, Homer2, Grin1, and Dlg4, as these genes and brain region have been previously implicated in addiction, learning, and memory. All groups with cocaine-access showed escalated cocaine intake during the first 10 min of each daily session, and within the first 1 h of cocaine administration. Additionally, the limited-access + yoked group exhibited more non-reinforced lever responses during self-administration sessions than the other groups tested. Lastly, Homer2, Grin1, and Dlg4 mRNA were impacted by both duration and mode of cocaine exposure. Only prolonged-access rats exhibited increases in mRNA expression for Homer2, Grin1, and Dlg4 mRNA. Taken together, these findings indicate that both contingent and non-contingent "excessive" cocaine exposure supports escalation behavior, but the behavioral contingency of cocaine-access has distinct effects on the patterning of operant responsiveness and changes in mRNA expression.

The acute effect of cannabis on plasma, liver and brain ammonia dynamics, a translational study

Recent reports of ammonia released during cannabis smoking raise concerns about putative neurotoxic effects. Cannabis (54mg) was administered in a double-blind, placebo-controlled design to healthy cannabis users (n=15) either orally, or through smoking (6.9%THC cigarette) or inhalation of vaporized cannabis (Volcano®). Serial assay of plasma ammonia concentrations at 0, 2, 4, 6, 8, 10, 15, 30, and 90min from onset of cannabis administration showed significant time (P=0.016), and treatment (P=0.0004) effects with robust differences between placebo and edible at 30 (P=0.002), and 90min (P=0.007) and between placebo and vaporized (P=0.02) and smoking routes (P=0.01) at 90min. Furthermore, plasma ammonia positively correlated with blood THC concentrations (P=0.03). To test the hypothesis that this delayed increase in plasma ammonia originates from the brain we administered THC (3 and 10mg/kg) to mice and measured plasma, liver, and brain ammonia concentrations at 1, 3, 5 and 30min post-injection. Administration of THC to mice did not cause significant change in plasma ammonia concentrations within the first 5min, but significantly reduced striatal glutamine-synthetase (GS) activity (P=0.046) and increased striatal ammonia concentration (P=0.016). Furthermore, plasma THC correlated positively with striatal ammonia concentration (P<0.001) and negatively with striatal GS activity (P=0.030). At 30min, we found marked increase in striatal ammonia (P<0.0001) associated with significant increase in plasma ammonia (P=0.042) concentration. In conclusion, the results of these studies demonstrate that cannabis intake caused time and route-dependent increases in plasma ammonia concentrations in human cannabis users and reduced brain GS activity and increased brain and plasma ammonia concentrations in mice.

Presynaptic G Protein-Coupled Receptors: Gatekeepers of Addiction?

Drug abuse and addiction cause widespread social and public health problems, and the neurobiology underlying drug actions and drug use and abuse is an area of intensive research. Drugs of abuse alter synaptic transmission, and these actions contribute to acute intoxication as well as the chronic effects of abused substances. Transmission at most mammalian synapses involves neurotransmitter activation of two receptor subtypes, ligand-gated ion channels that mediate fast synaptic responses and G protein-coupled receptors (GPCRs) that have slower neuromodulatory actions. The GPCRs represent a large proportion of neurotransmitter receptors involved in almost all facets of nervous system function. In addition, these receptors are targets for many pharmacotherapeutic agents. Drugs of abuse directly or indirectly affect neuromodulation mediated by GPCRs, with important consequences for intoxication, drug taking and responses to prolonged drug exposure, withdrawal and addiction. Among the GPCRs are several subtypes involved in presynaptic inhibition, most of which are coupled to the Gi/o class of G protein. There is increasing evidence that these presynaptic Gi/o-coupled GPCRs have important roles in the actions of drugs of abuse, as well as behaviors related to these drugs. This topic will be reviewed, with particular emphasis on receptors for three neurotransmitters, Dopamine (DA; D1- and D2-like receptors), Endocannabinoids (eCBs; CB1 receptors) and glutamate (group II metabotropic glutamate (mGlu) receptors). The focus is on recent evidence from laboratory animal models (and some evidence in humans) implicating these receptors in the acute and chronic effects of numerous abused drugs, as well as in the control of drug seeking and taking. The ability of drugs targeting these receptors to modify drug seeking behavior has raised the possibility of using compounds targeting these receptors for addiction pharmacotherapy. This topic is also discussed, with emphasis on development of mGlu2 positive allosteric modulators (PAMs).

Changes in CREB and deltaFosB are associated with the behavioural sensitization induced by methylenedioxypyrovalerone

Methylenedioxypyrovalerone (MDPV) is a synthetic cathinone which has recently emerged as a designer drug of abuse. The objective of this study was to investigate the locomotor sensitization induced by MDPV in adolescent mice, and associated neuroplastic changes in the nucleus accumbens and striatum through deltaFosB and CREB expression. Behavioural testing consisted of three phases: Phase I: conditioning regimen with MDPV (0.3 mg/kg/day for five days) or saline; Phase II: resting (11 days); Phase III: challenged with MDPV (0.3 mg/kg), cocaine (10 mg/kg) or saline on day 16 for both groups. Mice repeatedly exposed to MDPV increased locomotor activity by 165-200% following acute MDPV or cocaine administration after an 11-day resting period, showing a MDPV-induced sensitization to itself and to cocaine. An explanation for this phenomenon could be the common mechanism of action between these two psychostimulants. Furthermore, the MDPV challenge resulted in higher levels of phospho-CREB in MDPV-conditioned mice compared with MDPV-naive mice, probably due to an up-regulation of the cAMP pathway. Likewise, MDPV exposure induced a persistent increase in the striatal expression of deltaFosB; the priming dose of MDPV also produced a significant increase in the accumbal expression of this transcription factor. This study constitutes the first evidence that an exposure to a low dose of MDPV during adolescence induces behavioural sensitization and provides a neurobiological basis for a relationship between MDPV and cocaine. We hypothesize that, similar to cocaine, both CREB and deltaFosB play a role in the induction of this behavioural sensitization.

Beyond the CB1 Receptor: Is Cannabidiol the Answer for Disorders of Motivation?

The Cannabis sativa plant has been used to treat various physiological and psychiatric conditions for millennia. Current research is focused on isolating potentially therapeutic chemical constituents from the plant for use in the treatment of many central nervous system disorders. Of particular interest is the primary nonpsychoactive constituent cannabidiol (CBD). Unlike Δ(9)-tetrahydrocannabinol (THC), CBD does not act through the cannabinoid type 1 (CB1) receptor but has many other receptor targets that may play a role in psychiatric disorders. Here we review preclinical and clinical data outlining the therapeutic efficacy of CBD for the treatment of motivational disorders such as drug addiction, anxiety, and depression. Across studies, findings suggest promising treatment effects and potentially overlapping mechanisms of action for CBD in these disorders and indicate the need for further systematic investigation of the viability of CBD as a psychiatric pharmacotherapy.

To Act or Not to Act: Endocannabinoid/Dopamine Interactions in Decision-Making

Decision-making is an ethologically adaptive construct that is impaired in multiple psychiatric disorders. Activity within the mesocorticolimbic dopamine system has been traditionally associated with decision-making. The endocannabinoid system through its actions on inhibitory and excitatory synapses modulates dopamine activity and decision-making. The aim of this brief review is to present a synopsis of available data obtained when the endocannabinoid system is manipulated and dopamine activity recorded. To this end, we review research using different behavioral paradigms to provide further insight into how this ubiquitous signaling system biases dopamine-related behaviors to regulate decision-making.

3'-Deoxyadenosine (Cordycepin) Produces a Rapid and Robust Antidepressant Effect via Enhancing Prefrontal AMPA Receptor Signaling Pathway

BACKGROUND

The development of rapid and safe antidepressants for the treatment of major depression is in urgent demand. Converging evidence suggests that glutamatergic signaling seems to play important roles in the pathophysiology of depression.

METHODS

We studied the antidepressant effects of 3(')-deoxyadenosine (3'-dA, Cordycepin) and the critical role of the α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor in male CD-1 mice via behavioral and biochemical experiments. After 3'-dA treatment, the phosphorylation and synaptic localization of the AMPA receptors GluR1 and GluR2 were determined in the prefrontal cortex (PFC) and hippocampus (HIP). The traditional antidepressant imipramine was applied as a positive control.

RESULTS

We found that an injection of 3'-dA led to a rapid and robust antidepressant effect, which was significantly faster and stronger than imipramine, after 45min in tail suspension and forced swim tests. This antidepressant effect remained after 5 days of treatment with 3'-dA. Unlike the psycho-stimulants, 3'-dA did not show a hyperactive effect in the open field test. After 45min or 5 days of treatment, 3'-dA enhanced GluR1 S845 phosphorylation in both the PFC and HIP. In addition, after 45min of treatment, 3'-dA significantly up-regulated GluR1 S845 phosphorylation and GluR1, but not GluR2 levels, at the synapses in the PFC. After 5 days of treatment, 3'-dA significantly enhanced GluR1 S845 phosphorylation and GluR1, but not GluR2, at the synapses in the PFC and HIP. Moreover, the AMPA-specific antagonist GYKI 52466 was able to block the rapid antidepressant effects of 3'-dA.

CONCLUSION

This study identified 3'-dA as a novel rapid antidepressant with clinical potential and multiple beneficial mechanisms, particularly in regulating the prefrontal AMPA receptor signaling pathway.