Cocaine Exposure Research Articles

Astrocytic Regulation of Cocaine Locomotor Sensitization in EcoHIV Infected Mice

Cocaine use disorder (CUD) is highly comorbid with HIV infection and worsens HIV outcomes. Preclinical research on the outcomes of HIV infection may yield crucial information on neurobehavioral changes resulting from chronic drug exposure in people living with HIV (PLWH). Repeated exposure to cocaine alters behavioral responses to cocaine. This includes development of cocaine locomotor sensitization - or increased locomotor responses to the same doses of cocaine - which depends on nucleus accumbens (NAc) neural plasticity. NAc astrocytes are key regulators of neural activity and plasticity, and their function can be impaired by cocaine exposure and HIV infection, thus implicating them as potential regulators of HIV-induced changes in behavioral response to cocaine. To characterize the effects of HIV infection on cocaine locomotor sensitization, we employed the EcoHIV mouse model in male and female mice to assess changes in locomotor responses after repeated cocaine (10mg/kg) exposure and challenge. EcoHIV infection potentiated expression of cocaine sensitization. We also identified EcoHIV-induced increases in expression of the astrocytic nuclear marker Sox9 selectively in the NAc core. To investigate whether modulation of NAc astrocytes could reverse EcoHIV-induced deficits, we employed a chemogenetic approach. We found that chemogenetic activation of NAc astrocyte Gq signaling attenuated EcoHIV-enhanced cocaine sensitization. We propose that HIV infection contributes to cocaine behavioral sensitization and induces adaptations in NAc astrocytes, while promoting NAc astrocytic Gq-signaling can recover EcoHIV-induced behavioral changes. These findings identify potential cellular substrates of disordered cocaine-driven behavior in the context of HIV infection and point toward strategies to reduce cocaine-related behavior in PLWH.

Cocaine-Induced DNA-Dependent Protein Kinase Relieves RNAP II Pausing by Promoting TRIM28 Phosphorylation and RNAP II Hyperphosphorylation to Enhance HIV Transcription

Drug abuse continues to pose a significant challenge in HIV control efforts. In our investigation, we discovered that cocaine not only upregulates the expression of the DNA-dependent protein kinase (DNA-PK) but also augments DNA-PK activation by enhancing its phosphorylation at S2056. Moreover, DNA-PK phosphorylation triggers the higher localization of the DNA-PK into the nucleus. The finding that cocaine increases the nuclear localization of the DNA-PK provides further support to our observation of enhanced DNA-PK recruitment at the HIV long terminal repeat (LTR) following cocaine exposure. By activating and facilitating the nuclear localization of the DNA-PK, cocaine effectively orchestrates multiple stages of HIV transcription, thereby promoting HIV replication. Additionally, our study demonstrates that the cocaine-induced DNA-PK promotes the hyper-phosphorylation of the RNA polymerase II (RNAP II) carboxyl-terminal domain (CTD) at Ser5 and Ser2 sites, enhancing both the initiation and elongation phases, respectively, of HIV transcription. The cocaine-mediated enhancement of transcriptional initiation is supported by its activation of cyclin-dependent kinase 7 (CDK7). Additionally, the induction of transcriptional elongation is marked by higher LTR recruitment and the increased phosphorylation of CDK9, which indicates the stimulation of positive transcriptional elongation factor b (P-TEFb). We demonstrate for the first time that cocaine, through DNA-PK activation, promotes the specific phosphorylation of TRIM28 at serine 824 (p-TRIM28, S824). This modification converts TRIM28 from a transcriptional inhibitor to a transactivator for HIV transcription. Additionally, we observed that the phosphorylation of TRIM28 (p-TRIM28, S824) promotes the transition from the pausing phase to the elongation phase of HIV transcription, thereby facilitating the production of full-length HIV genomic transcripts. This finding corroborates the previously observed enhanced RNAP II CTD phosphorylation at Ser2, a marker of transcriptional elongation, following cocaine exposure. Accordingly, upon cocaine treatment, we observed the elevated recruitment of p-TRIM28-(S824) at the HIV LTR. Overall, our results unravel the intricate molecular mechanisms underlying cocaine-induced HIV transcription and gene expression. These findings hold promise for the development of highly targeted therapeutics aimed at mitigating the detrimental effects of cocaine in individuals living with HIV.

Neuroplasticity and Cocaine Exposure During Adolescence

The adolescent brain is particularly vulnerable to the effects of cocaine exposure due to ongoing neurodevelopment especially in areas that are crucial for cognitive and emotional regulation. This review explores the multifaceted impact of cocaine on neuroplasticity during adolescence, thereby highlighting both the immediate and long-term consequences of drug exposure. Key findings from recent studies indicate that cocaine use during adolescence leads to significant alterations in synaptic plasticity, dendritic spine morphology, and neurotransmitter systems, which may persist into adulthood and contribute to addictive behaviors. Additionally, the interaction between genetic predispositions, environmental stressors, and drug exposure is emphasized. The review also analyzed the risks of early-life stress and social isolation on cocaine-induced neuroplasticity, which can render anxiety-related behaviors and lead to neurological changes. Future studies should incorporate longitudinal design to understand the long-term trajectory of neuroplasticity induced by cocaine. This paper can provide some suggestions to the development of prevention and intervention programs for adolescents at risk.

Cell type-specific epigenetic priming of gene expression in nucleus accumbens by cocaine.

A hallmark of addiction is the ability of drugs of abuse to trigger relapse after periods of prolonged abstinence. Here, we describe an epigenetic mechanism whereby chronic cocaine exposure causes lasting chromatin and downstream transcriptional modifications in the nucleus accumbens (NAc), a critical brain region controlling motivation. We link prolonged withdrawal from cocaine to the depletion of the histone variant H2A.Z, coupled with increased genome accessibility and latent priming of gene transcription, in D1 dopamine receptor-expressing medium spiny neurons (D1 MSNs) that relate to aberrant gene expression upon drug relapse. The histone chaperone ANP32E removes H2A.Z from chromatin, and we demonstrate that D1 MSN-selective Anp32e knockdown prevents cocaine-induced H2A.Z depletion and blocks cocaine's rewarding actions. By contrast, very different effects of cocaine exposure, withdrawal, and relapse were found for D2 MSNs. These findings establish histone variant exchange as an important mechanism and clinical target engaged by drugs of abuse to corrupt brain function and behavior.

B-274 Determining Novel Biomarker Candidates Associated With Heroin and Cocaine Exposure Using Urine Metabolomics

Abstract Background Substance abuse poses an escalating health risk in the United States. While acute drug exposure can be tracked using drugs and their metabolites as biomarkers in clinical settings, there is a notable absence of biomarkers for chronic drug exposure or addiction. The development and availability of such biomarkers could significantly enhance clinicians’ ability to identify patients at high risk of addiction, and more accurately predict disease progression and treatment responses. Methods Our study aimed to discover novel biomarkers associated with substance abuse by analyzing raw mass spectrometry (MS) data from urine comprehensive drug screening (UCDS) conducted at the University of Pittsburgh Medical Center (UPMC). The MS data, acquired through untargeted data collection using LC-qToF-MS at the UPMC Clinical Toxicology Laboratory, was initially preprocessed (including peak identification, alignment, and putative annotation) using MS-DIAL to generate a data matrix. This matrix, consisting of objects (cases) and features (m/z and retention time), was further normalized and analyzed using MetaboAnalyst. A combination of statistical methods, including point biserial correlation analysis, volcano plot, significance analysis of microarrays and metabolites (SAM), empirical Bayesian analysis of microarrays and metabolites (EBAM), partial least squares discriminant analysis (PLS-DA), and random forest (RF), were employed to select features significantly associated with the EIA-results. These features were subsequently evaluated for analyte identification using MS-FINDER. Results Our analysis identified nine significant features associated with 6MAM-EIA for heroin abuse, including 6-monoacetylmorphine itself and norfentanyl. For features associated with cocaine metabolite-EIA, 37 significant features were selected, including multiple cocaine metabolites, nicotine metabolites, and norfentanyl. Some of these selected features are likely products of in-source fragmentation or endogenous metabolites. Conclusions Our study has identified a set of potential biomarker candidates for illicit drug exposure. Notably, norfentanyl was found to be significantly associated with both 6MAM-EIA and cocaine metabolite-EIA, reflecting current trends in illicit drug use. Further chemical identification of these biomarkers is planned for future work.

Effects of prenatal cocaine exposure on estrous cycle, and behavior and expression of estrogen receptor alpha and oxytocin during estrus and diestrus in mice offspring.

Increasing evidence indicates that prenatal cocaine exposure may result in many developmental and long-lasting neurological and behavioral effects. The behaviors of female animals are strongly associated with the estrous cycle. Estrogen receptors and oxytocin are important neuroendocrine factors that regulate social behavior and are of special relevance to females. However, whether prenatal cocaine exposure induces estrous cycle changes in offspring and whether neurobehavioral changes in estrus and diestrus offspring differ remains unclear. On gestational day 12, mice were administered cocaine once daily for seven consecutive days, then the estrous cycle was examined in adult female offspring, as well as locomotion, anxiety level, and social behaviors, and the expression of estrogen receptor alpha-immunoreactive and oxytocin-immunoreactive neurons were compared between estrus and diestrus offspring. Prenatal cocaine exposure resulted in the shortening of proestrus and estrus in the offspring. During estrus and diestrus, prenatally cocaine-exposed offspring showed increased anxiety levels and changed partial social behaviors; their motility showed no significant differences in estrus, but declined in diestrus. Prenatal cocaine exposure reduced estrogen receptor alpha-immunoreactive expression in the medial preoptic area, ventromedial hypothalamic nucleus, and arcuate nucleus and oxytocin-immunoreactive expression in the paraventricular nucleus in estrus and diestrus offspring. These results suggest that prenatal cocaine exposure induces changes in the offspring's estrous cycle and expression of estrogen receptor alpha and oxytocin in a brain region-specific manner and that prenatal cocaine exposure and the estrous cycle interactively change motility and partial social behavior. Estrogen receptor alpha and oxytocin signaling are likely to play important concerted roles in mediating the effects of prenatal cocaine exposure on the offspring.

Prenatal and postnatal cocaine exposure enhances the anxiety- and depressive-like behaviors in rats: An ontogenetic study.

Prenatal and postnatal exposure to drugs such as cocaine is a public health problem that causes deficits in brain development and function in humans and animals. One of the main effects of prenatal and postnatal cocaine exposure is increased vulnerability to developing the substance use disorder at an early age. Furthermore, the negative emotional states associated with cocaine withdrawal increase the fragility of patients to relapse into drug abuse. In this sense, prenatal and postnatal cocaine exposure enhanced the cocaine- and nicotine-induced locomotor activity and locomotor sensitization, and rats exposed prenatally to cocaine displayed an increase in anxiety- and depressive-like behaviors in adulthood (PND 60-70). Therefore, the objective of this study was to determine the effect of prenatal and postnatal cocaine exposure on anxiety- and depressive-like behaviors at different ages (30, 60, 90, and 120 days of age) in rats. The study was divided into two stages: prenatal and postnatal. In the prenatal stage, a group of pregnant female Wistar rats was administered daily from GD0 to GD21 cocaine (cocaine pre-exposure group), and another group of pregnant female rats was administered daily saline (saline pre-exposure group). In the postnatal stage, during lactation (PND0 to PND21), pregnant rats received administration of cocaine or saline, respectively. Of the litters resulting from the cocaine pre-exposed and saline pre-exposed pregnant female groups, only the male rats were used for the recording of the anxiety- and depressive-like behaviors at different postnatal ages (30, 60, 90, and 120 days), representative of adolescence, adult, adulthood, and old age. The study found that prenatal and postnatal cocaine exposure generated age-dependent enhancement in anxiety- and depressive-like behaviors, being greater in older adult (PND 120) rats than in adolescent (PND 30) or adults (PND 60-90) rats. This suggests that prenatal and postnatal cocaine exposure increases anxiety- and depressive-like behaviors, which may increase the vulnerability of subjects to different types of drugs in young and adult age.

The effects of amphetamine exposure on stress susceptibility in mice

Substance use disorders (SUDs) and their many psychiatric comorbidities, including major depression and anxiety disorders, are characterized by significant sex differences. Although the causes of SUDs and their psychiatric comorbidities remain unknown, stress has been heavily implicated in their etiology. Indeed, one leading hypothesis regarding the basis of clinically observed sex differences in psychopathology argues that differences in stress susceptibility and stress exposure play key roles. Consistent with this, differences in stress susceptibility and reactivity in females compared to males have been documented across multiple species. A wide range of environmental, genetic, and epigenetic factors are also thought to impact stress susceptibility, but whether there are sex differences in the effects of specific susceptibility factors remains understudied. Preclinical work suggests that a history of cocaine exposure can increase susceptibility to stress in males, but whether similar effects occur in females following stimulant exposure has not been established. The current work examined the impact of repeated amphetamine administration on subsequent susceptibility to mild sub-chronic stress in male and female mice. In addition to examining behavior, potential sex differences in the effects of stress and amphetamine on the expression of several genes were evaluated. Our results reveal several significant sex differences in the behavioral effects of amphetamine and stress in the elevated plus maze, forced swim test, and novelty-suppressed feeding test. However, in contrast to our initial hypothesis, a history of amphetamine did not lead to an overall increase in stress susceptibility across multiple tests in males or females.

Astrocytic Regulation of Cocaine Locomotor Sensitization in EcoHIV Infected Mice.

Cocaine use disorder (CUD) is highly comorbid with HIV infection and worsens HIV outcomes. Preclinical research on the outcomes of HIV infection may yield crucial information on neurobehavioral changes resulting from chronic drug exposure in people living with HIV (PLWH). Repeated exposure to cocaine alters behavioral responses to cocaine. This includes development of cocaine locomotor sensitization - or increased locomotor responses to the same doses of cocaine - which depends on nucleus accumbens (NAc) neural plasticity. NAc astrocytes are key regulators of neural activity and plasticity, and their function can be impaired by cocaine exposure and HIV infection, thus implicating them as potential regulators of HIV-induced changes in behavioral response to cocaine. To characterize the effects of HIV infection on cocaine locomotor sensitization, we employed the EcoHIV mouse model to assess changes in locomotor responses after repeated cocaine (10mg/kg) exposure and challenge. EcoHIV infection potentiated expression of cocaine sensitization. We also identified EcoHIV-induced increases in expression of the astrocytic nuclear marker Sox9 selectively in the NAc core. To investigate whether modulation of NAc astrocytes could reverse EcoHIV-induced deficits, we employed a chemogenetic approach. We found that chemogenetic activation of NAc astrocyte Gq signaling attenuated EcoHIV-enhanced cocaine sensitization. We propose that HIV infection contributes to cocaine behavioral sensitization and induces adaptations in NAc astrocytes, while promoting NAc astrocytic Gq-signaling can recover EcoHIV-induced behavioral changes. These findings identify potential cellular substrates of disordered cocaine-driven behavior in the context of HIV infection and point toward strategies to reduce cocaine-related behavior in PLWH.

Cannabidiol or ketamine for preventing the impact of adolescent early drug initiation on voluntary ethanol consumption in adulthood.

Few studies have previously evaluated the long-term impact of initiating the combined use of alcohol and cocaine early-in-life during adolescence. Our preclinical study characterized changes in affective-like behavior and/or voluntary ethanol consumption emerging later on in adulthood induced by a prior adolescent drug exposure, as well as tested therapeutical interventions (i.e., cannabidiol or ketamine) to prevent the observed effects. We performed three independent studies with male and female Sprague-Dawley rats, treated in adolescence (postnatal days, PND 29-38) with non-contingent paradigms of ethanol, cocaine, their combination or vehicle. Later on, adult rats were (1) scored for their affective-like state (forced-swim, elevated-plus maze, novelty-suppressed feeding, sucrose preference), (2) allowed to freely drink ethanol for 6weeks (two-bottle choice), or (3) treated with cannabidiol or ketamine before given access to ethanol in adulthood. No signs of increased negative affect were observed in adulthood following the adolescent treatments. However, adolescent ethanol exposure was a risk-factor for later developing an increased voluntary ethanol consumption in adulthood, both for male and female rats. This risk was similar when ethanol was combined with adolescent cocaine exposure, since cocaine alone showed no effects on later ethanol intake. Finally, rats exposed to adolescent ethanol and pretreated in adulthood with cannabidiol (and/or ketamine, but just for females) reduced their ethanol voluntary consumption. Our data provided two therapeutical options capable of preventing the impact of an early drug initiation during adolescence by decreasing voluntary ethanol consumption in adult rats.

Analysis of Sigma-1 Receptor Antagonist BD1047 Effect on Upregulating Proteins in HIV-1-Infected Macrophages Exposed to Cocaine Using Quantitative Proteomics.

HIV-1 infects monocyte-derived macrophages (MDM) that migrate into the brain and secrete virus and neurotoxic molecules, including cathepsin B (CATB), causing cognitive dysfunction. Cocaine potentiates CATB secretion and neurotoxicity in HIV-infected MDM. Pretreatment with BD1047, a sigma-1 receptor antagonist, before cocaine exposure reduces HIV-1, CATB secretion, and neuronal apoptosis. We aimed to elucidate the intracellular pathways modulated by BD1047 in HIV-infected MDM exposed to cocaine. We hypothesized that the Sig1R antagonist BD1047, prior to cocaine, significantly deregulates proteins and pathways involved in HIV-1 replication and CATB secretion that lead to neurotoxicity. MDM culture lysates from HIV-1-infected women treated with BD1047 before cocaine were compared with untreated controls using TMT quantitative proteomics, bioinformatics, Lima statistics, and pathway analyses. Results demonstrate that pretreatment with BD1047 before cocaine dysregulated eighty (80) proteins when compared with the infected cocaine group. We found fifteen (15) proteins related to HIV-1 infection, CATB, and mitochondrial function. Upregulated proteins were related to oxidative phosphorylation (SLC25A-31), mitochondria (ATP5PD), ion transport (VDAC2-3), endoplasmic reticulum transport (PHB, TMED10, CANX), and cytoskeleton remodeling (TUB1A-C, ANXA1). BD1047 treatment protects HIV-1-infected MDM exposed to cocaine by upregulating proteins that reduce mitochondrial damage, ER transport, and exocytosis associated with CATB-induced neurotoxicity.

Sex-specific effects of chronic stress prior to cocaine exposure on cue- vs drug-induced relapse after prolonged abstinence

The comorbidity between cocaine use disorder (CUD) and trauma/stressor-related disorders suggests a connection between neurophysiological changes induced by stress and those that lead to cocaine use. Due to the unexpected and sometimes uncontrollable nature and timing of stressful life events, their capacity to induce drug use poses a significant challenge for the administration of cocaine relapse therapy. This study aims to investigate the impact of chronic stress applied prior to cocaine acquisition on the development of cocaine-seeking behavior after different periods of drug abstinence in male and female rats. Rats were exposed to five days of inescapable footshocks (chronic stress) before undergoing extended access cocaine self-administration. Different groups then underwent forced abstinence periods of 1, 15, or 30 days before cue- and cocaine-induced seeking tests. Results showed that, after 30 days of abstinence, stressed females exhibited higher cue-induced, but not cocaine-induced seeking, compared to female controls and to males. In contrast, at 30 days, stressed males showed higher cocaine-, but not cue-induced seeking, versus controls. Such sex-dependent alterations in motivation and drug effects following prolonged abstinence highlight the importance of considering sex-specific differences in stress-related addiction research. Ongoing work should evaluate other stressors and self-administration models to elucidate neurophysiological and hormonal mechanisms underlying the incubation of cocaine craving. Identifying shared pathways between chronic stress and addiction could offer novel strategies for treating trauma/stress-related substance use disorders in a sex-specific manner.

Mirtazapine decreased cocaine-induced c-fos expression and dopamine release in rats.

Chronic cocaine exposure induces an increase in dopamine release and an increase in the expression of the Fos protein in the rat striatum. It has been suggested that both are necessary for the expression of cocaine-induced alterations in behavior and neural circuitry. Mirtazapine dosing attenuated the cocaine-induced psychomotor and reinforcer effects. The study evaluates the effect of chronic dosing of mirtazapine on cocaine-induced extracellular dopamine levels and Fos protein expression in rats. Male Wistar rats received cocaine (10 mg/Kg; i.p.) during the induction and expression of locomotor sensitization. The mirtazapine (30 mg/Kg; MIR), was administered 30 minutes before cocaine during the cocaine withdrawal. After each treatment, the locomotor activity was recorded for 30 minutes. Animals were sacrificed after treatment administration. Dopamine levels were determined by high-performance liquid chromatographic (HPLC) in the ventral striatum, the prefrontal cortex (PFC), and the ventral tegmental area (VTA) in animals treated with mirtazapine and cocaine. The quantification of c-fos immunoreactive cells was carried out by stereology analysis. Mirtazapine generated a decrease in cocaine-induced locomotor activity. In addition, mirtazapine decreased the amount of cocaine-induced dopamine and the number of cells immunoreactive to the Fos protein in the striatum, PFC, and VTA. These data suggest that mirtazapine could prevent the consolidation of changes in behavior and the cocaine-induced reorganization of neuronal circuits. It would explain the mirtazapine-induced effects on cocaine behavioral sensitization. Thus, these data together could support its possible use for the treatment of patients with cocaine use disorder.

Imaging Dopamine Modulation in Brain Acute Slices for Cocaine Addiction Study with Near-Infrared Carbon Nanotube Sensors

Drug addiction is a pressing issue in modern American society that demands thorough research into its mechanisms. Cocaine locomotor sensitization is a well-established model for understanding the physiological effects of cocaine abuse. Previous studies have established loss of dopamine D2 autoreceptors in striatal tissue as a consequence of locomotor sensitization, yet how these differences in autoreceptor expression affect dopamine signaling remains unclear. Herein, we utilized non-genetically encoded near-infrared fluorescent nanosensors based on carbon nanotubes to image dopamine modulation in live acute coronal brain slices. By leveraging dopamine D2 receptor agonists along with the dopamine nanosensor, we developed a method to identify changes in density of functional D2 autoreceptors and dopamine signaling aberrations that accompany addiction, at the level of individual dopamine synapses. We apply the method to compare changes in D2 autoreceptor activity in the Nucleus Accumbens core in cocaine sensitized and saline (control) mice after prolonged cocaine exposure (5 days). Our preliminarily data indicates the decrease in the number of D2 autoreceptor in cocaine sensitized mice, consistent with the previous studies, and suggests that it leads to higher level of dopamine signaling. Furthermore, we confirm dopamine signaling changes by application of D2 Agonists (quinpirole) are from loss of individual dopamine release sites rather than changes in the quantity of dopamine released, or changes in dopamine reuptake kinetics. Our study provides a route to understand the changes in neuromodulation that underlie the neurobiology of addiction and other dopamine-centric neurological conditions.

Synaptogyrin-3 Prevents Cocaine Addiction and Dopamine Deficits.

Synaptogyrin-3, a functionally obscure synaptic vesicle protein, interacts with vesicular monoamine and dopamine transporters, bringing together dopamine release and reuptake sites. Synaptogyrin-3 was reduced by chronic cocaine exposure in both humans and rats, and synaptogyrin-3 levels inversely correlated with motivation to take cocaine in rats. Synaptogyrin-3 overexpression in dopamine neurons reduced cocaine self-administration, decreased anxiety-like behavior, and enhanced cognitive flexibility. Overexpression also enhanced nucleus accumbens dopamine signaling and prevented cocaine-induced deficits, suggesting a putative therapeutic role for synaptogyrin-3 in cocaine use disorder.

Investigating cocaine- and abstinence-induced effects on astrocyte gene expression in the nucleus accumbens.

In recent years, astrocytes have been increasingly implicated in cellular mechanisms of substance use disorders (SUD). Astrocytes are structurally altered following exposure to drugs of abuse; specifically, astrocytes within the nucleus accumbens (NAc) exhibit significantly decreased surface area, volume, and synaptic colocalization after operant self-administration of cocaine and extinction or protracted abstinence (45 days). However, the mechanisms that elicit these morphological modifications are unknown. The current study aims to elucidate the molecular modifications that lead to observed astrocyte structural changes in rats across cocaine abstinence using astrocyte-specific RiboTag and RNA-seq, as an unbiased, comprehensive approach to identify genes whose transcription or translation change within NAc astrocytes following cocaine self-administration and extended abstinence. Using this method, our data reveal cellular processes including cholesterol biosynthesis that are altered specifically by cocaine self-administration and abstinence, suggesting that astrocyte involvement in these processes is changed in cocaine-abstinent rats. Overall, the results of this study provide insight into astrocyte functional adaptations that occur due to cocaine exposure or during cocaine withdrawal, which may pinpoint further mechanisms that contribute to cocaine-seeking behavior.

Exposure of Zebrafish Embryos to Morphine and Cocaine Induces Changes in the Levels of Dopamine and of Proteins Related to the Reward Pathway

Morphine, a drug of abuse used to treat moderate-to-severe pain, elicits its actions by binding to the opioid receptors. Cocaine is an example of a recreational drug that inhibits dopamine reuptake. The molecular effects of morphine and cocaine have been described in different specific brain regions. However, the systemic outcome of these drugs on the whole organism has not been fully addressed. The aim of this study is to analyse the global effects of morphine (10 μM) and cocaine (15 μM) in the expression of proteins related to the reward pathway. Zebrafish embryos were exposed to these drugs from 5 hpf (hours post-fertilisation) to 6 dpf (days post-fertilisation). Dopamine levels were determined by ELISA, and the expression of Fos proteins, Creb, its activated form p-Creb and tyrosine hydroxylase (Th) were examined by Western blot. Both drugs decreased Th levels at 72 hpf and 6 dpf and modified the expression of Fos family members, pCreb and Creb in a time-dependent manner. Morphine and cocaine exposure differentially modified dopamine levels in 72 hpf and 6 dpf zebrafish embryos. Our results indicate that drugs of abuse modify the expression of several proteins and molecules related to the activation of the reward pathway.

The mGlu5 receptor negative allosteric modulator mavoglurant reduces escalated cocaine self-administration in male and female rats

RationaleCocaine use disorder (CUD) is a brain disorder for which there is no Food and Drug Administration-approved pharmacological treatment. Evidence suggests that glutamate and metabotropic glutamate receptor subtype 5 (mGlu5) play critical roles in synaptic plasticity, neuronal development, and psychiatric disorders.ObjectiveIn the present study, we tested the hypothesis that the mGlu5 receptor is functionally involved in intravenous cocaine self-administration and assessed the effects of sex and cocaine exposure history.MethodsWe used a preclinical model of CUD in rats that were allowed long access (LgA; 6 h/day) or short access (ShA; 1 h/day) to intravenous cocaine (750 µg/kg/infusion [0.1 ml]) self-administration. Rats received acute intraperitoneal or oral administration of the mGlu5 receptor negative allosteric modulator mavoglurant (1, 3, and 10 mg/kg) or vehicle.ResultsBoth intraperitoneal and oral mavoglurant administration dose-dependently reduced intravenous cocaine self-administration in the first hour and in the entire 6 h session in rats in the LgA group, with no effect on locomotion. In the ShA group, mavoglurant decreased locomotion but had no effects on cocaine self-administration. We did not observe significant sex × treatment interactions.ConclusionsThese findings suggest that the mGlu5 receptor is involved in escalated cocaine self-administration. These findings support the development of clinical trials of mavoglurant to evaluate its potential therapeutic benefits for CUD.

A Cocaine-Activated Ensemble Exerts Increased Control Over Behavior While Decreasing in Size

BackgroundSubstance use disorder is characterized by long-lasting changes in reward-related brain regions, such as the nucleus accumbens. Previous work has shown that cocaine exposure induces plasticity in broad, genetically defined cell types in the nucleus accumbens; however, in response to a stimulus, only a small percentage of neurons are transcriptionally active—termed an ensemble. Here, we identify an Arc-expressing neuronal ensemble that has a unique trajectory of recruitment and causally controls drug self-administration after repeated, but not acute, cocaine exposure. MethodsUsing Arc-CreERT2 transgenic mice, we expressed transgenes in Arc+ ensembles activated by cocaine exposure (either acute [1 × 10 mg/kg intraperitoneally] or repeated [10 × 10 mg/kg intraperitoneally]). Using genetic, optical, and physiological recording and manipulation strategies, we assessed the contribution of these ensembles to behaviors associated with substance use disorder. ResultsRepeated cocaine exposure reduced the size of the ensemble while simultaneously increasing its control over behavior. Neurons within the repeated cocaine ensemble were hyperexcitable, and their optogenetic excitation was sufficient for reinforcement. Finally, lesioning the repeated cocaine, but not the acute cocaine, ensemble blunted cocaine self-administration. Thus, repeated cocaine exposure reduced the size of the ensemble while simultaneously increasing its contributions to drug reinforcement. ConclusionsWe showed that repeated, but not acute, cocaine exposure induced a physiologically distinct ensemble characterized by the expression of the immediate early gene Arc, which was uniquely capable of modulating reinforcement behavior.

"Coke in the Dope": The Underrecognized Complications of a Cocaine-Adulterated Fentanyl Supply.

The opioid crisis, particularly the "fourth wave" involving fentanyl and stimulants, has been responsible for an alarming increase in overdose deaths in the United States. Although fentanyl contamination in cocaine has gained significant attention, the converse-cocaine-adulterated fentanyl-has been largely overlooked despite its health implications. The rise in concurrent cocaine and fentanyl overdose deaths could be attributed to various factors, from intentional polysubstance use to unintentional adulterations. Cocaine-related health issues may amplify the problem. Four potential pathways for the increased risk of overdose with cocaine-adulterated opioids include enhanced drug reinforcement, potential overdose risk with switching drug samples, altered metabolism of medications used for opioid use disorder, and increased myocardial demand juxtaposed with opioid-induced respiratory depression. With these risks, the importance of drug testing becomes paramount in the unregulated drug market. As polysubstance use overdoses surge, there is an urgent need to understand how drug supplies are changing in order to effectively identify appropriate harm reduction strategies. Specifically, further research is needed evaluating complications of low-level cocaine exposure with chronic/persistent opioid use. The hazards associated with cocaine-adulterated fentanyl emphasize the significance of understanding not only fentanyl's presence in cocaine but also cocaine's role in the fentanyl supply.