Cocaine Response Research Articles

Acute methylphenidate administration reduces cocaine-cue attentional bias

Mechanistic research on behavioral processes underlying substance use disorder might help identify novel targets for interventions development. Drug-related attentional bias and response inhibition deficits have received a great deal of consideration in substance use research, broadly, and cocaine use research, specifically. Studies investigating pharmacological mechanisms that may ameliorate, or further impair, these behaviors relevant to cocaine use are relatively lacking. This study evaluated the impact of acute administration of methylphenidate, a dopamine-favoring reuptake inhibitor, on both gaze-related cocaine-cue-attentional bias and cocaine-cue related disruptions in response inhibition among individuals with cocaine use disorder. Participants (N = 12; 33% female) completed a within-subject, outpatient, acute dosing study. Two sessions were completed in which methylphenidate (60 mg) or placebo were administered followed by completion of an attentional bias task using eye-tracking technology and neutral-cue and cocaine-cue response inhibition tasks. Subjective and physiological effects were also recorded. Significant cocaine cue attentional bias and response inhibition failures were observed during placebo administration. Acute methylphenidate administration reduced cocaine-cue attentional bias as measured by cocaine-cue gaze fixations (dz = 1.04; Bayes Factor = 12.37). No statistically significant effects of methylphenidate were observed on response inhibition (Bayes Factors = 0.17–1.04). Methylphenidate produced prototypical subjective and physiological effects. Although the small sample should be considered, these findings indicate acute manipulation of dopaminergic activity reduced cue-related attentional allocation related to cocaine use disorder. Future research evaluating alternative dopaminergic agents and applications within a clinical setting are needed to determine the clinical significance of targeting this neurobehavioral mechanism.

Social Isolation in Male Rats During Adolescence Inhibits the Wnt/β-Catenin Pathway in the Prefrontal Cortex and Enhances Anxiety and Cocaine-Induced Plasticity in Adulthood.

In adult animals, it is well established that stress has a proactive effect on psychostimulant responses. However, whether only a short period of stress during adolescence can also affect cocaine responses later in life and what mechanisms are involved are unknown. Here, we showed that 5days of social isolation during rat adolescence had a long-term impact on anxiety-like behaviors, cocaine-induced conditioned place preference, and the expression of sensitization during adulthood. At the molecular level, social isolation decreased the activity of the Wnt/β-catenin pathway in the prefrontal cortex (PFC). Furthermore, after the expression of cocaine sensitization, isolated rats showed an increase in this pathway in the nucleus accumbens. Together, these findings suggest that, adolescent social isolation by altering the Wnt/β-catenin pathway in the developing PFC might increase the cocaine responses during adulthood, introducing this pathway as a novel neuroadaptation in the cortical-accumbens connection that may mediate a stress-induced increase in vulnerability to drugs.

Emergence of negative affect as motivation for drug taking in rats chronically self-administering cocaine.

The role of negative affect as a motivational factor in animal models of drug addiction has been underexplored in the context of cocaine self-administration. The present investigation studied the relationship between magnitude of affective response and quantity of cocaine consumed in order to clarify the affective components that drive drug use in a preclinical model. Rats self-administered (SA) cocaine 6h/day for 14 consecutive days while their ultrasonic vocalizations (USVs) were recorded. Animals displayed an increase in 50-kHz call rates (indicating positive affect) when their drug levels were rapidly rising and an increase in 22-kHz call rates (indicating negative affect) when forced to abstain. The rate of 50-kHz calls predicted drug consumption during the 1st week of SA, but not week two. Contrarily, there was a strongly predictive positive association between rate of 22-kHz calls and amount of drug consumed during the 2nd week of SA. Experimental results indicate that after chronic cocaine self-administration, negative affect emerges when animals are deprived of expected drug during withdrawal. Moreover, the increase in USVs indicating negative affect when deprived of drug was directly related to drug intake, concurrent with a decay in the direct relationship between USVs indicating positive affect and drug intake. The present preclinical support for the widely hypothesized shift from positive to negative affect as a salient motivational factor in human drug abuse adds to growing evidence of the unique value of rat USVs for understanding the role of emotion in drug addiction.

Characterization of genetically complex Collaborative Cross mouse strains that model divergent locomotor activating and reinforcing properties of cocaine.

Few effective treatments exist for cocaine use disorders due to gaps in knowledge aboutits complex etiology. Genetically defined animal models provide a useful tool for advancing our understanding of the biological and genetic underpinnings of addiction-related behavior and evaluating potential treatments. However, many attempts at developing mouse models of behavioral disorders were based on overly simplified single gene perturbations, often leading to inconsistent and misleading results in pre-clinical pharmacology studies. A genetically complex mouse model may better reflect disease-related behaviors. Screening defined, yet genetically complex, intercrosses of the Collaborative Cross (CC) mice revealed two lines, RIX04/17 and RIX41/51, with extreme high and low behavioral responses to cocaine. We characterized these lines as well as their CC parents, CC004/TauUnc and CC041/TauUnc, to evaluate their utility as novel model systems for studying the biological and genetic mechanisms underlying behavioral responses to cocaine. Behavioral responses to acute (initial locomotor sensitivity) and repeated (behavioral sensitization, conditioned place preference, intravenous self-administration) exposures to cocaine were assessed. We also examined the monoaminergic system (striatal tissue content and in vivo fast scan cyclic voltammetry), HPA axis reactivity, and circadian rhythms as potential mechanisms for the divergent phenotypic behaviors observed in the two strains, as these systems have a previously known role in mediating addiction-related behaviors. RIX04/17 and 41/51 show strikingly divergent initial locomotor sensitivity to cocaine with RIX04/17 exhibiting very high and RIX41/51 almost no response. The lines also differ in the emergence of behavioral sensitization with RIX41/51 requiring more exposures to exhibit a sensitized response. Both lines show conditioned place preference for cocaine. We determined that the cocaine sensitivity phenotype in each RIX line was largely driven by the genetic influence of one CC parental strain, CC004/TauUnc and CC041/TauUnc. CC004 demonstrates active operant cocaine self-administration and CC041 is unable to acquire under the same testing conditions, a deficit which is specific to cocaine as both strains show operant response for a natural food reward. Examination of potential mechanisms driving differential responses to cocaine show strain differences in molecular and behavioral circadian rhythms. Additionally, while there is no difference in striatal dopamine tissue content or dynamics, there are selective differences in striatal norepinephrine and serotonergic tissue content. These CC strains offer a complex polygenic model system to study underlying mechanisms of cocaine response. We propose that CC041/TauUnc and CC004/TauUnc will be useful for studying genetic and biological mechanisms underlying resistance or vulnerability to the stimulatory and reinforcing effects of cocaine.

Age- and Sex-Specific Plasticity in Dopamine Transporter Function Revealed by Food Restriction and Exercise in a Rat Activity-Based Anorexia Paradigm.

Eating disorders such as anorexia typically emerge during adolescence, are characterized by engagement in compulsive and detrimental behaviors, and are often comorbid with neuropsychiatric disorders and drug abuse. No effective treatments exist. Moreover, anorexia lacks adolescent animal models, contributing to a poor understanding of underlying age-specific neurophysiological disruptions. To evaluate the contribution of dopaminergic signaling to the emergence of anorexia-related behaviors during the vulnerable adolescent period, we applied an established adult activity-based anorexia (ABA) paradigm (food restriction plus unlimited exercise access for 4 to 5 days) to adult and adolescent rats of both sexes. At the end of the paradigm, measures of plasma volume, blood hormone levels, dopamine transporter (DAT) expression and function, acute cocaine-induced locomotion, and brain water weight were taken. Adolescents were dramatically more affected by the ABA paradigm than adults in all measures. In vivo chronoamperometry and cocaine locomotor responses revealed sex-specific changes in adolescent DAT function after ABA that were independent of DAT expression differences. Hematocrit, insulin, ghrelin, and corticosterone levels did not resemble shifts typically observed in patients with anorexia, though decreases in leptin levels aligned with human reports. These findings are the first to suggest that food restriction in conjunction with excessive exercise sex-dependently and age-specifically modulate DAT functional plasticity during adolescence. The adolescent vulnerability to this relatively short manipulation, combined with blood measures, evidence need for an optimized age-appropriate ABA paradigm with greater face and predictive validity for the study of the pathophysiology and treatment of anorexia.SIGNIFICANCE STATEMENTAdolescent rats exhibit a distinctive, sex-specific plasticity in dopamine transporter function and cocaine response after food restriction and exercise access; this plasticity is both absent in adults and not attributable to changes in dopamine transporter expression levels. These novel findings may help explain sex differences in vulnerability to eating disorders and drug abuse during adolescence.

Epigenetic Regulation of Hippocampal Fosb Expression Controls Behavioral Responses to Cocaine.

Drug addiction results in part from maladaptive learning, including the formation of strong associations between the drug and the circumstances of consumption. However, drug-induced changes in gene expression underlying the saliency of these associations remain understudied. Consolidation of explicit memories occurs within the hippocampus, and we have shown that spatial learning induces expression of the transcription factor ΔFosB in hippocampus and that this induction is critical for learning. Drugs of abuse also upregulate ΔFosB in hippocampus, but the mechanism of its induction by cocaine and its role in hippocampus-dependent cocaine responses is unknown. We investigated differences in mouse dorsal and ventral hippocampal ΔFosB expression in response to chronic cocaine, because these regions appear to regulate distinct cocaine-related behaviors. We found that cocaine-mediated induction of ΔFosB was subregion-specific, and that ΔFosB transcriptional activity in both the dorsal and ventral hippocampus is necessary for cocaine conditioned place preference. Further, we characterize changes in histone modifications at the FosB promoter in hippocampus in response to chronic cocaine and found that locus-specific epigenetic modification is essential for FosB induction and multiple hippocampus-dependent behaviors, including cocaine place preference. Collectively, these findings suggest that exposure to cocaine induces histone modification at the hippocampal FosB gene promoter to cause ΔFosB induction critical for cocaine-related learning.SIGNIFICANCE STATEMENT Although cocaine addiction is driven in part by the formation of indelible associations between the drug and the environment, paraphernalia, and circumstances of use, and although this type of associative learning is dependent upon changes in gene expression in a brain region called the hippocampus, the mechanisms by which cocaine alters hippocampal gene expression to drive formation of these associations is poorly understood. Here, we demonstrate that chronic cocaine engages locus-specific changes in the epigenetic profile of the FosB gene in the hippocampus, and that these alterations are required for cocaine-dependent gene expression and cocaine-environment associations. This work provides novel insight into addiction etiology and potential inroads for therapeutic intervention in cocaine addiction.

Conditional, inducible gene silencing in dopamine neurons reveals a sex-specific role for Rit2 GTPase in acute cocaine response and striatal function.

Dopamine (DA) signaling is critical for movement, motivation, and addictive behavior. The neuronal GTPase, Rit2, is enriched in DA neurons (DANs), binds directly to the DA transporter (DAT), and is implicated in several DA-related neuropsychiatric disorders. However, it remains unknown whether Rit2 plays a role in either DAergic signaling and/or DA-dependent behaviors. Here we leveraged the TET-OFF system to conditionally silence Rit2 in Pitx3IRES2-tTA mouse DANs. Following DAergic Rit2 knockdown (Rit2-KD), mice displayed an anxiolytic phenotype, with no change in baseline locomotion. Further, males exhibited increased acute cocaine sensitivity, whereas DAergic Rit2-KD suppressed acute cocaine sensitivity in females. DAergic Rit2-KD did not affect presynaptic TH and DAT protein levels in females, nor was TH was affected in males; however, DAT was significantly diminished in males. Paradoxically, despite decreased DAT levels in males, striatal DA uptake was enhanced, but was not due to enhanced DAT surface expression in either dorsal or ventral striatum. Finally, patch recordings in nucleus accumbens (NAcc) medium spiny neurons (MSNs) revealed reciprocal changes in spontaneous EPSP (sEPSP) frequency in male and female D1+ and D2+ MSNs following DAergic Rit2-KD. In males, sEPSP frequency was decreased in D1+, but not D2+, MSNs, whereas in females sEPSP frequency decreased in D2+, but not D1+, MSNs. Moreover, DAergic Rit2-KD abolished the ability of cocaine to reduce sEPSP frequency in D1+, but not D2+, male MSNs. Taken together, our studies are among the first to acheive AAV-mediated, conditional and inducible DAergic knockdown in vivo. Importantly, our results provide the first evidence that DAergic Rit2 expression differentially impacts striatal function and DA-dependent behaviors in males and females.

Strain differences in maternal neuroendocrine and behavioral responses to stress and the relation to offspring cocaine responsiveness

Early life stress exposure, including prenatal stress (PNS), influences subsequent risk for many disorders, including substance abuse, and these effects interact with genetic factors to determine risk for disease. We previously demonstrated gene X environmental interactions across the BXD recombinant inbred mouse strain panel and their progenitor strains in PNS modulation of cocaine-induced reward and locomotion. Critical to dissecting genetic interactions with PNS is consideration of the modes of stress transmission to the offspring. Both maternal neuroendocrine responses during stress and subsequent maternal-offspring interactions following stress may serve as transmission modes for PNS-induced changes in cocaine responsiveness. Therefore, we characterized the maternal stress response by measuring restraint stress-induced plasma corticosterone (CORT) during gestation as well as effects of restraint stress on dam-pup contact in the first 10 postnatal days in BXD and progenitor mouse strains. Restraint stress interacted with strain to affect plasma CORT levels and dam-pup contact, indicating heritable variation of the maternal stress response. Furthermore, strain-level variance in maternal stress response correlated to the impact on cocaine response exhibited by adult offspring. These findings implicate multiple modes of maternal stress response in alterations of offspring drug responsiveness and indicate that assessment of maternal endocrine and behavioral responses during early life can be utilized to dissect the complex intersection of maternal factors, the response of the offspring and genetics.

Discovery of early life stress interacting and sex-specific quantitative trait loci impacting cocaine responsiveness.

Addiction vulnerability involves complex gene X environment interactions leading to a pathological response to drugs. Identification of the genes involved in these interactions is an important step in understanding the underlying neurobiology and rarely have such analyses examined sex-specific influences. To dissect this interaction, we examined the impact of prenatal stress (PNS) on cocaine responsiveness in male and female mice of the BXD recombinant inbred panel. BXD strains were subjected to timed mating and assigned to PNS or control groups. PNS dams were subjected to restraint stress (1-hr restraint, three times daily) starting between embryonic day (E) 11 and 14 and continued until parturition. Adult male and female, control and PNS offspring were tested for locomotor response to initial and repeated cocaine injections (sensitization) as well as cocaine-induced conditioned place preference (CPP). Strain, PNS, and sex interacted to modulate initial and sensitized cocaine-induced locomotion, as well as CPP. Moreover, a quantitative trait locus (QTL) interacting with PNS regulating initial locomotor response to cocaine (chromosome X, 37.91 to 50.95Mb) was identified. Also PNS-independent, female-specific QTLs regulating CPP (chromosome 11, 65.50 to 81.31Mb) and sensitized cocaine-induced locomotion (chromosome 16, 95.79 to 98.32Mb) were identified. Publicly available mRNA expression data were utilized to identify cis-eQTL and transcript covariation with the behavioural phenotype to prioritize candidate genes; including Aifm1. These QTL encompass genes that may moderate genetic susceptibility to PNS and interact with sex to determine adult responsiveness to cocaine and addiction vulnerability. This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Postsynaptic Mechanisms Render Syn I/II/III Mice Highly Responsive to Psychostimulants.

BackgroundSynapsins are encoded by SYN I, SYN II, and SYN III, and they regulate neurotransmitter release by maintaining a reserve pool of synaptic vesicles.MethodsPresynaptic dopamine responses to cocaine were examined by microdialysis, and postsynaptic responses were evaluated to various dopamine receptor agonists in the open field with SynI/SynII/SynIII triple knockout mice.ResultsTriple knockout mice showed enhanced spontaneous locomotion in a novel environment and were hyper-responsive to indirect and direct D1 and D2 dopamine agonists. Triple knockout animals appeared sensitized to cocaine upon first open field exposure; sensitization developed across days in wild-type controls. When mutants were preexposed to a novel environment before injection, cocaine-stimulated locomotion was reduced and behavioral sensitization retarded. Baseline dopamine turnover was enhanced in mutants and novel open field exposure increased their striatal dopamine synthesis rates. As KCl-depolarization stimulated comparable dopamine release in both genotypes, their readily releasable pools appeared indistinguishable. Similarly, cocaine-induced hyperlocomotion was indifferent to blockade of newly synthesized dopamine and depletion of releasable dopamine pools. Extracellular dopamine release was similar in wild-type and triple knockout mice preexposed to the open field and given cocaine or placed immediately into the arena following injection. Since motor effects to novelty and psychostimulants depend upon frontocortical-striatal inputs, we inhibited triple knockout medial frontal cortex with GABA agonists. Locomotion was transiently increased in cocaine-injected mutants, while their supersensitive cocaine response to novelty was lost.ConclusionsThese results reveal presynaptic dopamine release is not indicative of agonist-induced triple knockout hyperlocomotion. Instead, their novelty response occurs primarily through postsynaptic mechanisms and network effects.

Selective D2 and D3 receptor antagonists oppositely modulate cocaine responses in mice via distinct postsynaptic mechanisms in nucleus accumbens.

The dopamine D3 receptor (D3R) has emerged as a promising pharmacotherapeutic target for the treatment of several diseases including schizophrenia, Parkinson's disease, and substance use disorders. However, studies investigating the D3R's precise role in dopamine neurotransmission or how it may be exploited to modulate responses to drugs of abuse have produced contrasting results, in part because most D3R-targeted compounds often also interact with D2 receptors (D2R). To resolve this issue, we set out to systematically characterize and compare the consequences of selective D2R or D3R antagonists on the behavioral-stimulant properties of cocaine in mice, and to identify putative neurobiological mechanisms underlying their behavior-modifying effects. Pretreatment with the selective D2R antagonist L-741,626 attenuated, while pretreatment with the selective D3R antagonist PG01037 enhanced, the locomotor-activating effects of both acute cocaine administration as well as sensitization following repeated cocaine dosing. While both antagonists potentiated cocaine-induced increases in presynaptic dopamine release, we report for the first time that D3R blockade uniquely facilitated dopamine-mediated excitation of D1-expressing medium spiny neurons in the nucleus accumbens. Collectively, our results demonstrate that selective D3R antagonism potentiates the behavioral-stimulant effects of cocaine in mice, an effect that is in direct opposition to that produced by selective D2R antagonism or nonselective D2-like receptor antagonists, and is likely mediated by facilitating D1-mediated excitation in the nucleus accumbens. These findings provide novel insights into the neuropharmacological actions of D3R antagonists on mesolimbic dopamine neurotransmission and their potential utility as pharmacotherapeutics.

Wheel-running exercise before and during gestation against acute and sensitized cocaine psychomotor-activation in offspring

While animal research has consistently reported preventive effects of exercise against drug abuse vulnerability, little is known about the influence of the developmental stage during which exercise is displayed on addictive drugs responsiveness. This study aimed to determine whether prenatal exercise could attenuate acute cocaine reactivity and psychomotor sensitization in youth offspring. We used a split-plot factorial design where C57BL/6 J females were randomly assigned into sedentary or exercised (wheel-running) conditions before and during gestation, the wheels being removed on gestational day 18. Offspring were weaned, gendered and individually housed on 24–28 days old. At 38–42 days old, they were tested for their acute psychomotor responsiveness to 8 mg/kg cocaine and their initiation of sensitization over 8 additional once-daily administrations, the long-term expression of sensitization occurring 30 days later. Adolescent females born from exercised mothers were much less responsive to the acute psychomotor-stimulating effect of cocaine than those born from sedentary mothers (d = 0.75, p = 0.02), whereas there was no evidence for such a difference in males (d = 0.34, p = 0.17). However, we did not find sizeable attenuating effects of prenatal exercise on the initiation and the long-term expression of the psychomotor-activating effect of cocaine, in either sex (Cohen’s ds varying from −0.13 to 0.39). These results suggest that prenatal exercise may induce initial protection against cocaine responsiveness in youth females, a finding that warrants further research.

Oral Methylphenidate Treatment of an Adolescent ADHD Rat Model Does Not Alter Cocaine-Conditioned Place Preference during Adulthood: A Negative Report.

The stimulant, methylphenidate (MPH), is commonly used to treat attention deficit hyperactivity disorder (ADHD) and has been increasingly prescribed for school age children and adolescents. Concerns regarding its long-term effects on later substance use disorders (SUDs) have been raised. Previous animal studies have produced contradictory results regarding whether early exposure to MPH increases or protects against SUD in adulthood. The goal of our study was to determine if clinically relevant doses of MPH during adolescence alter cocaine responsiveness in adulthood in a rat model of ADHD, the spontaneous hypertensive rat (SHR). We pretreated SHRs with saline or MPH (2.5 mg/kg once or twice day) via oral gavage during their dark cycle from postnatal day 35 (p35) to p44. Adult rats (p80) were assessed in an eight-session cocaine-conditioned place preference test (CPP). Four doses of cocaine were administered via intraperitoneal injection (i.p.) during the conditioning sessions: 1, 5, 10 and 20 mg/kg. Once per day MPH treatment had a small sensitizing effect on baseline general locomotor activity in a novel environment at p80 as well as a limited suppressive effect on reward-specific locomotor activity as measured by the decreased preference to enter the cocaine-paired chamber. This treatment did not have any effect on the amount of time that rats chose to spend in the cocaine-paired chamber. Twice per day MPH treatment had no effect on locomotion or drug-preference. Our results suggest that MPH treatment of ADHD rats during adolescence does not alter preference for cocaine in adulthood.

A novel role for E2F3b in regulating cocaine action in the prefrontal cortex.

Drug abuse is a multifaceted disorder that involves maladaptive decision making. Long-lasting changes in the addicted brain are mediated by a complex circuit of brain reward regions. The prefrontal cortex (PFC) is one region in which chronic drug exposure changes expression and function of upstream transcriptional regulators to alter drug responses and aspects of the addicted phenotype. We reported recently that the transcription factor E2F3a is a critical mediator of cocaine responses in the nucleus accumbens. E2F3a is one of two splice variants of the E2f3 gene; the other is E2F3b. Another recent study predicted E2F3 as an upstream regulator of the transcriptional response to cocaine self-administration (SA)in PFC. Based on previous findings that E2F3a and E2F3b have divergent regulatory roles, we set out to study the putative transcriptional role of these transcripts in PFC in the context of repeated I.P. cocaine exposure. We implemented viral-mediated isoform-specific gene manipulation, RNA-sequencing, advanced bioinformatics analyses, and animal behavior to determine how E2F3a and E2F3b contribute to persistent cocaine-induced transcriptional changes in PFC. We show that E2F3b, but not E2F3a, in PFC is critical for cocaine locomotor and place preference behaviors. Interestingly, RNA-seq of PFC following E2f3b overexpression or I.P. cocaine exposure showed very different effects on expression levels of differentially expressed genes. However, we found that E2F3b drives a similar transcriptomic pattern to that of cocaine SA with overlapping upstream regulators and downstream pathways predicted. These findings reveal a novel transcriptional mechanism in PFC that controls behavioral and molecular responses to cocaine.

Glutamate-Glutamine Transfer and Chronic Stress-Induced Sex Differences in Cocaine Responses

Substance use disorders (SUD) often co-occur with other mental disorders such as major depression (MD). Our previous findings revealed sex-dependent changes in extracellular levels of glutamate (Glu) and glutamine (Gln) in the nucleus accumbens (NAc) in Long–Evans rats that were exposed to 21 days of chronic social defeat stress (CSDS), which models MD. The current study investigated the role of a Gln transporter called sodium-coupled neutral amino acid transporter subtype 1/2 (SNAT 1/2), phosphate-activated glutaminase (PAG), and astrocytic glutamate transporter-1 (GLT-1) on CSDS animals exposed to cocaine. Before cocaine exposure, CSDS males already showed decreased levels of SNAT 1/2 in the NAc and prefrontal cortex (PFC) compared to non-CSDS controls. The reduction in SNAT 1/2 levels was associated with an increase in Gln localization in the mitochondrial outer membrane in accumbal glutamatergic nerve terminals projecting from the PFC. CSDS females showed increased GLT-1 levels in the NAc and PFC compared to non-CSDS controls. Both acute and repeated cocaine exposure attenuated locomotor responses in CSDS males but increased those in CSDS females. Cocaine reduced SNAT 1/2 levels in the NAc but increased them in the PFC in CSDS males. Additionally, both PAG and GLT-1 levels were increased in the PFC in CSDS males. On the other hand, cocaine reduced SNAT 1/2 and GLT-1 levels in the NAc and PFC in CSDS females. Our results show that CSDS altered locomotor responses upon cocaine exposure in a sex-dependent manner that may be mediated by molecules associated with the Glu-Gln transfer.

Dopaminergic Perturbations from Food Restriction and Exercise are Sex‐Dependently Amplified During Adolescence

Eating disorders, which are 2.5‐fold more prevalent in females than males, typically emerge during adolescence. Afflicting at least 3 percent of teenagers, eating disorders such as anorexia nervosa, bulimia nervosa, and binge eating disorder entail severe health consequences in addition to their psychological toll. Yet no effective treatments for eating disorders exist. An established regulator of both eating behaviors and physical activity, the dopaminergic system undergoes a sensitive maturation period during adolescence. However, studies into the role of the dopaminergic system in ontogeny of eating disorders are lacking, as are investigations into dopaminergic system maturation in adolescent females. Here we measured function of the dopamine transporter (DAT), a critical regulator of dopaminergic signaling, using both in vivo high‐speed chronoamperometry and locomotor assays of acute cocaine response. Employing an activity‐based anorexia paradigm for 4–5 days, we investigated how food restriction, free exercise on a running wheel, or the combination thereof impacted DAT function in adult (postnatal day 90) and adolescent (postnatal day 30) Sprague‐Dawley rats of both sexes. Food restriction alone or with exercise in adolescent rats of both sexes produced leftward shifts in the dose‐response to the locomotor‐promoting effects of cocaine, though the maximal response to cocaine was blunted in females within these two groups. In adults, only food restricted females exhibited a significant increase in maximal cocaine‐induced locomotor response. Clearance of dopamine in dorsal striatum was not significantly altered by food restriction and/or exercise in adults. In contrast, food restriction plus exercise significantly attenuated dopamine clearance in adolescent males, and food restriction alone or combined with exercise elicited pronounced dopamine clearance reductions in adolescent females. Together, these findings suggest that adolescent plasticity of the dopaminergic system confers – particularly in females – vulnerability to eating disorders and persistence of associated unhealthy behaviors (e.g., compulsive exercise). Therefore, drugs that enhance dopamine uptake or otherwise reduce dopamine signaling duration may prove efficacious in the treatment of emerging adolescent eating disorders. Ongoing experiments are evaluating striatal DAT expression in these animals, and future experiments will focus on optimizing longer term food restriction and exercise conditions in adolescents to facilitate investigation of pharmacologic interventions.Support or Funding InformationThis research was supported by R21 DA038504 to LCD. TLG is supported by T32 DA031115 to Charles P. France.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Highly sensitive and specific on-site detection of serum cocaine by a low cost aptasensor

Cocaine is one of the most used illegal recreational drugs. Developing an on-site test for cocaine use detection has been a focus of research effort, since it is essential to the control and legal action against drug abuse. Currently most of cocaine detection methods are time-consuming and require special or expensive equipment, and the detection often suffers from high cross-reactivity with cocaine metabolites and relative low sensitivity with the best limit of detection reported at sub nanomolar (nM) level. In this work, an aptasensor has been developed using capacitive monitoring of sensor surface incorporating alternating current electrokinetics effects to speed up molecular transport and minimize matrix effects. The aptasensor is rapid, low cost, highly sensitive and specific as well as simple-to-use for the detection of cocaine from serum. The assay has a sample-to-result time of 30 s, a limit of detection of 7.8 fM, and a linear response for cocaine ranging from 14.5fM to 14.5pM in standard buffer, which are great improvements from other reported cocaine sensors. Special buffer is used for serum cocaine detection, and a limit of detection of 13.4 fM is experimentally demonstrated for cocaine spiked in human serum (equivalent to 1.34pM cocaine in neat serum). The specificity of the biosensor is also demonstrated with structurally similar chemicals, ecgonine ethyl ester and methylecgonidine. This biosensor shows high promise in detection of low levels of cocaine from complex matrices.

Dose response of acute cocaine on sleep/waking behavior in mice

Chronic cocaine use has been associated with sleep disturbances, both during active use periods and during withdrawal and abstinence. Acute cocaine also increases waking at the expense of slow wave sleep and Rapid Eye Movement in non-human subjects. However, the effects of acute cocaine on sleep/waking activity in mice, a rodent model commonly used in both sleep and addiction research due to its high genetic tractability, has yet to be investigated. Sleep/waking activity was measured via polysomnography following IP administration of three doses of cocaine (3.6, 9.6, 18 mg/kg) and vehicle control in male C57BL/6 mice. Cocaine dose-dependently increased sleep latency, increased waking time and increased fast EEG activity within waking. Increases in waking occurred primarily during the first hour following injection, followed by rebound SWS sleep. Sleep/waking activity normalized within a 24-hour period. As with humans and other rodents, cocaine dose dependently reduces sleep in a wildtype strain of mice commonly used in reward and addiction research.

Estrogen Receptor β in the Nucleus Accumbens Regulates the Rewarding Properties of Cocaine in Female Mice.

BackgroundFemales are more vulnerable to developing cocaine addiction compared with males, a phenomenon that may be regulated by the steroid hormone 17β-estradiol. 17β-Estradiol enhances cocaine reward as measured by the conditioned place preference test. It is currently not known which estrogen receptor is involved or the neuroanatomical locations in which estrogen receptors act to enhance cocaine responses. The purpose of this study was to determine if the estrogen receptors ERα and ERβ regulate cocaine conditioned place preference in mice and whether they act in the nucleus accumbens, a brain region critically involved in the development of cocaine abuse.MethodsOvariectomized mice were treated with 17β-estradiol or agonists selective for ERα or ERβ and tested for cocaine conditioned place preference and for c-fos expression in the nucleus accumbens. Female mice with intact ovaries were also tested for cocaine conditioned place preference after RNA interference-mediated knockdown of ERα or ERβ in the nucleus accumbens.ResultsWe found that mice treated with 17β-estradiol or an ERβ agonist exhibited increased cocaine conditioned place preference, while knockdown of ERβ, but not ERα, in the nucleus accumbens of females with intact ovaries abrogated cocaine conditioned place preference. Acute treatment with 17β-estradiol or an ERβ agonist induced expression of the immediate-early gene c-fos in the nucleus accumbens, whereas the ERα agonist did not.ConclusionsThese data indicate that ERβ in the nucleus accumbens regulates the development of cocaine conditioned place preference in female mice. 17β-Estradiol may activate neurons in the nucleus accumbens via ERβ. We speculate that this might increase the saliency of cocaine cues that predict drug reward.

Influence of preoptic estradiol on behavioral and neural response to cocaine in female Sprague-Dawley rats.

Systemic estradiol (E2) increases the behavioral and neural response to cocaine. Where inthe brain E2 acts to modulate cocaine response is not entirely clear. Evidence supports a role in this modulation for several candidate regions, including the medial preoptic area (mPOA). This study examined whether manipulation of E2 in the mPOA modulates differing behavioral responses to cocaine and whether this is reflected in differing levels of c-Fos in the NAc following cocaine administration. Female rats received ovariectomies and bilateral cannulations of the mPOA. They then received either artificial cerebrospinal fluid (aCSF) or E2 microinjections into the mPOA the day before receiving systemic injections of saline or cocaine (5 or10mg/kg). Conditioned-place preference (CPP) to cocaine and locomotor activation were then obtained. Animals receiving 10 mg/kg, but not 5 mg/kg, cocaine developed significant CPP, and those receiving E2 into the mPOA expressed greater CPP than those receiving microinjections of only aCSF at both doses (p < 0.05, d > 0.80). Cocaine also caused significant psychomotor activation, but this was not dependent on microinjection of E2 in the mPOA. Finally, animals that received cocaine had increased NAc core and shell c-Fos relative to animals that received saline, with animals receiving both E2 microinjections and systemic cocaine expressing the highest activation in the caudal NAc, compared to rats receiving aCSF microinjections and systemic cocaine (p = 0.05, d = 0.70). These results indicate that E2 in the mPOA facilitates the behavioral response and neural activation that follows cocaine administration. Furthermore, they confirm the close relationship between the mPOA and cocaine response.