Repeated dosing with oral cocaine in humans: assessment of direct effects, withdrawal, and pharmacokinetics

Enhancing translation: A need to leverage complex preclinical models of addictive drugs to accelerate substance use treatment options

Preclinical models of addictive drugs have been developed for decades to model aspects of the clinical experience in substance use disorders (SUDs). These include passive exposure as well as volitional intake models across addictive drugs and have been utilized to also measure withdrawal symptomatology and potential neurobehavioral mechanisms underlying relapse to drug seeking or taking. There are a number of Food and Drug Administration (FDA)-approved medications for SUDs, however, many demonstrate low clinical efficacy as well as potential sex differences, and we also note gaps in the continuum of care for certain aspects of clinical experiences in individuals who use drugs. In this review, we provide a comprehensive update on both frequently utilized and novel behavioral models of addiction with a focus on translational value to the clinical experience and highlight the need for preclinical research to follow epidemiological trends in drug use patterns to stay abreast of clinical treatment needs. We then note areas in which models could be improved to enhance the medications development pipeline through efforts to enhance translation of preclinical models. Next, we describe neuroscience efforts that can be leveraged to identify novel biological mechanisms to enhance medications development efforts for SUDs, focusing specifically on advances in brain transcriptomics approaches that can provide comprehensive screening and identification of novel targets. Together, the confluence of this review demonstrates the need for careful selection of behavioral models and methodological parameters that better approximate the clinical experience combined with cutting edge neuroscience techniques to advance the medications development pipeline for SUDs.

A two-year review of cocaine findings in impaired driving investigations in Ontario, Canada

Drug-impaired driving is an increasing public safety concern across Canada, particularly due to the demonstrated increase in use of recreational drugs such as cocaine. Cocaine is a central nervous system stimulant drug; however, it can impair an individual's driving ability in both the stimulant and crash phases. Despite the scientific consensus regarding cocaine's potential for driving impairment, there is relatively little information available regarding blood concentrations and associated observations of impairment in suspected impaired drivers. Retrospective data analysis was performed to evaluate suspected impaired driving cases in which cocaine and/or benzoylecgonine were detected alone, or in combination with other drugs, in blood and urine samples submitted to the Toxicology Section of the Centre of Forensic Sciences with incident dates between 2021 and 2022. Cocaine and/or benzoylecgonine were detected in 46% (blood) and 66% (urine) of the total impaired driving samples submitted. In 41 cases where cocaine and/or benzoylecgonine were the only drug finding in blood, concentrations of cocaine and benzoylecgonine ranged from 0.0073 to 0.26 mg/L (mean 0.096 mg/L) and 0.13 to 5.3 mg/L (mean 2.1 mg/L), respectively. Driving observations reported by the arresting officer in cases where cocaine and/or benzoylecgonine were the only drug finding in blood and urine included the driver being involved in a collision, the vehicle leaving the roadway, erratic driving and the driver being asleep at the wheel; observations of drug impairment reported by the drug recognition expert at the time of driver evaluation included abnormal speech patterns, poor balance/incoordination, abnormal body movements and the individual falling asleep. The results provide concentrations of cocaine and benzoylecgonine observed in suspected impaired drivers, insight into observations that may be associated with prior cocaine use and additional information to inform on the effects of cocaine on driving.

Effects of self- and experimenter-administered cocaine on subsequent ethanol drinking in rhesus monkeys

BACKGROUND

One possible reason for the lack of FDA-approved pharmacotherapies to treat cocaine use disorder (CUD) is that, although cocaine is typically used in combination with alcohol, it is studied in isolation in preclinical studies. A better understanding of the cocaine-alcohol interactions that promote polysubstance use (PSU) will improve animal models of CUD and hasten pharmacotherapy development. We used a rhesus monkey model of cocaine-alcohol PSU to investigate one possible mechanism: that alcohol is used to mitigate negative effects associated with termination of cocaine use.

METHODS

In 6 adult male rhesus monkeys, the relationship between self-administered cocaine intake and oral ethanol intake 2hours later was examined during self-administration of cocaine (0.0003-0.3mg/kg per injection, i.v.) under a fixed-ratio 30 schedule (FR30) or a progressive-ratio (PR) schedule. Next, ethanol consumption was measured 0-120minutes after experimenter-administered cocaine (0.3-1.7mg/kg, i.v.).

RESULTS

Self-administered cocaine intake under both FR30 and PR schedules was unrelated to oral ethanol intakes 2hours later. When cocaine was administered non-contingently, cocaine decreased ethanol intake as well as intake of a non-alcoholic solution in monkeys who never consumed ethanol (n=4) in a time- and dose-dependent manner.

CONCLUSIONS

Taken together, the results do not provide evidence for cocaine-induced increases in ethanol consumption. By extension, the results do not support the hypothesis that cocaine users drink alcohol to counteract negative effects that occur after terminating use. This finding implies either that such effects do not exist or that such effects exist but are unaffected by ethanol.

Deep brain stimulation of the nucleus accumbens shell attenuates cocaine withdrawal but increases cocaine self-administration, cocaine-induced locomotor activity, and GluR1/GluA1 in the central nucleus of the amygdala in male cocaine-dependent rats

BACKGROUND

Cocaine addiction is a major public health problem. Despite decades of intense research, no effective treatments are available. Both preclinical and clinical studies strongly suggest that deep brain stimulation of the nucleus accumbens (NAcc) is a viable target for the treatment of cocaine use disorder (CUD).

OBJECTIVE

Although previous studies have shown that DBS of the NAcc decreases cocaine seeking and reinstatement, the effects of DBS on cocaine intake in cocaine-dependent animals have not yet been investigated.

METHODS

Rats were made cocaine dependent by allowing them to self-administer cocaine in extended access conditions (6 h/day, 0.5 mg/kg/infusion). The effects of monophasic bilateral high-frequency DBS (60 μs pulse width and 130 Hz frequency) stimulation with a constant current of 150 μA of the NAcc shell on cocaine intake was then evaluated. Furthermore, cocaine-induced locomotor activity, irritability-like behavior during cocaine abstinence, and the levels of the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits 1 and 2 (GluR1/GluA1 and GluR2/GluA2) after DBS were investigated.

RESULTS

Contrary to our expectations, DBS of the NAcc shell induced a slight increase in cocaine self-administration, and increased cocaine-induced locomotion after extended access of cocaine self-administration. In addition, DBS decreased irritability-like behavior 18 h into cocaine withdrawal. Finally, DBS increased both cytosolic and synaptosomal levels of GluR1, but not GluR2, in the central nucleus of the amygdala but not in other brain regions.

CONCLUSIONS

These preclinical results with cocaine-dependent animals support the use of high-frequency DBS of the NAcc shell as a therapeutic approach for the treatment of the negative emotional state that emerges during cocaine abstinence, but also demonstrate that DBS does not decrease cocaine intake in active, long-term cocaine users. These data, together with the existing evidence that DBS of the NAcc shell reduces the reinstatement of cocaine seeking in abstinent animals, suggest that NAcc shell DBS may be beneficial for the treatment of the negative emotional states and craving during abstinence, although it may worsen cocaine use if individuals continue drug use.

Interaction between cocaine use and sleep behavior: A comprehensive review of cocaine's disrupting influence on sleep behavior and sleep disruptions influence on reward seeking

Dopamine, orexin (hypocretin), and adenosine systems have dual roles in reward and sleep/arousal suggesting possible mechanisms whereby drugs of abuse may influence both reward and sleep/arousal. While considerable variability exists across studies, drugs of abuse such as cocaine induce an acute sleep loss followed by an immediate recovery pattern that is consistent with a normal response to loss of sleep. Under more chronic cocaine exposure conditions, an abnormal recovery pattern is expressed that includes a retention of sleep disturbance under withdrawal and into abstinence conditions. Conversely, experimentally induced sleep disturbance can increase cocaine seeking. Thus, complementary, sleep-related therapeutic approaches may deserve further consideration along with development of non-human models to better characterize sleep disturbance-reward seeking interactions across drug experience.

Single Exposure to Cocaine Impairs Reinforcement Learning by Potentiating the Activity of Neurons in the Direct Striatal Pathway in Mice

Plasticity in the glutamatergic synapses on striatal medium spiny neurons (MSNs) is not only essential for behavioral adaptation but also extremely vulnerable to drugs of abuse. Modulation on these synapses by even a single exposure to an addictive drug may interfere with the plasticity required by behavioral learning and thus produce impairment. In the present work, we found that the negative reinforcement learning, escaping mild foot-shocks by correct nose-poking, was impaired by a single in vivo exposure to 20 mg/kg cocaine 24 h before the learning in mice. Either a single exposure to cocaine or reinforcement learning potentiates the glutamatergic synapses on MSNs expressing the striatal dopamine 1 (D1) receptor (D1-MSNs). However, 24 h after the cocaine exposure, the potentiation required for reinforcement learning was disrupted. Specific manipulation of the activity of striatal D1-MSNs in D1-cre mice demonstrated that activation of these MSNs impaired reinforcement learning in normal D1-cre mice, but inhibition of these neurons reversed the reinforcement learning impairment induced by cocaine. The results suggest that cocaine potentiates the activity of direct pathway neurons in the dorsomedial striatum and this potentiation might disrupt the potentiation produced during and required for reinforcement learning.

Novel mucosal adjuvant, mastoparan-7, improves cocaine vaccine efficacy

Cocaine is one of the most potent and addictive psychostimulants known and there are no available pharmacotherapies to treat cocaine addiction. Here we describe a novel cocaine vaccine employing the mucosal adjuvant and mast cell-activating oligopeptide, mastoparan-7 (M7), to achieve optimal IgA antibody responses in mucosal secretions and effective induction of humoral immunity using a short immunization protocol. This formulation, using a hapten-carrier system to deliver cocaine as antigen, also reduced cocaine penetration of the blood brain barrier and protected mice from its psychoactive effects by reducing cocaine-induced locomotion. Surprisingly, the magnitude of cocaine-specific antibody titers induced by each adjuvant was not the major determinant of functional protection from cocaine challenge. A side-by-side comparison of the two haptens, cocaine and its analog GNC demonstrated that cocaine haptenation resulted in superior functional protection when used in combination with the novel mucosal adjuvant, M7. These results provide a new potential strategy for combatting cocaine addiction through mucosal vaccination.

Travel medicine, coca and cocaine: demystifying and rehabilitating Erythroxylum - a comprehensive review

Few travel health measures are as controversial as the use of coca leaves at high altitude; yet, there appears widespread ignorance among health professionals and the general public about coca, its origins as well as its interesting and often flamboyant history. Equally, the cultural and traditional significance to Andean people is not recognised. The coca leaves contain many alkaloids, one of which, cocaine, has gained notoriety as a narcotic, leading to the mistaken idea that coca equals cocaine. This article contrasts coca with cocaine in an attempt to explain the differences but also the reasons for this widespread misconception. By its very nature, there may never be scientific ‘proof’ that coca leaves do or do not work for travellers at altitude, but at least a solid knowledge of coca, and how it differs from cocaine, provides a platform for informed opinions and appropriate critical views on the current confusing and contradictory legal situation.

Mirtazapine attenuates anxiety- and depression-like behaviors in rats during cocaine withdrawal

BACKGROUND

Anxiety and depression, key symptoms of the cocaine withdrawal syndrome in human addicts, are considered the main factors that precipitate relapse in chronic cocaine addiction. Preclinical studies have found that rodents exposed to different withdrawal periods show an increase in anxiety and depressive-like behavior. Mirtazapine - a tetracyclic medication - is used primarily to treat depression and, sometimes, anxiety. It has also successfully improved withdrawal symptoms in drug-dependent patients.

AIM

This study sought to determine whether chronic dosing of mirtazapine during cocaine withdrawal reduced depression- and anxiety-like behaviors that characterize cocaine withdrawal in animals.

METHODS

Cocaine pre-treated Wistar rats were subjected to a 60-day cocaine withdrawal period during which depression- and anxiety-like behaviors were evaluated in open field tests (OFT), the elevated plus-maze (EPM), the light-dark box test (LDT), the forced swimming test (FST) and spontaneous locomotor activity (SLA).

RESULTS

We found that chronic dosing with different doses of mirtazapine (30 and 60 mg/kg) decreased depression- and anxiety-like behaviors induced by different doses of cocaine (10, 20 and 40 mg/kg) during the 60-day cocaine withdrawal.

INTERPRETATION

Our results suggest that the pharmacological effect of mirtazapine on its target sites of action (α₂-adrenergic and 5-HT_2A and 5-HT₃ receptors) within the brain may improve depression- and anxiety-like behaviors for long periods.

CONCLUSION

Therefore, the findings support the use of mirtazapine as a potentially effective therapy to reduce anxiety and depressive-like behavior during cocaine withdrawal.

Drug-induced stress responses and addiction risk and relapse

A number of studies have assessed the effects of psychoactive drugs on stress biology, the neuroadaptations resulting from chronic drug use on stress biology, and their effects on addiction risk and relapse. This review mainly covers human research on the acute effects of different drugs of abuse (i.e., nicotine, cannabis, psychostimulants, alcohol, and opioids) on the hypothalamic-pituitary-adrenal (HPA) axis and the autonomic nervous system (ANS) responses. We review the literature on acute peripheral stress responses in naïve or light recreational users and binge/heavy or chronic drug users. We also discuss evidence of alterations in tonic levels, or tolerance, in the latter relative to the former and associated changes in the phasic stress responses. We discuss the impact of the stress system tolerance in heavy users on their response to drug- and stress-related cue responses and craving as compared to control subjects. A summary is provided of the effects of glucocorticoid responses and their adaptations on brain striatal and prefrontal cortices involved in the regulation of drug seeking and relapse risk. Finally, we summarize important considerations, including individual difference factors such as gender, co-occurring drug use, early trauma and adversity and drug use history and variation in methodologies, that may further influence the effects of these drugs on stress biology.

The Stimulant Selective Severity Assessment: A replication and exploratory extension of the Cocaine Selective Severity Assessment

BACKGROUND

Cocaine and methamphetamine have similar withdrawal symptoms and many individuals concurrently use both substances; however, no measures concurrently assess withdrawal from multiple stimulants.

OBJECTIVES

This study's aim was to explore the Stimulant Selective Severity Assessment (SSSA), a modified version of the Cocaine Selective Severity Assessment (CSSA), in a sample of stimulant users to determine if it can assess withdrawal symptoms in users of one or more stimulants.

METHODS

Baseline data were analyzed from the STimulant Reduction Intervention using Dosed Exercise trial, a multisite randomized clinical trial that evaluated exercise versus health education on drug use outcomes in individuals with stimulant use disorders. Data were analyzed for internal consistency, construct validity, and scale dimensionality.

RESULTS

Internal consistency for the full sample was good (α = 0.81; N = 302), with similar alphas in Cocaine (0.81; n = 177) and Cocaine/Other Stimulant (0.82; n = 92) groups, but with much lower alpha for the group without cocaine use (Other Stimulant, i.e., primarily methamphetamine, α = 0.66; n = 32). Support for construct validity was evidenced by significant positive correlations (r = 0.17 to 0.67) with measures of stimulant craving, depressive symptoms, and pain. Four factors were revealed. Conclusions/Importance: The Stimulant Selective Severity Assessment is a new measure that can be used to assess withdrawal symptoms in users of cocaine or cocaine plus methamphetamine, but it should not be administered to users of methamphetamine only.

Bioavailability and Pharmacokinetics of Oral Cocaine in Humans

The pharmacokinetic profile of oral cocaine has not been fully characterized and prospective data on oral bioavailability are limited. A within-subject study was performed to characterize the bioavailability and pharmacokinetics of oral cocaine. Fourteen healthy inpatient participants (six males) with current histories of cocaine use were administered two oral doses (100 and 200 mg) and one intravenous (IV) dose (40 mg) of cocaine during three separate dosing sessions. Plasma samples were collected for up to 24 h after dosing and analyzed for cocaine and metabolites by gas chromatography-mass spectrometry. Pharmacokinetic parameters were calculated by non-compartmental analysis, and a two-factor model was used to assess for dose and sex differences. The mean ± SEM oral cocaine bioavailability was 0.32 ± 0.04 after 100 and 0.45 ± 0.06 after 200 mg oral cocaine. Volume of distribution (Vd) and clearance (CL) were both greatest after 100 mg oral (Vd = 4.2 L/kg; CL = 116.2 mL/[min kg]) compared to 200 mg oral (Vd = 2.9 L/kg; CL = 87.5 mL/[min kg]) and 40 mg IV (Vd = 1.3 L/kg; CL = 32.7 mL/[min kg]). Oral cocaine area-under-thecurve (AUC) and peak concentration increased in a dose-related manner. AUC metabolite-to-parent ratios of benzoylecgonine and ecgonine methyl ester were significantly higher after oral compared to IV administration and highest after the lower oral dose. In addition, minor metabolites were detected in higher concentrations after oral compared to IV cocaine. Oral cocaine produced a pharmacokinetic profile different from IV cocaine, which appears as a rightward and downward shift in the concentration-time profile. Cocaine bioavailability values were similar to previous estimates. Oral cocaine also produced a unique metabolic profile, with greater concentrations of major and minor metabolites.

Modulation of drug choice by extended drug access and withdrawal in rhesus monkeys: Implications for negative reinforcement as a driver of addiction and target for medications development

Chronic drug exposure is hypothesized to recruit negative reinforcement processes that increase the magnitude and alter the mechanisms of drug reinforcement. Candidate substrates of negative reinforcement include increased signaling via stress-related neurotransmitters such as corticotropin releasing factor (CRF, acting at CRF receptors) or dynorphin (acting at kappa opioid receptors) and/or decreased signaling via reward-related neurotransmitters such as dopamine. Determinants of drug reinforcement can be examined with choice procedures, in which subjects choose between a drug of interest (e.g. heroin or cocaine) and a non-drug alternative reinforcer (e.g. food). This review summarizes evidence collected from studies of drug choice in rhesus monkeys to address the negative reinforcement hypothesis. In monkeys choosing between heroin and food, chronic heroin exposure and subsequent withdrawal produces a robust increase in heroin choice. This withdrawal-associated increase in heroin choice is blocked by morphine and by other mu opioid agonists used to treat opioid use disorder (methadone, buprenorphine); however, withdrawal-associated increases in heroin choice are not reliably blocked by antagonists of CRF or kappa opioid receptors or by an indirect dopamine agonist. In monkeys choosing between cocaine and food, chronic cocaine exposure and withdrawal fail to increase cocaine choice or alter sensitivity of cocaine choice to treatment with candidate therapeutics including an indirect dopamine agonist and a kappa opioid receptor antagonist. These results support a role for negative reinforcement in self-administration of heroin but not cocaine. The constellation of neurobiological changes that constitutes the negative reinforcing stimulus in opioid-dependent rhesus monkeys remains to be determined.

Exposure of adolescent mice to 3,4-methylenedioxypyrovalerone increases the psychostimulant, rewarding and reinforcing effects of cocaine in adulthood

BACKGROUND AND PURPOSE

3,4-Methylenedioxypyrovalerone (MDPV) is a synthetic cathinone with powerful psychostimulant effects. It selectively inhibits the dopamine transporter (DAT) and is 10-50-fold more potent as a DAT blocker than cocaine, suggesting a high abuse liability. The main objective of the present study was to assess the consequences of an early (adolescence) MDPV exposure on the psychostimulant, rewarding and reinforcing effects induced by cocaine in adult mice.

EXPERIMENTAL APPROACH

Twenty-one days after MDPV pretreatment (1.5 mg·kg^-1 , s.c., twice daily for 7 days), adult mice were tested with cocaine, using locomotor activity, conditioned place preference and self-administration (SA) paradigms. In parallel, dopamine D₂ receptor density and the expression of c-Fos and ΔFosB in the striatum were determined.

KEY RESULTS

MDPV treatment enhanced the psychostimulant and conditioning effects of cocaine. Acquisition of cocaine SA was unchanged in mice pretreated with MDPV, whereas the breaking point achieved under a progressive ratio programme and reinstatement after extinction were higher in this group of mice. MDPV decreased D₂ receptor density but increased ΔFosB expression three-fold. As expected, acute cocaine increased c-Fos expression, but MDPV pretreatment negatively influenced its expression. ΔFosB accumulation declined during MDPV withdrawal, although it remained elevated in adult mice when tested for cocaine effects.

CONCLUSION AND IMPLICATIONS

MDPV exposure during adolescence induced long-lasting adaptive changes related to enhanced responsiveness to cocaine in the adult mice that seems to lead to a higher vulnerability to cocaine abuse. This particular behaviour correlated with increased expression of ΔFosB.

Acute withdrawal-related hypophagia elicited by amphetamine is attenuated by pretreatment with selective dopamine D1 or D2 receptor antagonists in rats

After receiving 2.0mg/kg amphetamine, rats show two phases of reduced food intake, short-term hypophagia, during the first several hours after treatment, and longer-term hypophagia, approximately 19 to 26 h after treatment. The longer-term hypophagia may be an indicator of an acute withdrawal. This study assessed whether D1 and D2 receptor activation were important early events in the elicitation of longer-term hypophagia. Throughout a series of five-day tests, rats could lever press for food pellets for one-hour periods beginning every 3h. On test day 1, rats were given a saline pretreatment, and 15 min later they were given a saline treatment. On test day 3, they were given a pretreatment of either saline or a selective dopamine receptor antagonist, and 15 min later they were given a treatment of either saline or amphetamine (2.0mg/kg). In Experiment 1, pretreatments included 3, 12, 31, and 50 μg/kg of the selective D1 receptor antagonist SCH 23390. In Experiment 2, pretreatments included 25, 50, and 100 μg/kg of the selective D2 receptor antagonist eticlopride. Distance moved was monitored for the first 6h following pretreatment-treatment combinations to obtain an indirect behavioral measure of receptor blockade (antagonist attenuation of amphetamine hyperactivity). Food intake at each meal opportunity was monitored throughout each five day test. Patterns of food intake following day 1 saline-saline and day 3 pretreatment-treatment were compared. The combination saline-amphetamine produced short-term and longer-term hypophagia. Combinations involving antagonist-saline did not produce longer-term changes in food intake. Pretreatment with 12 to 50 μg/kg of SCH 23390 produced substantial blockade of amphetamine hyperactivity and prevented amphetamine-induced acute-withdrawal-related longer-term hypophagia. Eticlopride produced a partial blockade of longer-term hypophagia. Both D1 and D2 receptor activation are required for full expression of longer-term hypophagia following amphetamine administration.

Psychedelic symptoms of cannabis and cocaine use as a function of trait impulsivity

Trait impulsivity has been linked to addiction in humans. It has been suggested that drug users with high trait impulsivity levels are more sensitive to subjective drug intoxication. This study assessed whether subjective response to drugs differs between drug users with normal or high levels of trait impulsivity. Regular drug users (N = 122) received doses of cocaine HCl, cannabis, and placebo in a three-way crossover study. Their mood, dissociative state, and psychedelic symptoms were measured with subjective rating scales (CADDS, Bowdle, POMS). Trait impulsivity was assessed with the Barratt Impulsiveness Scale. Cannabis increased dissociation and psychedelic state, as well as fatigue, confusion, depression and anxiety, and decreased arousal, positive mood, vigor, friendliness, and elation. Cocaine increased dissociation, psychedelic state, vigor, friendliness, elation, positive mood, anxiety and arousal, while decreasing fatigue. Only a few subjective items revealed a drug × trait impulsivity interaction, suggesting that psychedelic symptoms were most intense in high impulsivity subjects. Trait impulsiveness ratings were negatively correlated with ratings of vigor (r = -.197) and positively correlated with ratings of loss of thought control (r = .237) during cannabis intoxication. It is concluded that a broad association between trait impulsivity and psychedelic subjective drug experience appears to be absent.

Emerging drugs for the treatment of cocaine use disorder: a review of neurobiological targets and pharmacotherapy

INTRODUCTION

Cocaine use is a global public health concern of significant magnitude, negatively impacting both the individual as well as larger society. Despite numerous trials, the discovery of an effective medication for treatment of cocaine use disorder remains elusive.

AREAS COVERED

This article reviews the emerging pharmacotherapies for treatment of cocaine use disorder, focusing on those medications that are currently in Phase II or III human clinical trials. Articles reviewed were obtained through searches of PubMed, Ovid MEDLINE, Clinicaltrials.gov and the Pharmaprojects database.

EXPERT OPINION

Research into cocaine pharmacotherapy must continue to show innovation. Given that medications targeting single neurotransmitter systems have demonstrated little efficacy in treatment of cocaine use disorder, the recent focus on pharmacotherapeutic agents with multiple neurobiochemical targets represents an exciting shift in trial design and approach. Additionally, consideration of pharmacogenetics may be helpful in identification of subpopulations of cocaine-dependent individuals who may preferentially respond to medications.

Chronic cocaine causes long-term alterations in circadian period and photic entrainment in the mouse

The disruptive effects of cocaine on physiological, behavioral and genetic processes are well established. However, few studies have focused on the actions of cocaine on the adult circadian timekeeping system, and none have explored the circadian implications of long-term (weeks to months) cocaine exposure. The present study was undertaken to explore the actions of such long-term cocaine administration on core circadian parameters in mice, including rhythm period, length of the nocturnal activity period and photic entrainment. For cocaine dosing over extended periods, cocaine was provided in drinking water using continuous and scheduled regimens. The impact of chronic cocaine on circadian regulation was evidenced by disruptions of the period of circadian entrainment and intrinsic free-running circadian period. Specifically, mice under a skeleton photoperiod (1-min pulse of dim light delivered daily) receiving continuous ad libitum cocaine entrained rapidly to the light pulse at activity onset. Conversely, water controls entrained more slowly at activity offset through a process of phase-delays, which resulted in their activity rhythms being entrained 147° out of phase with the cocaine group. This pattern persisted after cocaine withdrawal. Next, mice exposed to scheduled daily cocaine presentations exhibited free-running periods under constant darkness that were significantly longer than water controls and which also persisted after cocaine withdrawal. These cocaine-induced perturbations of clock timing could produce chronic psychological and physiological stress, contributing to increased cocaine use and dependence.

Vaccines against stimulants: cocaine and MA

While the worldwide prevalence of cocaine use remains significant, medications, or small molecule approaches, to treat drug addictions have met with limited success. Anti-addiction vaccines, on the other hand, have demonstrated great potential for treating drug abuse using a distinctly different mechanism of eliciting an antibody response that blocks the pharmacological effects of drugs. We provide a review of vaccine-based approaches to treating stimulant addictions; specifically and cocaine addictions. This selective review article focuses on the one cocaine vaccine that has been into clinical trials and presents new data related to pre-clinical development of a methamphetamine (MA) vaccine. We also review the mechanism of action for vaccine induced antibodies to abused drugs, which involves kinetic slowing of brain entry as well as simple blocking properties. We present pre-clinical innovations for MA vaccines including hapten design, linkage to carrier proteins and new adjuvants beyond alum. We provide some new information on hapten structures and linkers and variations in protein carriers. We consider a carrier, outer membrance polysaccharide coat protein (OMPC), that provides some self-adjuvant through lipopolysaccharide components and provide new results with a monophosopholipid adjuvant for the more standard carrier proteins with cocaine and MA. The review then covers the clinical trials with the cocaine vaccine TA-CD. The clinical prospects for advances in this field over the next few years include a multi-site cocaine vaccine clinical trial to be reported in 2013 and phase 1 clinical trials of a MA vaccine in 2014.

Psychometric properties of the Spanish version of the Cocaine Selective Severity Assessment to evaluate cocaine withdrawal in treatment-seeking individuals

Reliable and valid assessment of cocaine withdrawal is relevant for treating cocaine-dependent patients. This study examined the psychometric properties of the Spanish version of the Cocaine Selective Severity Assessment (CSSA), an instrument that measures cocaine withdrawal. Participants were 170 cocaine-dependent inpatients receiving detoxification treatment. Principal component analysis revealed a 4-factor structure for CSSA that included the following components: 'Cocaine Craving and Psychological Distress', 'Lethargy', 'Carbohydrate Craving and Irritability', and 'Somatic Depressive Symptoms'. These 4 components accounted for 56.0% of total variance. Internal reliability for these components ranged from unacceptable to good (Chronbach's alpha: 0.87, 0.65, 0.55, and 0.22, respectively). All components except Somatic Depressive Symptoms presented concurrent validity with cocaine use. In summary, while some properties of the Spanish version of the CSSA are satisfactory, such as interpretability of factor structure and test-retest reliability, other properties, such as internal reliability and concurrent validity of some factors, are inadequate.

Abstinence-related changes in sleep during treatment for cocaine dependence

BACKGROUND

Former sleep studies among non-treatment seeking chronic cocaine users had captured polysomnographic changes for as long as three weeks of abstinence.

METHODS

20 cocaine dependent participants, randomized to placebo in an ongoing clinical trial, received 12 days of inpatient substance abuse treatment followed by 6 weeks of outpatient cognitive behavioral therapy. Polysomnographic recording was performed on consecutive nights during the 1st and 2nd inpatient and 3rd and 6th outpatient weeks. Number of days abstinent was determined from thrice weekly urine toxicology and self-report. Polysomnographic sleep was compared between study week 1 and 2, using paired t-tests. Trajectory of total sleep time (TST) was modeled both as a linear and a quadratic function of days abstinent.

RESULTS

Despite reporting an improvement in overall sleep quality, polysomnographic sleep worsened from week 1 to 2. Among all participants, TST and stage 2 sleep time decreased, while REM sleep latency increased. Among participants who began the study with a positive urine test, there was also a decrease in REM and a trend for decreased slow wave sleep. TST compared to number of days abstinent (up to 54 days) was best fit with a quadratic model (p=0.002), suggesting the possibility of an improvement in total sleep time with extended abstinence.

CONCLUSIONS

This is the first polysomnographic characterization of sleep in a large sample of cocaine users in treatment. Present findings confirm earlier results of poor and deteriorating sleep early in abstinence, and raise the possibility of improvement after an extended abstinence.

Hyperactivation of the cognitive control network in cocaine use disorders during a multisensory Stroop task

BACKGROUND

It has been suggested that individuals with cocaine use disorders (chronic cocaine abusers, CCA) have impairments in cognitive control, which likely contribute to impairments in decision making around drug use and relapse. However, deficits in cognitive control have currently only been studied under conditions of unisensory stimulation, which may not be reflective of more realistic multisensory drug cues.

METHODS

The current study employed functional magnetic resonance imaging (fMRI) to measure neuronal activity during a multisensory numeric Stroop task.

RESULTS

Despite few differences in reaction time, recently abstinent CCA (N=14) exhibited increased activation in prefrontal cortex, striatum and thalamus during cognitive control relative to a group of carefully matched controls (N=16). Importantly, these neuronal differences were relatively robust in classifying patients from controls (approximately 90% accuracy) and evident during conditions of both low (slow stimulus presentation rate) and relatively high (faster stimulus presentation rate) cognitive demand. In addition, CCA also failed to deactivate the default-mode network during high frequency visual trials.

CONCLUSIONS

In summary, current results indicate compensatory activation within the cognitive control network in recently abstinent CCA to achieve similar levels of behavioral performance.

Cocaine hydrolase gene therapy for cocaine abuse

Rapid progress in the past decade with re-engineering of human plasma butyrylcholinesterase has led to enzymes that destroy cocaine so efficiently that they prevent or interrupt drug actions in the CNS even though confined to the blood stream. Over the same time window, improved gene-transfer technology has made it possible to deliver such enzymes by endogenous gene transduction at high levels for periods of a year or longer after a single treatment. This article reviews recent advances in this field and considers prospects for development of a robust therapy aimed at aiding recovering drug users avoid addiction relapse.

Immunotherapy for drug abuse

Substance use disorders continue to be major medical and social problems worldwide. Current medications for substance use disorders have many limitations such as cost, availability, medication compliance, dependence, diversion of some to illicit use and relapse to addiction after discontinuing their use. Immunotherapies using either passive monoclonal antibodies or active vaccines have distinctly different mechanisms and therapeutic utility from small molecule approaches to treatment. They have great potential to help the patient achieve and sustain abstinence and have fewer of the above limitations. This review covers the cocaine vaccine development in detail and provides an overview of directions for developing anti-addiction vaccines against the abuse of other substances. The notable success of the first placebo-controlled clinical trial of a cocaine vaccine, TA-CD, has led to an ongoing multi-site, Phase IIb clinical trial in 300 subjects. The results from these trials are encouarging further development of the cocaine vacine as one of the first anti-addiction vaccines to go forward to the U.S. Food and Drug Administration for review and approval for human use.

Enhanced cue reactivity and fronto-striatal functional connectivity in cocaine use disorders

Chronic cocaine use is associated with enhanced cue reactivity to drug stimuli. However, it may also alter functional connectivity (fcMRI) in regions involved in processing drug stimuli. Our aims were to evaluate the neural regions involved in subjective craving and how fcMRI may be altered in chronic cocaine users. Fourteen patients with a confirmed diagnosis of cocaine abuse or dependence (CCA) and 16 gender, age, and education-matched healthy controls (HC) completed a cue reactivity task and a resting state scan while undergoing functional magnetic resonance imaging. CCA showed increased activation compared to HC in left dorsolateral prefrontal and bilateral occipital cortex in response to cocaine cues but not to appetitive control stimuli. Moreover, CCA also showed increased activation within the orbital frontal cortex (OFC) for cocaine cues relative to the appetitive stimuli during a hierarchical regression analysis. A negative association between subjective craving and activity in medial posterior cingulate gyrus (PCC) was also observed for CCA. CCA exhibited increased resting state correlation (positive) between cue-processing seed regions (OFC and ventral striatum), and negative connectivity between cue-processing regions and PCC/precuneus. These alterations in fcMRI may partially explain the neural basis of increased drug cue salience in CCA.

Increased non-rapid eye movement sleep by cocaine withdrawal: possible involvement of A2A receptors

This study attempted to clarify whether cocaine withdrawal altered sleep architecture and the role of adenosine receptors in this process. Cocaine (20 mg/kg) was administered subcutaneously once per day for 7 days to rat implanted with sleep/wake recording electrode. Polygraphic signs of undisturbed sleep/wake activities were recorded for 24 h before cocaine administration (basal recording as control); withdrawal-day 1 (after 1 day of repeated cocaine administration), withdrawal-day 8 (after 8 days of repeated cocaine administration), and withdrawal-day 14 (after 14 days of repeated cocaine administration), respectively. On cocaine withdrawal-day 1, wakefulness was significantly increased, total sleep was decreased, non-rapid eye movement sleep was markedly reduced, and rapid eye movement sleep was enhanced. Sleep/wake cycles were also increased on cocaine withdrawal day 1. However, non-rapid eye movement sleep was increased on withdrawal-day 8 and 14, whereas rapid eye movement sleep was decreased and no significant changes were observed in the total sleep and sleep/wake cycles during these periods. Adenosine A(2A) receptors expression was increased on withdrawal-day 8 and 14, whereas A(1) receptors levels were reduced after 14 days of withdrawal and the A(2B) receptors remained unchanged. Our findings suggest that alterations of sleep and sleep architecture during cocaine subacute and subchronic withdrawals after repeated cocaine administration may be partially involved in A(2A) receptors over-expression in the rat hypothalamus.

Antipsychotic agents for the treatment of substance use disorders in patients with and without comorbid psychosis

Substance dependence has serious negative consequences upon society such as increased health care costs, loss of productivity, and rising crime rates. Although there is some preliminary evidence that atypical antipsychotic agents may be effective in treating substance dependence, results have been mixed, with some studies demonstrating positive and others negative or no effect. The present study was aimed at determining whether this disparity originates from that reviewers separately discussed trials in patients with (DD) and without (SD) comorbid psychosis. Using electronic databases, we screened the relevant literature, leaving only studies that used a randomized, double-blind, placebo-controlled or case-control design that had a duration of 4 weeks or longer. A total of 43 studies were identified; of these, 23 fell into the category of DD and 20 into the category of SD. Studies in the DD category suggest that atypical antipsychotic agents, especially clozapine, may decrease substance use in individuals with alcohol and drug (mostly cannabis) use disorders. Studies in the SD category suggest that atypical antipsychotic agents may be beneficial for the treatment of alcohol dependence, at least in some subpopulations of alcoholics. They also suggest that these agents are not effective at treating stimulant dependence and may aggravate the condition in some cases.

The concept of pharmacologic cocaine interception as a treatment for drug abuse

Cocaine access to brain tissue and associated cocaine-induced behaviors are substantially reduced in rats and mice by significant plasma levels of an enzyme that rapidly metabolizes the drug. Similar results have been obtained in rodents and humans with therapeutic anti-cocaine antibodies, which sequester the drug and prevent its entry into the brain. We show that an efficient cocaine hydrolase can lead to rapid unloading of anti-cocaine antibodies saturated with cocaine, and we provide a theoretical basis for the hypothesis that dual therapy with antibody and hydrolase enzyme may be especially effective.

Cocaine-induced breakdown of the blood-brain barrier and neurotoxicity

Role of cocaine in influencing blood-brain barrier (BBB) function is still unknown. Available evidences suggest that cocaine administration results in acute hyperthermia and alterations in brain serotonin metabolism. Since hyperthermia is capable to induce the breakdown of the BBB either directly or through altered serotonin metabolism, a possibility exists that cocaine may induce neurotoxicity by causing BBB disruption. This hypothesis is discussed in this review largely based on our own laboratory investigations. Our observations in rats demonstrate that cocaine depending on the dose and routes of administration induces profound hyperthermia, increased plasma and brain serotonin levels leading to BBB breakdown and brain edema formation. Furthermore, cocaine was able to enhance cellular stress as seen by upregulation of heat shock protein (HSP 72 kD) expression and resulted in marked neuronal and glial cell damages at the time of the BBB dysfunction. Taken together, these observations are the first to suggest that cocaine-induced BBB disruption is instrumental in precipitating brain pathology. The possible mechanisms of cocaine-induced BBB breakdown and neurotoxicity are discussed.