Relationship of disinhibition and aggression to blunted prolactin response to meta-chlorophenylpiperazine in cocaine-dependent patients

International Union of Basic and Clinical Pharmacology. CX. Classification of Receptors for 5-hydroxytryptamine; Pharmacology and Function

5-HT receptors expressed throughout the human body are targets for established therapeutics and various drugs in development. Their diversity of structure and function reflects the important role 5-HT receptors play in physiologic and pathophysiological processes. The present review offers a framework for the official receptor nomenclature and a detailed understanding of each of the 14 5-HT receptor subtypes, their roles in the systems of the body, and, where appropriate, the (potential) utility of therapeutics targeting these receptors. SIGNIFICANCE STATEMENT: This review provides a comprehensive account of the classification and function of 5-hydroxytryptamine receptors, including how they are targeted for therapeutic benefit.

A short history of the 5-HT2C receptor: from the choroid plexus to depression, obesity and addiction treatment

This paper is a personal account on the discovery and characterization of the 5-HT_2C receptor (first known as the 5-HT_1C receptor) over 30 years ago and how it translated into a number of unsuspected features for a G protein-coupled receptor (GPCR) and a diversity of clinical applications. The 5-HT_2C receptor is one of the most intriguing members of the GPCR superfamily. Initially referred to as 5-HT_1CR, the 5-HT_2CR was discovered while studying the pharmacological features and the distribution of [³H]mesulergine-labelled sites, primarily in the brain using radioligand binding and slice autoradiography. Mesulergine (SDZ CU-085), was, at the time, best defined as a ligand with serotonergic and dopaminergic properties. Autoradiographic studies showed remarkably strong [³H]mesulergine-labelling to the rat choroid plexus. [³H]mesulergine-labelled sites had pharmacological properties different from, at the time, known or purported 5-HT receptors. In spite of similarities with 5-HT₂ binding, the new binding site was called 5-HT_1C because of its very high affinity for 5-HT itself. Within the following 10 years, the 5-HT_1CR (later named 5-HT_2C) was extensively characterised pharmacologically, anatomically and functionally: it was one of the first 5-HT receptors to be sequenced and cloned. The 5-HT_2CR is a GPCR, with a very complex gene structure. It constitutes a rarity in the GPCR family: many 5-HT_2CR variants exist, especially in humans, due to RNA editing, in addition to a few 5-HT_2CR splice variants. Intense research led to therapeutically active 5-HT_2C receptor ligands, both antagonists (or inverse agonists) and agonists: keeping in mind that a number of antidepressants and antipsychotics are 5-HT_2CR antagonists/inverse agonists. Agomelatine, a 5-HT_2CR antagonist is registered for the treatment of major depression. The agonist Lorcaserin is registered for the treatment of aspects of obesity and has further potential in addiction, especially nicotine/ smoking. There is good evidence that the 5-HT_2CR is involved in spinal cord injury-induced spasms of the lower limbs, which can be treated with 5-HT_2CR antagonists/inverse agonists such as cyproheptadine or SB206553. The 5-HT_2CR may play a role in schizophrenia and epilepsy. Vabicaserin, a 5-HT_2CR agonist has been in development for the treatment of schizophrenia and obesity, but was stopped. As is common, there is potential for further indications for 5-HT_2CR ligands, as suggested by a number of preclinical and/or genome-wide association studies (GWAS) on depression, suicide, sexual dysfunction, addictions and obesity. The 5-HT_2CR is clearly affected by a number of established antidepressants/antipsychotics and may be one of the culprits in antipsychotic-induced weight gain.

Incubation of cocaine cue reactivity associates with neuroadaptations in the cortical serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system

Intensification of craving elicited by drug-associated cues during abstinence occurs over time in human cocaine users while elevation of cue reactivity ("incubation") is observed in rats exposed to extended forced abstinence from cocaine self-administration. Incubation in rodents has been linked to time-dependent neuronal plasticity in the medial prefrontal cortex (mPFC). We tested the hypothesis that incubation of cue reactivity during abstinence from cocaine self-administration is accompanied by lower potency and/or efficacy of the selective serotonin (5-HT) 5-HT2C​ receptor (5-HT2CR) agonist WAY163909 to suppress cue reactivity and a shift in the subcellular localization profile of the mPFC 5-HT2CR protein. We observed incubation of cue reactivity (measured as lever presses reinforced by the discrete cue complex) between Day 1 and Day 30 of forced abstinence from cocaine relative to sucrose self-administration. Pharmacological and biochemical analyses revealed that the potency of the selective 5-HT2CR agonist WAY163909 to suppress cue reactivity, the expression of synaptosomal 5-HT2CR protein in the mPFC, and the membrane to cytoplasmic expression of the 5-HT2CR in mPFC were lower on Day 30 vs. Day 1 of forced abstinence from cocaine self-administration. Incubation of cue reactivity assessed during forced abstinence from sucrose self-administration did not associate with 5-HT2CR protein expression in the mPFC. Collectively, these outcomes are the first indication that neuroadaptations in the 5-HT2CR system may contribute to incubation of cocaine cue reactivity.

Distress Tolerance: Associations With Posttraumatic Stress Disorder Symptoms Among Trauma-Exposed, Cocaine-Dependent Adults

The present investigation examined associations between distress tolerance and posttraumatic stress disorder (PTSD) symptoms in a cocaine-dependent sample. Participants were comprised of 138 cocaine-dependent adults (Mage = 45.4, SD = 9.9; 81% male; 76.3% African American) who endorsed trauma exposure, defined according to Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR) PTSD Criterion A. Participants were administered interview-based measures and completed a series of self-report questionnaires. Results indicated that distress tolerance was significantly, incrementally (negatively) associated with PTSD symptom severity, contributing 6.8% of unique variance to the model (p < .001); notably, the overall model explained 44.8% of variance in PTSD symptomatology. Distress tolerance also contributed between 2.7% and 6.8% of unique variance across each of the PTSD symptom clusters (ps < .05). Incremental effects were documented, after accounting for the variance explained by theoretically relevant covariates (i.e., gender, cocaine-use severity, depressive symptoms, trauma-exposure severity). Theoretical and clinical implications are discussed.

Factors associated with physical or sexual intimate partner violence perpetration by men attending substance misuse treatment in Catalunya: A mixed methods study

BACKGROUND

Prevalence of intimate partner violence perpetration is higher among male substance misusers than men in the general population. Previous studies have included few risk factors, limiting their capacity to inform interventions.

AIM

The aim of this study was to examine factors associated with intimate partner violence by male substance misusers.

METHODS

Two hundred and thirty-five men in treatment for substance misuse completed surveys that included the Revised Conflict Tactics Scale and the Psychological Maltreatment of Women Inventory (PMWI). Variables significant in bivariate analyses were entered into multiple logistic regression analyses. Seventeen in-depth interviews were conducted with perpetrators and analysed using a framework approach.

RESULTS

Just over a third of the men (34%) had been violent in the last year to their current/most recent partner. After excluding the men's own domestic victimisation from the multivariate model, perpetratation of such violence was significantly and independently associated with lower level of education, having higher PMWI dominance-isolation and emotional-verbal subscale scores and parents who had separated/divorced, and at a lower level of significance, childhood physical abuse, hazardous drinking and cocaine as the principal drug for which treatment was sought. Interview data suggested that perpetrators 'blamed' alcohol or cocaine use, jealousy, control and provocation or 'fighting back' for their behaviour.

CONCLUSIONS

Intimate partner violence is common among men attending substance misuse treatment. Integrated interventions should that address both intimate partner violence and substance misuse should be considered. Areas for intervention would include reducing dominating-isolating behaviours and emotional-verbal abuse, improving communication skills, challenging gender-specific roles and believing that substance use 'causes' violent behaviour.

Variation within the serotonin (5-HT) 5-HT₂C receptor system aligns with vulnerability to cocaine cue reactivity

Cocaine dependence remains a challenging public health problem with relapse cited as a major determinant in its chronicity and severity. Environmental contexts and stimuli become reliably associated with its use leading to durable conditioned responses ('cue reactivity') that can predict relapse as well as treatment success. Individual variation in the magnitude and influence of cue reactivity over behavior in humans and animals suggest that cue-reactive individuals may be at greater risk for the progression to addiction and/or relapse. In the present translational study, we investigated the contribution of variation in the serotonin (5-HT) 5-HT2C receptor (5-HT2CR) system in individual differences in cocaine cue reactivity in humans and rodents. We found that cocaine-dependent subjects carrying a single nucleotide polymorphism (SNP) in the HTR2C gene that encodes for the conversion of cysteine to serine at codon 23 (Ser23 variant) exhibited significantly higher attentional bias to cocaine cues in the cocaine-word Stroop task than those carrying the Cys23 variant. In a model of individual differences in cocaine cue reactivity in rats, we identified that high cocaine cue reactivity measured as appetitive approach behavior (lever presses reinforced by the discrete cue complex) correlated with lower 5-HT2CR protein expression in the medial prefrontal cortex and blunted sensitivity to the suppressive effects of the selective 5-HT2CR agonist WAY163909. Our translational findings suggest that the functional status of the 5-HT2CR system is a mechanistic factor in the generation of vulnerability to cocaine-associated cues, an observation that opens new avenues for future development of biomarker and therapeutic approaches to suppress relapse in cocaine dependence.

Serotonin at the nexus of impulsivity and cue reactivity in cocaine addiction

Cocaine abuse and addiction remain great challenges on the public health agendas in the U.S. and the world. Increasingly sophisticated perspectives on addiction to cocaine and other drugs of abuse have evolved with concerted research efforts over the last 30 years. Relapse remains a particularly powerful clinical problem as, even upon termination of drug use and initiation of abstinence, the recidivism rates can be very high. The cycling course of cocaine intake, abstinence and relapse is tied to a multitude of behavioral and cognitive processes including impulsivity (a predisposition toward rapid unplanned reactions to stimuli without regard to the negative consequences), and cocaine cue reactivity (responsivity to cocaine-associated stimuli) cited as two key phenotypes that contribute to relapse vulnerability even years into recovery. Preclinical studies suggest that serotonin (5-hydroxytryptamine; 5-HT) neurotransmission in key neural circuits may contribute to these interlocked phenotypes well as the altered neurobiological states evoked by cocaine that precipitate relapse events. As such, 5-HT is an important target in the quest to understand the neurobiology of relapse-predictive phenotypes, to successfully treat this complex disorder and improve diagnostic and prognostic capabilities. This review emphasizes the role of 5-HT and its receptor proteins in key addiction phenotypes and the implications of current findings to the future of therapeutics in addiction. This article is part of a Special Issue entitled 'NIDA 40th Anniversary Issue'.

Integrated Treatment for Substance Abuse and Partner Violence (I-StoP)

Substance use disorders and intimate partner violence (IPV) perpetration frequently co-occur, and it has been hypothesized that alcohol use and IPV perpetration are causally related. This led to the development of an Integrated treatment for Substance abuse and Partner violence (I-StoP). This case study describes the treatment of Henry, who repeatedly abused his partner and was diagnosed with alcohol and cannabis dependence. Treatment with I-StoP was highly successful with respect to IPV: At posttreatment and 6 months follow-up, no IPV had taken place. However, Henry had not changed substance use. This can be explained by the spurious model that states that a third variable, such as inadequate problem-solving skills (which was addressed in I-StoP), may be responsible for both IPV and substance abuse. In addition, Henry’s partner was involved in treatment and became more assertive and, in contrast, he did change substance use. This case study illustrates that IPV is a very complex problem and that it is important to involve the partner.

Revisiting the serotonin-aggression relation in humans: a meta-analysis

The inverse relation between serotonin and human aggression is often portrayed as "reliable," "strong," and "well established" despite decades of conflicting reports and widely recognized methodological limitations. In this systematic review and meta-analysis, we evaluate the evidence for and against the serotonin deficiency hypothesis of human aggression across 4 methods of assessing serotonin: (a) cerebrospinal fluid levels of 5-hydroxyindoleacetic acid (CSF 5-HIAA), (b) acute tryptophan depletion, (c) pharmacological challenge, and (d) endocrine challenge. Results across 175 independent samples and over 6,500 total participants were heterogeneous, but, in aggregate, revealed a small, inverse correlation between serotonin functioning and aggression, anger, and hostility (r = -.12). Pharmacological challenge studies had the largest mean weighted effect size (r = -.21), and CSF 5-HIAA studies had the smallest (r = -.06). Potential methodological and demographic moderators largely failed to account for variability in study outcomes. Notable exceptions included year of publication (effect sizes tended to diminish with time) and self- versus other-reported aggression (other-reported aggression was positively correlated to serotonin functioning). We discuss 4 possible explanations for the pattern of findings: unreliable measures, ambient correlational noise, an unidentified higher order interaction, and a selective serotonergic effect. Finally, we provide 4 recommendations for bringing much needed clarity to this important area of research: acknowledge contradictory findings and avoid selective reporting practices; focus on improving the reliability and validity of serotonin and aggression measures; test for interactions involving personality and/or environmental moderators; and revise the serotonin deficiency hypothesis to account for serotonin's functional complexity.

The comparative effectiveness of Integrated treatment for Substance abuse and Partner violence (I-StoP) and substance abuse treatment alone: a randomized controlled trial

BACKGROUND

Research has shown that treatments that solely addressed intimate partner violence (IPV) perpetration were not very effective in reducing IPV, possibly due to neglecting individual differences between IPV perpetrators. A large proportion of IPV perpetrators is diagnosed with co-occurring substance use disorders and it has been demonstrated that successful treatment of alcohol dependence among alcohol dependent IPV perpetrators also led to less IPV. The current study investigated the relative effectiveness of Integrated treatment for Substance abuse and Partner violence (I-StoP) to cognitive behavioral treatment addressing substance use disorders including only one session addressing partner violence (CBT-SUD+) among patients in substance abuse treatment who repeatedly committed IPV. Substance use and IPV perpetration were primary outcome measures.

METHOD

Patients who entered substance abuse treatment were screened for IPV. Patients who disclosed at least 7 acts of physical IPV in the past year (N = 52) were randomly assigned to either I-StoP or CBT-SUD+. Patients in both conditions received 16 treatment sessions. Substance use and IPV perpetration were assessed at pretreatment, halfway treatment and posttreatment in blocks of 8 weeks. Both completers and intention-to-treat (ITT) analyses were performed.

RESULTS

Patients (completers and ITT) in both conditions significantly improved regarding substance use and IPV perpetration at posttreatment compared with pretreatment. There were no differences in outcome between conditions. Completers in both conditions almost fully abstained from IPV in 8 weeks before the end of treatment.

CONCLUSIONS

Both I-StoP and CBT-SUD+ were effective in reducing substance use and IPV perpetration among patients in substance abuse treatment who repeatedly committed IPV and self-disclosed IPV perpetration. Since it is more cost and time-effective to implement CBT-SUD+ than I-StoP, it is suggested to treat IPV perpetrators in substance abuse treatment with CBT-SUD+.

Serotonin function in pathological gambling: blunted growth hormone response to sumatriptan

Pathological gambling is a disruptive behaviour and an important public health concern that is classified as an impulse control disorder, and is also conceptualized as a prototype of 'behavioural addiction'. Its phenomenology cannot be reduced to a single neurobiological dysfunction; instead, it has been conceived as a complex chain of events in which the serotonergic system (5-HT) has often been suggested as one of the most prominent involved. Acute administration of Sumatriptan, a selective 5-HT(1B/1D) agonist, has been used to investigate the functional responsivity of 5-HT(1B/1D) receptors in alcoholics, resulting in a blunted growth hormone response. These findings have been interpreted as being due to the down-regulation of these receptors. However, previous studies could not rule out the possibility that the changes in receptor function were induced by chronic substance exposure. Twenty-two pathological gamblers and 19 healthy control subjects were evaluated in response to double-blind administration of both a single dose of oral Sumatriptan (100 mg) and of placebo in a crossover design. All participants were screened to ensure that they were negative for lifetime alcohol and drug addiction, and had been free of substance abuse for at least 6 months. Outcome measures included growth hormone, prolactin, gambling severity, mood, craving and 'high' change scales. A blunted growth hormone response was observed in pathological gamblers compared with healthy controls after Sumatriptan administration. No statistically significant differences were found for prolactin or behavioural measures, except for an increase in anxiety over time in pathological gamblers. These results, together with those obtained in our previous serotoninergic challenge study, document the presence of a serotonergic dysfunction in pathological gamblers similar to that reported in alcoholics.

Alterations in tryptophan and purine metabolism in cocaine addiction: a metabolomic study

BACKGROUND

Mapping metabolic "signatures" can provide new insights into addictive mechanisms and potentially identify biomarkers and therapeutic targets.

OBJECTIVE

We examined the differences in metabolites related to the tyrosine, tryptophan, purine, and oxidative stress pathways between cocaine-dependent subjects and healthy controls. Several of these metabolites serve as biological indices underlying the mechanisms of reinforcement, toxicity, and oxidative stress.

METHODS

Metabolomic analysis was performed in 18 DSM-IV-diagnosed cocaine-dependent individuals with at least 2 weeks of abstinence and ten drug-free controls. Plasma concentrations of 37 known metabolites were analyzed and compared using a liquid chromatography electrochemical array platform. Multivariate analyses were used to study the relationship between severity of drug use [Addiction Severity Index (ASI) scores] and biological measures.

RESULTS

Cocaine subjects showed significantly higher levels of n-methylserotonin (p < 0.0017) and guanine (p < 0.0031) and lower concentrations of hypoxanthine (p < 0.0002), anthranilate (p < 0.0024), and xanthine (p < 0.012), compared to controls. Multivariate analyses showed that a combination of n-methylserotonin and xanthine contributed to 73% of the variance in predicting the ASI scores (p < 0.0001). Logistic regression showed that a model combining n-methylserotonin, xanthine, xanthosine, and guanine differentiated cocaine and control groups with no overlap.

CONCLUSIONS

Alterations in the methylation processes in the serotonin pathways and purine metabolism seem to be associated with chronic exposure to cocaine. Given the preliminary nature and cross-sectional design of the study, the findings need to be confirmed in larger samples of cocaine-dependent subjects, preferably in a longitudinal design.

Evaluation of heterogeneity in pharmacotherapy trials for drug dependence: a Bayesian approach

AIMS

Difficulty identifying effective pharmacotherapies for cocaine dependence has led to suggestions that subgroup differences may account for some of the heterogeneity in treatment response. Well-attested methodological difficulties associated with these analyses recommend the use of Bayesian statistical reasoning for evaluation of salient interaction effects.

METHODS

A secondary data analysis of a previously published, double-blind, randomized controlled trial examines the interaction of decision-making, as measured by the Iowa Gambling Task, and citalopram in increasing longest sustained abstinence from cocaine use.

RESULTS

Bayesian analysis indicated that there was a 99% chance that improved decision-making enhances response to citalopram. Given the strong positive nature of this finding, a formal, quantitative Bayesian approach to evaluate the result from the perspective of a skeptic was applied.

CONCLUSIONS

Bayesian statistical reasoning provides a formal means of weighing evidence for the presence of an interaction in scenarios where conventional, Frequentist analyses may be less informative. [Supplementary materials are available for this article. Go to the publisher's online edition of The American Journal of Drug and Alcohol Abuse for the following free supplemental resource: Appendix 1].

Blockade of the serotonin 5-HT2A receptor suppresses cue-evoked reinstatement of cocaine-seeking behavior in a rat self-administration model

The serotonin 5-HT2A receptor (5-HT-sub(2A)R) may play a role in reinstatement of drug-seeking. This study investigated the ability of a selective 5-HT-sub(2A)R antagonist to suppress reinstatement evoked by exposure to cues conditioned to cocaine self-administration. Cocaine self-administration (0.75 mg/kg/0.1 mL/6 s infusion; FR 4) was trained in naïve, free-fed rats to allow interpretation of results independent from changes related to food deprivation stress. Pretreatment with the selective 5-HT-sub(2A)R antagonist M100907 (volinanserin) failed to reduce rates of operant responding for cocaine infusions. On the other hand, M100907 (0.001-0.8 mg/kg ip) significantly suppressed the cue-induced reinstatement of cocaine-seeking behavior following extinction; effective M100907 doses did not alter operant responding for cues previously associated with sucrose self-administration. Importantly, a greater magnitude of active lever presses on the initial extinction session (high extinction responders) predicted the maximal susceptibility to M100907-induced suppression of cue-evoked reinstatement. The findings indicate that blockade of the 5-HT-sub(2A)R attenuates the incentive-motivational effects of cocaine-paired cues, particularly in high extinction responders, and suggests that M100907 may afford a therapeutic advance in suppression of cue-evoked craving and/or relapse.

Relationship of the serotonin transporter with prolactin response to meta-chlorophenylpiperazine in cocaine dependence

BACKGROUND

Preclinical evidence indicates that exposure to cocaine influences the activity of the serotonin transporter (5-HTT) as well as several 5-HT receptor subtypes. However, little is known about the relationship between the 5-HTT and 5-HT receptors following cocaine exposure in humans.

OBJECTIVE

We examined the relationship between platelet 5-HTT, a presynaptic 5-HT measure, and prolactin (PRL) response to meta-chlorophenylpiperazine (m-CPP), a postsynaptic 5-HT receptor agonist in cocaine dependent individuals.

METHODS

Platelet [3H] paroxetine binding sites were assayed and the m-CPP challenge test was performed in 35 African American cocaine dependent individuals and 33 controls. Clinical measures included assessments of drug use severity and depression.

RESULTS

Cocaine subjects showed reduced Bmax of [3H] paroxetine (t=4.67, p<0.01) and blunted PRL response to m-CPP (F=21.86, p<0.01) compared to controls. There was a positive correlation between Bmax and delta PRL [peak-baseline PRL] in cocaine subjects (r=0.50, p<0.01) but not in controls (r=0.19). ANCOVA analyses showed that the cocaine subgroup with moderate and severe reduction in Bmax showed a greater blunting in PRL response compared to the subgroup with mild Bmax reductions (F=9.44, p<.005). Multivariate regression models showed that the main effects as well as the interaction of Bmax and severity of cocaine use significantly contributed to impaired PRL response (F=17.90, p<.001).

CONCLUSIONS

Disturbances in serotonin transporter binding and post-synaptic 5-HT receptor function seem to be associated in cocaine-dependent subjects. Severity of cocaine use appears to mediate this relationship. Whether there is a causal association between the two measures, or cocaine has separate and independent pre- and post-synaptic effects needs to be clarified.

Quantitative trait locus analysis identifies rat genomic regions related to amphetamine-induced locomotion and Galpha(i3) levels in nucleus accumbens

Identification of the genetic factors that underlie stimulant responsiveness in animal models has significant implications for better understanding and treating stimulant addiction in humans. F(2) progeny derived from parental rat strains F344/NHsd and LEW/NHsd, which differ in responses to drugs of abuse, were used in quantitative trait locus (QTL) analyses to identify genomic regions associated with amphetamine-induced locomotion (AIL) and G-protein levels in the nucleus accumbens (NAc). The most robust QTLs were observed on chromosome 3 (maximal log ratio statistic score (LRS(max))=21.3) for AIL and on chromosome 2 (LRS(max)=22.0) for Galpha(i3). A 'suggestive' QTL (LRS(max)=12.5) was observed for AIL in a region of chromosome 2 that overlaps with the Galpha(i3) QTL. Novelty-induced locomotion (NIL) showed different QTL patterns from AIL, with the most robust QTL on chromosome 13 (LRS(max)=12.2). Specific unique and overlapping genomic regions influence AIL, NIL, and inhibitory G-protein levels in the NAc. These findings suggest that common genetic mechanisms influence certain biochemical and behavioral aspects of stimulant responsiveness.

Relationship of prolactin response to meta-chlorophenylpiperazine with severity of drug use in cocaine dependence

RATIONALE

Serotonergic (5-HT) mechanisms appear to mediate central effects of cocaine. Therefore 5-HT disturbances could be associated with drug severity.

OBJECTIVES

We investigated whether prolactin (PRL) response to meta-chlorophenylpiperazine (m-CPP), a mixed 5-HT agonist/antagonist were associated with severity of cocaine use.

METHODS

Thirty-six cocaine-dependent subjects and 33 controls underwent a challenge with 0.5 mg/kg of oral m-CPP. Severity of drug use was assessed using the Addiction Severity Index (ASI).

RESULTS

The PRL response to m-CPP was significantly blunted in cocaine patients compared to controls (F = 21.86, p < 0.001). DeltaPRL (peak PRL-baseline PRL) was negatively correlated with ASI-drug (r = -0.45, p < 0.01), ASI-alcohol (r = -0.32, p < 0.05), and ASI-psychological (r = -0.41, p < 0.01) composite scores, and with the quantity, frequency and duration of drug use (r ranged from - 0.41 to - 0.32, p ranged from < 0.01 to 0.05). Hierarchical regressions showed that ASI-drug composite scores significantly predicted the variance in DeltaPRL after controlling for behavioral and demographic variables (F = 4.27, p < 0.05).

CONCLUSIONS

The results indicate that disturbances in 5-HT function as reflected by a blunted response to m-CPP seem to be primarily associated with severity of drug use and to a lesser, although significant extent with behavioral traits in cocaine-dependent patients.