Relationship between Platelet Serotonin Uptake Sites and Measures of Impulsivity, Aggression, and Craving among African-American Cocaine Abusers

Combined use of cocaine and alcohol: A violent cocktail? A systematic review

It is generally believed that the use of alcohol and cocaine alone and especially in combination elicits aggression and violent behaviour. Though there is overwhelming proof that heavy alcohol use is associated with violence, this is not the case for cocaine. Still, in the popular press and by spokesmen of the police, cocaine use is seen as a cause of violent incidents. In the current systematic review, available data from human studies on the relation between cocaine and violent behaviour is presented. In particular, we present scientific data on the acute induction of violence by cocaine alone, as well as, that by the combination of cocaine and alcohol known to be frequently used simultaneously. RESULTS: show that there is only weak scientific evidence for the acute induction of violent behaviour by cocaine, either when used alone or in combination with alcohol. Based on these data we were also able to refute misconceptions about the relation between cocaine and violence published in the popular press and governmental reports, because it appeared that there was hardly any empirical support for this widely shared opinion. Probably, contextual factors, including cocaine use disorder and personality disorder, may better explain the assumed association between cocaine and violence.

Operant novelty seeking predicts cue-induced reinstatement following cocaine but not water reinforcement in male rats

RATIONALE

An important facet of cocaine addiction is a high propensity to relapse, with increasing research investigating factors that predispose individuals toward uncontrolled drug use and relapse. A personality trait linked to drug addiction is high sensation seeking, i.e., a preference for novel sensations/experiences. In an animal model of sensation seeking, operant novelty seeking predicts the acquisition of drug self-administration.

OBJECTIVE

The primary goal of this research was to evaluate the hypothesis that sensitivity to the reinforcing effects of novel sensory stimuli predicts more intensive aspects of drug-taking behaviors, such as relapse.

METHODS

Rats were first tested for Operant Novelty Seeking, during which responses resulted in complex visual/auditory stimuli. Next, rats were trained to respond to water/cocaine reinforcers signaled by a cue light. Finally, rats were exposed to extinction in the absence of discrete cues and subsequently tested in a single session of cue-induced reinstatement, during which active responses resulted in cues previously paired with water/cocaine delivery.

RESULTS

The present study showed operant responses to produce novel sensory stimuli positively correlate with responding for cocaine during self-administration and during discrete cue-induced reinstatement, but no association with performance during extinction. A different pattern of associations was observed for a natural reward, in this case, water reinforcement. Here, the degree of novelty seeking also correlated with responding to water reinforcement and extinction responding; however, operant novelty seeking did not correlate with responding to water cues during testing of cue-induced reinstatement. Taken together, the incongruence of relationships indicates an underlying difference between natural and drug reinforcers.

CONCLUSION

In summary, we found a reinforcer-dependent relationship between operant novelty seeking (i.e., sensation seeking) and responsivity to extinction and discrete cues signaling availability for cocaine (i.e., craving), demonstrating the validity of the operant novelty seeking model to investigate drug seeking and relapse.

Serotonin is the main tryptophan metabolite associated with psychiatric comorbidity in abstinent cocaine-addicted patients

The lack of effective treatments and a high rate of relapse in cocaine addiction constitute a major health problem. The present study was conducted to examine the expression of tryptophan-derived metabolites in the context of cocaine addiction and psychiatric comorbidity, which is common in addicted subjects. Abstinent patients with cocaine use disorder (CUD) and control subjects were recruited for a cross-sectional study. Participants were assessed with a semi-structured diagnostic interview (PRISM) based on DSM-IV-TR for substance and mental disorders. Plasma concentrations of tryptophan metabolites and their association with relevant CUD-related variables and psychiatric comorbidity were explored. We observed decreased plasma kynurenic acid concentrations in the cocaine group, however no associations between CUD-related variables and tryptophan-derived metabolites were found. In contrast, 5-HT concentrations were increased in CUD-patients and the diagnosis of different psychiatric disorders in the cocaine group was related to higher plasma 5-HT concentrations compared with non-comorbid patients. Therefore, while changes in plasma kynurenic acid concentrations appear to be directly associated with lifetime CUD, changes in 5-HT concentrations are associated with psychiatric comorbidity. These results emphasize the need to find potential biomarkers for a better stratification of cocaine-addicted patients in order to develop therapeutic approaches to prevent cocaine relapse.

A comparison of impulsivity, depressive symptoms, lifetime stress and sensation seeking in healthy controls versus participants with cocaine or methamphetamine use disorders

Previous research has focused on developing theories of addiction that may explain behavior in cocaine- and methamphetamine-dependent individuals. The primary goal of this report was to compare and contrast the prevalence of self-reported measures of impulsivity, depression, lifetime stress and sensation-seeking in healthy controls versus individuals with cocaine or methamphetamine use disorders. Twenty-nine individuals with cocaine use disorders and 31 individuals with methamphetamine use disorders were matched with 31 healthy control participants on several demographic variables. All participants were administered behavioral questionnaires including the Barrett Impulsiveness Scale (assessing impulsivity), Beck Depression Inventory II (assessing depression), Life Stressor Checklist-Revised (assessing lifetime stress) and the Impulsive Sensation Seeking Scale (assessing sensation-seeking). When compared to healthy controls, individuals with cocaine and methamphetamine use disorders had significantly higher levels of impulsivity and sensation-seeking. In addition, when compared to healthy controls, individuals with cocaine use disorders had significantly higher Beck Depression Inventory II scores, while individuals with methamphetamine use disorders had significantly higher Life Stressor Checklist-Revised scores. The results revealed that there were significantly higher levels of impulsivity, depression and sensation-seeking in cocaine users and significantly higher impulsivity, lifetime stress and sensation-seeking in methamphetamine users when compared to healthy controls.

Platelet [³H] paroxetine binding in female patients with borderline personality disorder and their sisters

Paroxetine binding could be a vulnerability marker for traits associated with borderline personality disorder (BPD). To study this relationship, we examined [³H] paroxetine binding in female patients with BPD and their sisters. The sample consisted of 54 sibling pairs in which a proband met criteria for BPD. All subjects were given the Diagnostic Interview for Borderlines, revised (DIB-R), the Diagnostic Assessment for Personality Pathology: Brief Questionnaire (DAPP-BQ), the Barratt Impulsivity Scale (BIS), the Affective Lability Scale (ALS), the Hamilton Rating Scale for Anxiety (HAM-A), the Hamilton Rating Scale for Depression (HAM-D), and the Symptom Checklist-90, revised (SCL-90-R). All subjects had platelets assayed for [³H] paroxetine binding. There were no significant differences between probands and sisters, but both groups scored significantly lower than a previously studied control group on B(max). There were no differences on Kd. Neither B(max) nor K(d) was related to most trait or symptomatic measures. Paroxetine binding could reflect endophenotypes common to BPD probands and their first-degree relatives.

Inverse relationship between numbers of 5-HT transporter binding sites and life history of aggression and intermittent explosive disorder

The objective of this study was to determine if platelet 5-HT transporter (5-HTT) sites vary as a function of aggression, and/or impulsiveness, and differ as a function of Intermittent Explosive Disorder (IED). Accordingly, the number of platelet 5-HTT sites was assessed in 100 personality disordered (PD) individuals with varying degrees of aggressiveness. The number of platelet 5-HTT sites was assessed by examining the Bmax of H(3)-Paroxetine Binding to the blood platelet. Life history of aggression was assessed by Life History of Aggression. Impulsivity was assessed by the Barratt Impulsiveness Scale. Diagnoses of IED were made by both DSM-IV and Research Criteria. Examination of the data revealed that Bmax, but not Kd, values of Platelet H(3)-Paroxetine Binding correlated inversely with the LHA Aggression score (r=-.42 n=87, p<.001) but not with the BIS-11 Impulsivity score (r=.03, n=77, p=.777). PD subjects meeting Research Criteria for IED demonstrated a significant reduction in Bmax values for Platelet H(3)-Paroxetine Binding. These results were similar after accounting for the effect of lifetime history of depressive mood disorder on Bmax values for Platelet H(3)-Paroxetine Binding. These data indicate a significant inverse relationship between platelet 5-HTT and aggression, though not impulsivity, as a dimensional variable in personality disordered individuals. Results from the examination of IED as a categorical aggression variable suggest that Research, rather than DSM-IV, criteria better identify individuals with reduced numbers of platelet 5-HTT sites.

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.

Use of stimulants to treat cocaine and methamphetamine abuse

The concept of using stimulants to treat cocaine and methamphetamine dependence is largely based on the "replacement" therapy model that has shown efficacy for treating nicotine and opiate dependence. Although results have been mixed, some evidence supports using stimulant medication to reduce cocaine use. There are not enough data to date to determine the efficacy of stimulants for methamphetamine dependence. Drawbacks of stimulants as treatments include the potential for abuse of the treatment, which necessitates careful screening and monitoring of patients. Possible reasons for efficacy of stimulants include enhancement of monoamine function dysregulated by chronic cocaine or methamphetamine use. Newer medications that enhance dopamine function but lack the abuse potential of older stimulants are being studied. It is hoped that these medications will provide safe, effective treatment for cocaine and methamphetamine dependence, but more research on this topic is needed.

Craving e dependência química: conceito, avaliação e tratamento

O craving ou fissura, cuja definição mais comum é o desejo intenso por uma substância, é um conceito controverso entre os pesquisadores da área da dependência química. OBJETIVO: Realizar revisão teórica a respeito do craving nos bancos de dados PsycInfo, Medline, ProQuest e Science Direct. MÉTODO: As palavras-chave utilizadas foram craving, dependence e drug e o período pesquisado foi entre 1995 e 2007. RESULTADOS: Os resultados demonstraram que são encontrados diversos significados para o craving, alguns se restringindo a desejo, e outros, considerando-o não só como desejo, mas como antecipação do resultado positivo do uso da substância, alívio dos sintomas de abstinência ou afeto negativo e intenção de fumar, o que reflete uma visão multidimensional deste construto. A etiologia do craving pode ser explicada por intermédio dos modelos: comportamental, cognitivo ou psicossocial e neurobiológico, porquanto a opção por um destes influencia a avaliação e o manejo. CONCLUSÃO: Conclui-se quanto à multidimensionalidade do craving e quanto à necessidade de que seja utilizado um modelo biopsicossocial que integre os diversos modelos no tratamento de dependentes químicos. Destaca-se a importância da realização de mais estudos para a compreensão do craving em função deste ser um dos principais riscos de recaída.

Polymorphism in the serotonin transporter gene and moderators of prolactin response to meta-chlorophenylpiperazine in African-American cocaine abusers and controls

Serotonin (5-HT) function is altered in several psychiatric disorders, including cocaine dependence (CD), and its role in impulsive-aggressive behaviors has been widely studied. However, the relationship between psychopathological and behavioral dimensions and mechanisms of 5-HT alterations remains unclear. We investigated the relationship of a polymorphism in the 5' promoter region of the serotonin transporter gene (5-HTTLPR) with prolactin (PRL) response to meta-chlorophenylpiperazine (m-CPP) in a sample of 68 African-American individuals, 35 CD subjects and 33 controls. We also examined whether measures of impulsivity, hostility and sensation seeking influenced the relationship between the 5-HTTLPR polymorphism and PRL response to m-CPP in this sample. Individuals with the SS genotype showed significantly heightened PRL response to the challenge compared with the LL and LS genotypes. No influence of gender or substance abuse condition was observed. Hostility was associated with blunted PRL response in the total sample. Cocaine abuse was the most significant moderator of DeltaPRL (peak PRL-baseline PRL), and the interaction of genetic, behavioral and psychopathological measures helped predict most of the observed DeltaPRL (62.5%). Although these results need replication, variation in the 5-HTTLPR gene appears to influence measures of 5-HT function and interact with disease state and personality dimensions to account for 5-HT disturbances in African-American populations.

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

RATIONALE

Considerable evidence indicates that serotonergic (5-HT) mechanisms may mediate central effects of cocaine, and disinhibition and aggression.

OBJECTIVE

We investigated whether prolactin (PRL) response to meta-chlorophenylpiperazine (m-CPP), a mixed 5-HT agonist/antagonist, differed between abstinent cocaine-dependent patients and controls and whether m-CPP challenge responses were related to measures of disinhibition and aggression.

METHODS

Thirty-five cocaine-dependent African-American subjects who were abstinent for at least 2 weeks and 33 African-American controls underwent assessments of disinhibition and aggression and a challenge with 0.5 mg/kg of oral m-CPP.

RESULTS

The PRL response to m-CPP was compared between cocaine patients and controls and between subgroups categorized high or low based on disinhibition and aggression measures. Hierarchical regressions were used to determine whether behavioral measures predicted deltaPRL (peak PRL-baseline PRL). The PRL response to m-CPP was significantly diminished in cocaine patients compared to controls. The blunting was more robust in cocaine patients with high disinhibition and aggression. Among cocaine patients, the high-disinhibition subgroup showed greater blunting than the low-disinhibition subgroup and there was a trend for the high-aggression subgroup to be more blunted than the low-aggression subgroup. The subgroups of controls did not differ from each other. A combination of disinhibition and aggression measures significantly predicted deltaPRL in cocaine patients.

CONCLUSION

The results indicate that cocaine-dependent patients show disturbances in postsynaptic 5-HT function during early abstinence. It appears that the 5-HT disturbances are more pronounced in the subgroup of cocaine patients with high disinhibition and aggression.

Impaired platelet [3H]paroxetine binding in female patients with borderline personality disorder

RATIONALE

There have been few studies of platelet paroxetine binding in borderline personality disorder (BPD).

OBJECTIVE

Our aim was to determine whether female BPD subjects show abnormalities in platelet paroxetine binding.

METHODS

Twenty-one female BPD subjects and 16 age- and gender-matched normal control subjects were assessed using the following: (1) Diagnostic Interview for Borderlines, Revised, (2) Diagnostic Assessment for Personality Pathology: Brief Questionnaire, and (3) Barratt Impulsivity Scale. Platelets were collected and assayed for platelet paroxetine binding.

RESULTS

Bmax was lower in the BPD group (p < 0.0001), but differences in Kd only reached a trend level. There were no associations with trait dimensions independent of diagnosis.

CONCLUSIONS

Reduced platelet paroxetine binding in female BPD patients may reflect presynaptic serotonin dysfunction.

Differences in platelet serotonin transporter sites between African-American tobacco smokers and non-smokers

RATIONALE

The serotonin transporter (5HTT) regulates the magnitude and duration of serotonergic neurotransmission. Although nicotine and other constituents of tobacco smoke may influence serotonin turnover among animals, few studies have examined whether smoking is associated with alteration in 5HTT in humans.

OBJECTIVE

We investigated whether tobacco smokers and non-smokers differed in platelet tritiated paroxetine binding, a measure of 5HTT sites, and whether severity of nicotine dependence (ND) was related to 5HTT measures.

METHODS

Tritiated paroxetine binding sites on platelets were assayed in 26 African-American smokers and 30 non-smokers. Severity of smoking was assessed using the Fagerstrom Test for Nicotine Dependence (FTND). Relationships between FTND scores and maximum number of transporter sites (B(max)) and affinity constant (K(d)) of paroxetine binding were determined.

RESULTS

B(max) values showed a significant negative correlation with FTND scores (rho=-0.28, P<0.01). Notably, smokers with higher ND had significantly lower B(max) compared to those with lower ND and non-smokers; the latter two groups did not differ in B(max) ( F=3.92, P<0.05). Smokers scored higher on impulsivity than non-smokers, however, behavioral variables did not influence the relationship of smoking with B(max). Age, gender and K(d) values were not associated with smoking or B(max).

CONCLUSIONS

Smoking, in particular higher nicotine dependence, appears to be correlated with decreased density of platelet 5HTT sites in African-Americans. The nature of the relationship and whether similar changes occur in the brain merit further investigation.