Altered emotional states in knockout mice lacking 5-HT1A or 5-HT1B receptors.
Dysfunctions of the serotonergic system have been implicated in a number of psychiatric disorders including depression, anxiety and disorders of impulse control. To model these disorders we have generated mice with altered serotonergic systems. Specifically, we have created mice that lack or express reduced levels of two serotonin receptors: 5-HT1A and 5-HT1B receptors. These receptors are localized both on serotonergic neurons where they act as autoreceptors and on non-serotonergic neurons. As a result, the 5-HT1A and 5-HT1B receptors control the tone of the serotonergic system and mediate some of the postsynaptic effects of serotonin. Agonists of these receptors are currently used in the treatment of migraine and anxiety disorders. Mice lacking these receptors develop, feed, and breed normally and do not display any obvious abnormalities. However, when analyzed in a number of behavioral paradigms, the 5-HT1A and 5-HT1B knockout mice display a number of contrasting phenotypes. While the 5-HT1B knockout mice are more aggressive, more reactive, and less anxious than the wild-types, the 5-HT1A knockouts are less reactive, more anxious, and possibly less aggressive than the wild-types. We are currently investigating with tissue-specific knockout mice which neural circuits are responsible for these phenotypes. (+info)
Group and case study of the dysexecutive syndrome in alcoholism without amnesia.
OBJECTIVES: To test the dysexecutive syndrome (DES) hypothesis of chronic alcoholism by the neuropsychological group and case study approaches. METHODS: A comprehensive neuropsychological assessment, including the "behavioural assessment of dysexecutive syndrome", a battery of tests recently designed to be "ecologically valid", was administered to 17 patients with chronic alcoholism without amnesia to examine executive functions, intelligence, and memory. In terms of each neuropsychological measure, reciprocal analyses of group means and individual case profiles were conducted: for the first contrasting the alcoholic patients with 17 age matched healthy subjects; and for the second making intersubject and intrasubject comparison of the patients, according to percentile basis impairment indices obtained from the control subjects. RESULTS: Despite relatively unimpaired memory and intelligence, the patients as a whole had the impairment of a wide range of executive domains, extending to "everyday" problem solving as well as more elementary aspects of executive functions, such as visuospatial performance, mental set shifting, and the inhibition of habitual behaviour. The profile analysis divided individual patients into four groups: the representative DES characterised by a clear dissociation between impaired executive functions and preserved intelligence and memory; the group of a modified dysexecutive pattern in which memory as well as executive functions were impaired with intelligence preserved; the group of general cognitive deterioration; and the group of unimpaired cognitive functioning. About two thirds of the patients were categorised into either the first or the second type of DES. CONCLUSION: DES characterised by the even more pronounced impairment of executive functions than of intelligence and memory afflicts a considerable proportion of patients with chronic alcoholism. Due to its subtlety, this would be potentially left out, unless appropriate behavioural measures were administered. This condition may prevent patients with alcoholism from achieving full recovery and benefiting from rehabilitation. (+info)
A procedure to teach self-control to children with attention deficit hyperactivity disorder.
This study examined the use of a progressive delay procedure combined with verbal mediation to teach self-control to children with attention deficit disorder. Results showed that when participants were initially given the choice between an immediate smaller reinforcer and a larger delayed reinforcer, all participants chose the smaller reinforcer. When slight delays to obtain a larger reinforcer were instated in conjunction with intervening verbal activity, all participants demonstrated self-control regardless of the content of the verbal activity. (+info)
Identifying problem and compulsive gamblers.
OBJECTIVE: To present a meta-analysis of current research on the prevalence, identification, and treatment of problem and compulsive gamblers. QUALITY OF EVIDENCE: Problem and compulsive gambling was not a socio-scientific concern until the last two decades. Hence research on this topic is limited. The summary and analysis for this paper relied on computer searches of journal and news abstracts in addition to direct contact with organizations addressing the identification and treatment of compulsive gamblers. MAIN MESSAGE: An estimated 5% of those who gamble run into problems. About 1% of those who gamble are predicted to experience serious problems. Successful treatment of problem and compulsive gambling continues to be a challenge. Although cognitive therapy has been the favoured approach, a combination of several therapeutic approaches is advocated. CONCLUSIONS: Problem and compulsive gambling can present a real health threat. As with other addictions, treatment strategies continue to be a baffling social problem. Aware and informed physicians can have a pivotal role in the difficult process of identifying, acknowledging, and remediating problem and compulsive gambling. (+info)
Effects of clozapine and typical antipsychotic drugs on plasma 5-HT turnover and impulsivity in patients with schizophrenia: a cross-sectional study.
OBJECTIVE: To compare the efficacy of clozapine with typical antipsychotic drugs in controlling impulsivity and to explore the possible correlation of impulsivity with plasma 5-hydroxytryptamine (5-HT) levels, plasma 5-hydroxyindoleacetic acid (5-HIAA) levels and plasma 5-HT turnover. DESIGN: Prospective, cross-sectional study open to medication and blinded to biochemical analyses. PARTICIPANTS: Healthy control subjects (n = 24) and 46 inpatients and outpatients meeting the DSM-IV criteria for schizophrenia; 20 were being treated with clozapine and 26 were taking typical antipsychotic drugs. INTERVENTIONS: All psychotropic drugs other than clozapine or typical antipsychotic drugs were discontinued for at least 5 days and subjects fasted overnight before they were assessed. OUTCOME MEASURES: Coccaro Impulsivity Scale scores, plasma 5-HT levels, 5-HIAA levels and 5-HT turnover. RESULTS: Patients treated with clozapine and those treated with typical antipsychotics had significantly higher impulsivity scores than the control group, and the mean impulsivity score of the typical antipsychotic group was significantly higher than that of patients treated with clozapine. The mean concentration of 5-HT of the typical antipsychotic group was significantly lower than that of the control group and patients treated with clozapine; however, mean plasma levels of 5-HIAA were significantly higher for the clozapine group than the other 2 groups. 5-HT turnover was significantly higher for the 2 drug-treatment groups than for the control group. CONCLUSIONS: These results suggest that treatment with clozapine should be considered for patients with schizophrenia who are impulsive and aggressive. (+info)
Effects of prenatal exposure to marijuana.
QUESTION: I am treating a 27-year-old woman who is now in her 10th week of pregnancy. She smokes marijuana two to three times a week, but does not use other drugs. She also smokes 20 cigarettes a day. I am concerned about the effects of marijuana exposure on her baby. ANSWER: It is not always possible to isolate the effect of marijuana exposure from other possible confounders on pregnancy outcome. Although marijuana is not an established human teratogen, recent well conducted studies suggest it might have subtle negative effects on neurobehavioural outcomes, including sleep disturbances, impaired visual problem solving, hyperactivity, impassivity, inattention, and increased delinquency. (+info)
Deficits in impulse control associated with tonically-elevated serotonergic function in rat prefrontal cortex.
Converging lines of evidence suggest that dysfunction of brain serotonergic systems may underlie impulsive behavior. However, the nature of this deficit remains poorly understood because indirect indices of serotonin (5-HT) function are often used in clinical and experimental studies. In this investigation we measured 5-HT release directly in the prefrontal cortex of rats using in vivo microdialysis during performance of a visual attentional task. A number of performance measures were taken, including the number of premature responses made during the inter-trial interval before the onset of the visual discriminanda. This form of behavioral disinhibition was defined as impulsive, after. Lengthening the inter-trial interval increased the sensitivity of the task for detecting impulsive tendencies. Cortical levels of 5-HT and its metabolite 5-HIAA remained at pre-task levels over 1 h of task performance. By contrast, levels of dopamine (DA) and its metabolite DOPAC increased during this period. Regression analysis established a positive relationship between premature (impulsive) responses and 5-HT efflux, both under basal (r = 0.49) and task-related (r = 0.42) conditions (n = 31). No such relationship was found for prefrontal levels of DA. However, post-mortem analysis revealed that animals that were more impulsive had a higher turnover of DA in anterior cingulate, prelimbic and infralimbic cortices but no detectable abnormalities in 5-HT function. These data indicate that elevated 5-HT release in the prefrontal cortex may underlie deficits in impulse control on this task. Additionally, DA dysfunction in this region may be another, possibly independent, trait marker of impulsivity. (+info)
Evidence for a dysfunctional prefrontal circuit in patients with an impulsive aggressive disorder.
Humans with lesions to the orbital/medial prefrontal cortex and interconnected areas display impulsive aggressive behavior. To examine further the relationship between impulsive aggression and orbital/medial prefrontal dysfunction, we measured the behavioral performance of psychiatric patients with a disorder characterized by impulsive aggression, Intermittent Explosive Disorder (IED). Presently, no evidence exists for a localized brain lesion in IED subjects. However, on the basis of the location of brain lesions that produce acquired impulsive aggression, we hypothesized that IED subjects would exhibit test performance similar to patients with lesions to the orbital/medial prefrontal cortex. Subjects with IED and controls were administered three tests sensitive to lesions of the orbital/medial prefrontal circuit: the Iowa Gambling Task, facial emotion recognition, and odor identification, and two control tests of working memory. On the gambling task, IED subjects continued to make disadvantageous decisions throughout the 100 trials, whereas controls learned to avoid disadvantageous decisions. On the facial recognition test, IED subjects were impaired at recognizing "anger," "disgust," and "surprise," and they were biased to label neutral faces with "disgust" and "fear." On odor identification, IED subjects were mildly anosmic and were impaired relative to controls. However, on the working memory control tests, both groups performed similarly. Across tests, the performance of IED subjects resembles the performance of patients with orbital/medial prefrontal lesions in previous studies. These results extend the link between dysfunction of the orbital/medial prefrontal circuit and impulsive aggressive behavior. (+info)