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Biomedical subjects

S M Dursun

Publications and source records attributed to S M Dursun.

At least 37 records · Page 2Linked to original sources
PubMed2000

The effects of antipsychotic medication on saccadic eye movement abnormalities in Huntington's disease.

1. The study was a prospective open trial done to determine the effect of antipsychotic medication on saccadic eye movements in patients with Huntington's disease (HD). The authors tested 16 outpatients with HD, 8 of whom were drug free and 8 of whom were on antipsychotic medication. We also tested 24 healthy control subjects. 2. The antisaccade task was used to investigate the voluntary control of saccadic eye movements. Antisaccade latencies and error rates were used as outcome measures. Both HD patient groups showed significantly more antisaccade abnormalities than controls and the rate of abnormalities was very similar between the drug-free and medicated patient groups. 3. The results suggest that these abnormalities are related to underlying neuropathology rather than effects of medication. Either specific dysfunction of the dorsolateral prefrontal cortex or of the subcortical circuit connecting this cortical area to the superior colliculus via the striatum are likely to be responsible for the generation of such antisaccade eye movement abnormalities.

Adult↗
PubMed2000

Blockade of phencyclidine-induced effects by a nitric oxide donor.

1. Phencyclidine (PCP) is widely used as an animal model of schizophrenia. The aim of this study was to better understand the role of nitric oxide (NO) in the mechanism of action of PCP and to determine whether positive NO modulators may provide a new approach to the treatment of schizophrenia. 2. The effects of the NO donor, sodium nitroprusside (SNP), were studied in PCP-treated rats. Following drug administration, behavioural changes and the expression of c-fos, a metabolic marker of functional pathways in the brain, were simultaneously monitored. 3. Acute PCP (5 mg kg(-1), i. p.) treatment induced a complex behavioural syndrome, consisting of hyperlocomotion, stereotyped behaviours and ataxia. Treatment with SNP (2 - 6 mg kg(-1), i.p.) by itself produced no effect on any behaviour studied but completely abolished PCP-induced behaviour in a dose- and time-dependent manner. 4. PCP had differential regional effects on c-fos expression in rat brain, suggesting regionally different patterns of neuronal activity. The most prominent immunostaining was observed in the cortical regions. Pre-treatment with SNP blocked PCP-induced c-fos expression at doses similar to those that suppress PCP-induced behavioural effects. 5. These results implicate the NO system in the mechanism of action of PCP. The fact that SNP abolished effects of PCP suggests that drugs targeting the glutamate-NO system may represent a novel approach to the treatment of PCP-induced psychosis and schizophrenia.

Animals↗
PubMed2000

An exploratory approach to the serotonin syndrome: an update of clinical phenomenology and revised diagnostic criteria.

Serotonin-related adverse side-effects of psychotropic drugs were first recorded in humans in 1960. However, since 1991, these related cases have been diagnosed as 'serotonin syndrome (SS)' according to the criteria reported by Sternbach. In this article, we have reviewed and further explored the validity of these criteria. The clinical profile of 24 cases of the SS published between 1991 and 1995 has been analysed in detail and compared with the symptomatology of 38 previous cases which were also further analysed. Mainly Medline and references from other reports were used to review these cases. The general concept put forward by Sternbach has been approved. On the basis of the severity of overall clinical presentation, it appeared that there is a need to further classify SS into three main groups as: (1) mild state of serotonin-related symptoms; (2) serotonin syndrome (full-blown form); (3) toxic states. Furthermore, the detailed analysis of the SS cases published so far suggests that 'the diagnostic criteria for SS' also require further revision, and these are presented here. We also review, present and discuss the guidelines for the management and treatment of SS.

Humans↗
PubMed2000

Antisaccade eye movement abnormalities in Tourette syndrome: evidence for cortico-striatal network dysfunction?

Saccadic eye movements are rapid eye movements which act to redirect the eyes from one object of interest to another. Accurately and objectively measurable, their underlying neuroanatomical mechanisms have been extensively studied. The antisaccade task allows the study of the frontocortico-striatal network involved in the voluntary control of saccadic eye movements. In this task, the subject is instructed to inhibit a reflex eye movement towards a peripheral target light and, instead, to generate a movement in the equal and opposite direction. An error occurs when the subject fails to suppress reflexive saccades towards the target. Significantly high error rates and increased latencies in the antisaccade task have been reported in disorders associated with dysfunction of the frontocortico-striatal network. Increased saccadic eye movement latencies and error rates have been reported in Tourette syndrome patients (n = 4) who were receiving antipsychotic medication. To investigate this further, we tested the antisaccade task on six male Tourette syndrome patients. The results were compared with 18 age- and sex-matched mentally and physically healthy, medication/alcohol-free controls. Antisaccade latencies were (mean +/- SD; ms) 751.2+/-186.7 for the Tourette syndrome group and 417+/-75.3 for controls, and error rates were 59+/-14.3 for the Tourette syndrome group and 11.9+/-6.4 for controls, respectively. These significant results may further support dysfunction of the frontocortico-striatal network in Tourette syndrome.

Adolescent↗
PubMed2000

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.

Adult↗
PubMed1999

Smoking, nicotine and psychiatric disorders: evidence for therapeutic role, controversies and implications for future research.

Researchers interested in investigating the possible therapeutic effects and the mechanisms of action of nicotine in neuropsychiatric disorders face a social-scientific-ethical dilemma. This dilemma comprises three components: (1) the known addictive potential of nicotine makes careful evaluation of the therapeutic potential of this compound socially unattractive; (2) the potential misuse of scientifically determined data by the tobacco 'lobby' creates ethical concerns; and (3) the possible confusion between the differential effects of nicotine in human smokers versus non-smokers creates difficulties in study designs in voluntary human subjects. Therefore, it is imperative that, at the onset of this review, the authors stress that they do not advocate cigarette-smoking as a route of nicotine intake under any circumstances on the basis that controlled dosing of nicotine may be of potential benefit in some neuropsychiatric disorders. In this article, we review the psychopharmacology of nicotine and its effects in a variety of neuropsychiatric disorders including schizophrenia, depression, anxiety and Tourette's syndrome. Possible mechanisms of action of nicotine directly or indirectly via its interaction with other neurotransmitter systems (i.e. serotonin, dopamine and noradrenaline) in relation to its potential role in these disorders are discussed. It is postulated that new drugs may need to be developed that selectively interact with nicotinic receptors without addiction potential.

Acetylcholine↗
PubMed1999

Effects of amphetamine on saccadic eye movements in man: possible relevance to schizophrenia?

The antisaccade task can be used to test the voluntary control of saccadic eye movements (SEMs). In many disorders with postulated hyperdopaminergic neurotransmission, there are reports of abnormalities in SEMs. To further investigate this, the role of dopamine in SEMs, performance on an antisaccade task was examined in subjects with a history of amphetamine use (a dopamine releaser and reuptake inhibitor). A prospective design was employed in a teaching hospital setting. Six subjects (five males) with a history of amphetamine use were compared to 24 normal controls. None of the subjects were using any other substances, except alcohol and nicotine, as determined by urine screening, which we believe limited the sample size. For subjects who used amphetamine before the task, the presence of amphetamine was confirmed by urinalysis. All subjects completed the antisaccade task. Both error rates and latency rates during the antisaccade task were compared between the amphetamine users and controls. The amphetamine users had significantly increased error rates and latencies. These results may suggest that increased error rates and latencies during antisaccade tasks may be due to increased dopamine transmission, which is similar to the findings in schizophrenia.

Adult↗
PubMed1999

Olanzapine for patients with treatment-resistant schizophrenia: a naturalistic case-series outcome study.

OBJECTIVE: This prospective, consecutive case-series outcome investigation evaluates the effectiveness of olanzapine in 16 patients with treatment-resistant schizophrenia. METHOD: Treatment resistance was defined as nonresponsiveness to at least 3 antipsychotic drugs from at least 2 different chemical classes. A minimum baseline score on the Brief Psychiatric Rating Scale (BPRS) of 45 was required for enrolment. Outcome evaluation measures included the BPRS, Global Assessment Scale (GAS), and Abnormal Involuntary Movement Scale (AIMS). RESULTS: Subjects (n = 16) has a mean age of 40 years and mean duration of illness of 16 years. Olanzapine treatment was initiated at 5 mg daily and was increased based on clinical judgement up to a maximum of 40 mg daily. Significant decreases in mean BPRS (P < 0.001) and GAS (P < 0.01) scores were observed at weeks 4, 8, 12, and 16, compared with baseline. Eight of 16 patients responded to olanzapine, as defined by a 20% decrease in BPRS score by week 16. Dyskinetic movements significantly increased at week 4 (P < 0.01) but did not differ from baseline at weeks 8 and 16. CONCLUSION: These results suggest that olanzapine at moderate to high doses may offer an effective treatment for a significant proportion of patients with schizophrenia nonresponsive to multiple trials of conventional antipsychotics. A randomized controlled trial is encouraged to validate these findings, and comparative trials are required to determine when clinicians should consider this approach.

Adult↗
PubMed1999

Effects of typical antipsychotic drugs and risperidone on the quality of sleep in patients with schizophrenia: a pilot study.

OBJECTIVE: To investigate the effects of a newer antipsychotic drug, risperidone (a potent serotonin 5-HT2A/2C and dopamine D2-receptor blocker), on the quantity and quality of sleep in patients with schizophrenia. DESIGN: Prospective pilot study. SETTING: Outpatient treatment at a mental health hospital. PATIENTS: Two groups of age- and sex-matched patients with schizophrenia receiving either risperidone (n = 8) or a typical antipsychotic drug (n = 8), and a group of age- and sex-matched controls (n = 8). OUTCOME MEASURES: Sleep quality, measured by a visual analogue scale, and sleep continuity, measured using a movement index calculated from actigraph data. RESULTS: Patients with schizophrenia had more disturbed sleep than controls. Compared with patients treated with typical antipsychotic drugs, patients treated with risperidone reported significantly better sleep quantity and quality as well as general functioning. CONCLUSION: Improvement by risperidone may be related to 5-HT2A/2C receptor blockade; however, further controlled studies are required to confirm these results.

Adult↗