Objective: To determine the role of dopamine and 5-hydroxytryptamine (5-HT; serotonin) in the reinforcing effects of alcohol and apomorphine.
Design: Experimental study.
Place and duration of study: Department of Biochemistry, University of Karachi from September to November 2004.
Subjects and methods: The study was conducted on 24 male albino Wistar rats. Reinforcing effects were monitored in a conditioned place preference (CPP) paradigm using a light-dark activity box. Slicing and punching method was used to collect dorsal and ventral striatum. Neurochemical estimations were done by HPLC-EC.
Results: Withdrawal from repeated administration of ethanol (1g/kg/day) as well as apomorphine (1 mg/kg/day) elicited reinforcement that could be monitored in a CPP paradigm. CNS depressant effects of ethanol were not altered on repeated administration but CNS stimulatory effects of apomorphine increased. Reinforcing effects of ethanol but not apomorphine were associated with a decrease in dopamine metabolism in the ventral striatum.
Conclusion: A decrease in the activity of dopaminergic neurons following withdrawal from repeated administration is involved in the compulsive use of abused drugs.