Effects of single and long-term administration of sulpiride on open-field and stereotyped behavior of rats.

1. The effects of single (3.0 to 180.0 mg/kg) and long-term (up to 90.0 mg/kg) administration of sulpiride on open-field and apomorphine-induced stereotyped behavior of rats were studied. 2. When animals were studied 30 min after ip sulpiride administration, locomotion and rearing frequencies in the open-field or apomorphine effects were not modified in a dose-dependent and consistent way by the single sulpiride administration. 3. In relation to control values, a significant decrease in apomorphine-induced stereotyped behavior was observed when rats were injected with a single sulpiride dose 2.5, 5.0, 7.5 and 10.0 h before the dopaminergic agonist. 4. Withdrawal from long-term ip sulpiride administration (up to 90.0 mg/kg per injection, twice daily for 57 days) induced a significant increase in all parameters of activity recorded in the open-field, and the responsiveness to apomorphine was also augmented in sulpiride-withdrawn rats. 5. These results suggest that sulpiride, a benzamide drug that differs from classic neuroleptic agents by producing fewer extrapyramidal side effects, also induces supersensitivity of central dopaminergic receptors.