Effect of sulpiride on plasma prolactin in rats.

I.v. injection of sulpiride (S; 0.5-20 mug/100 g b.w.) caused a significant and dose-related increase in plasma prolactin (Prl) levels in urethane-anesthetized rats, with peak values occuring 10 min after the injection. L-dopa administration (2 mg/100 g b.w., i.v.) significantly blunted plasma Prl response to S(1 mug/100 g b.w., i.v.). S injection (1 mug/rat) into a lateral ventricle also raised plasma Prl significantly. Hypothalamic destruction resulted in a prominent increase of basal plasma Prl, which increased further following the injection of S. These results suggest that S stimulates Prl secretion by its possible direct action on the anterior pituitary.