Effect of benztropine on the diurnal prolactin responses to haloperidol.

Prolactin (PRL) responses to haloperidol were investigated at 0900 and 1800 h in six young healthy men under basal conditions and after benztropine mesylate administration. Haloperidol administration induced significantly higher PRL release during the evening compared to the morning. The anticholinergic drug, benztropine, potentiated the PRL responses to haloperidol both in the morning and in the evening. The possible mechanisms of these findings are discussed.