PROLACTIN RELEASE BY INTRAVENOUS CIMETIDINE IN MAN: EVIDENCE FOR A SUPRAPITUITARY LOCUS OF ACTION

Abstract

To identify the sites at which cimetidine stimulates prolactin release, the drug was administered i.v. (6 mg/kg body wt) to healthy subjects under basal conditions, during dopamine infusion (1 .mu.g/kg-min for 120 min) and after pretreatment with L-dopa plus carbidopa (250 plus 25 mg every 6 h for 1 day). The serum prolactin response to cimetidine was abolished by dopamine infusion and almost completely suppressed by L-dopa plus carbidopa administration. Apparently the drug acts on the CNS to stimulate prolactin release. Although the mechanism of this action is unclear, it does not seem to depend on an antidopaminergic effect and may be related to blockade of brain H2 histamine receptors.