Effects of phencyclidine on 5-hydroxytryptophan- and suckling-induced prolactin release

Abstract

The effects of acute and chronic exposure to phencyclidine (PCP) on the regulation of prolactin (PRL) secretion were examined. Female Sprague-Dawley rats were injected with PCP (10 mg/kg) or saline for 14 days, or just prior to the administration of the serotonin precursor, 5-hydroxytryptophan (5-HTP). A single injection of PCP had no effect on the 5-HTP-induced rise of plasma PRL levels. In contrast, chronic administration of PCP facilitated the release of PRL induced by 5-HTP. Peak plasma PRL levels were more than 3-fold higher after chronic PCP. The acute effect of PCP on suckling-induced PRL release was also examined. PCP delayed the rise of plasma PRL levels by suckling. The magnitude and profile of PRL, however, were similar to saline controls. The pups of PCP-treated dams failed to obtain milk during the suckling episode. Exogenous oxytocin restored the milk ejection reflex in PCP-treated dams. PCP had no effect on basal PRL release from anterior pituitary cells in vitro, and failed to alter the effects of TRH or dopamine. Conclusions: (1) chronic, but not acute, administration of PCP facilitates the 5-HTP-induced release of PRL, (2) acute exposure to PCP delays the suckling-induced rise in PRL and appears to inhibit oxytocin release. These data demonstrate that both acute and chronic PCP may alter the regulation of PRL release, likely through an indirect central mechanism.