Pharmacological evidence of supersensitivity of central serotonergic receptors involved in the control of prolactin secretion.

m-Chlorophenylpiperazine (m-CPP), a serotonin receptor agonist, induced dose-related increase in plasma prolactin levels in the rat. This effect was significantly prevented by pretreatment with metergoline, a serotonin receptor blocker. Long-term degeneration of hypothalamic serotonin nerve endings induced by intraventricular injection of 5, 7-dihydroxytryptamine, significantly enhanced the PRL-releasing action of m-CPP, as revealed by the shift to the left in the dose-response curve that relates the dose of m-CPP to plasma PRL levels. Thus the evidence suggests the possible development of supersensitivity of central serotonin receptors involved in the control of prolactin release.