The Role of Dopamine in Seizure-Induced Prolactin Release in Humans

Prolactin (PRL) plasma levels rise severalfold following spontaneous or electrically induced seizures. To assess the role of dopamine in this neuroendocrine response, we studied the effect of electroconvulsive therapy (ECT) on plasma PRL after maximal dopamine receptor blockade induced by intravenous metoclopramide. Six patients undergoing ECT received metoclopramide or placebo, in counterbalanced order, 30 min prior to application of the electrical stimulus. Blood samples were obtained at - 15 min, immediately before, and at 15 min intervals for 1 h after the treatment. Under placebo conditions, PRL plasma levels increased nearly sevenfold in response to ECT. The administration of metoclopramide produced a large increase in PRL plasma levels, with no further increase in PRL concentrations after ECT. The data suggest that the PRL plasma rise after ECT involves dopamine as it is not seen when the dopaminergic inhibitory tone, exerted by the hypothalamus on the pituitary lactotroph, has been removed.