Correlated cholinomimetic-stimulated beta-endorphin and prolactin release in humans.

Previous studies, both in animals and humans, have demonstrated that the intravenous or intraventricular administration of endogenous opioids and opiates produce dose dependent increases in plasma concentrations of prolactin. Notably, in humans, intravenous infusion of centrally active cholinomimetic drugs, such as physostigmine or arecoline, may produce significant increases in plasma concentrations of prolactin and beta-endorphin immunoreactivity. In three separate studies, conducted collaboratively between the National Institute of Mental Health and the University of California at San Diego, physostigmine and arecoline associated increases in plasma concentrations of beta-endorphin immunoreactivity were highly correlated with increases in plasma prolactin concentrations. These results are of interest because centrally active cholinomimetic drugs have been variously reported either to have no effect, to increase, or to inhibit anterior pituitary prolactin release. We propose that cholinergic stimulation of hypothalamic beta-endorphin may represent an interesting example of peptidergic modulation of primary neurochemical effects on hypothalamic-pituitary hormonal regulation.