Domperidone, a peripheral dopamine (DA) receptor blocker which poorly crosses the blood-brain barrier and which is inactive towards dop-amine-sensitive adenylate cyclase, in a dose (100g/kg) sufficient to increase serum prolactin levels at least 5-fold, decreased the growth hormone (GH) response to the DA receptor agonist, apomorphine HC1 (Apo) (0.5 mg s.c.) in each of six normal men examined. The mean GH increment at 30,45, 60 and 75 min following Apo injection, the mean individual peak increment and the mean individual GH secretion (ng min) was significantly decreased by domperidone pretreatment (p<><0.02). these="" results="" indicate="" that="" in="" man="" apo="" stimulates="" gh="" secretion="" by="" an="" effect="" on="" da="" receptors="" which="" are="" not="" linked="" to="" adenylate="" cyclase="" and="" which="" are="" situated="" at="" a="" locus="" in="" the="" hypothalamic-pituitary="" axis="" that="" lies="" outside="" the="" blood-brain="">