The influence of some central nervous system (CNS) active drugs on pituitary growth hormone (GH) content and on insulininduced GH release was investigated. GH was assayed by the “tibia test” method. Chlorpromazine (CPZ), reserpine and α-ethyltryptamine (Monase) were able to suppress the release of GH induced by 2 U/kg of insulin. High doses of reserpine induced GH release. Other CNS-active drugs, i.e., pentobarbital, morphine, desmethylimipramine, d-amphetamine and iproniazid, were unable to block the release of GH induced by insulin. Increase of pituitary GH was noticed after administration of D-amphetamine. The suppressive action of CPZ and reserpine appeared to be exerted on CNS and not on the pituitary, since rats pretreated with these drugs showed a normal depletion of pituitary GH content after administration of rat hypothalamic extracts. The block of insulin-induced GH release effected by CPZ, reserpine and Monase drugs with marked stressinhibitory activity suggested that insulin might act as a stress to release GH. Consequently, pituitary GH content was determined after application of various stresses. Very large doses of vasopressin, epinephrine, urecholine, or exposure to cold caused depletion of pituitary GH. Suppression of insulin-induced GH release was finally obtained by the administration of dexamethasone. The hypothesis is proposed that, in the rat, the decrease of pituitary GH observed after insulin administration may reflect a nonspecific stress effect of the hypoglycemic stimulus. (Endocrinology80:109,1967)
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Müller et al. (1967) studied this question.