Blockade of Release of Growth Hormone by Brain Norepinephrine Depletors

Abstract

Previous studies have shown that reserpine (1 mg/kg ip) completely blocks insulininduced growth hormone (GH) release. The possibility that the suppressive action of this drug on GH secretion might be due to its catecholaminedepleting action was investigated in the present experiments. α-Methyldopa (300 mg/kg ip), amethyl- m-tyrosine (300 mg/kg ip), or tetrabenazine (15 mg/kg ip), like reserpine, were effective in suppressing the release of GH induced by 2 U/kg of insulin. Guanethidine (30 mg/kg ip) and tyramine (15 mg/kg ip) were without effect. The blockade of GH release induced by reserpine (1 mg/kg ip) was reversed by iproniazid (150 mg/kg sc). After reserpine treatment (1 mg/kg ip), the release of growth hormone-releasing factor (GRF) from the hypothalamus induced by insulin (2 U /kg ip) was abolished. From these experiments it is concluded that: 1. The reduction of stores of brain norepinephrine impairs GH release; 2. brain amines might play a role in the release of hypothalamic neurohumoral transmitters. (Endocrinology80: 471, 1967)