Effects of Hypothalamic Surgery and Somatostatin on Chlorpromazine-Induced Growth Hormone Release in Rats

Abstract

Intravenous injection of chlorpromazine (100, 200, 500 µ.g/100 g body wt) produced a significant dose-related increase in plasma immunoreactive growth hormone (GH) in intact rats, in which basal plasma GH levels were low and stable under urethane anesthesia. Basal plasma GH levels were significantly elevated in rats with complete hypothalamic deafferentation or anterior hypothalamic cut, whereas there was no significant rise in plasma GH in rats with a posterior hypothalamic cut. Increases in plasma GH induced by chlorpromazine (200 µg/100 g body wt iv) were also observed in rats with complete deafferentation, or anterior or posteriorcuts of the hypothalamus. Chlorpromazine did not cause any significant increments in plasma GH in rats with extensive hypothalamic destruction. Synthetic somatostatin (5 µg/100 g body wt iv) significantly suppressed plasma GH response to chlorpromazine (100 µg/100 g body wt iv). These results suggest that rat GH release can be stimulated by chlorpromazine influencing the hypo...