[Effect of cyproheptadine on the regulation of the adrenal system (author's transl)]

The effect of the antiserotoninergic agent cyproheptadine (C) on the adrenal system was studied in male rats, the adrenocorticol function of which was assessed by analysis of the urinary excretion of free corticosterone. After a feeding period with 0.5--0.7 mg C/kg body weight/day for several months significant differences in the urinary excretion of free corticosterone were only found when the rats were exposed to systemic stress stimuli as cold (increase from 118.7 +/- 5.3 to 305.5 +/- 5.1 vs. 417.8 +/- 48.6 ng/d in the controls; p less than 0.001) and hunger (no increase of free corticosterone in treated animals as compared to an increase to 446.0 +/- 53.6 ng/d in the controls). In contrast to these findings no effect of C was seen when studying the neurotropic stress stimuli reserpine and ether. The same was true when measuring free corticosterone under basal conditions and after ACTH- or metyrapone stimulation. It is concluded that serotonin plays a major role as hypothalamic neurotransmitter in systemic but not in the studied neurotropic stress stimuli. The site of serotonin action does not comprise adrenal synthesis of steroids and the hypothalamic-pituitary-adrenal feedback system, as is shown by the ACTH- and metyrapone stimulation tests.