THE EFFECT OF YOHIMBINE, AN ALPHA(2) ADRENERGIC-RECEPTOR ANTAGONIST, ON THE GROWTH-HORMONE RESPONSE TO APOMORPHINE IN NORMAL SUBJECTS

Yohimbine HCl (16 mg po) administered 30 min before clonidine (CLON) ( 2 mu g/kg infused over 10 min) (N = 5) or apomorphine HCl (Ape) (0.5 m g sc) (N = 10) antagonized the growth hormone (GH) response to CLON bu t had no effect on the GH response to Apo in normal men. This finding suggests that in humans, alpha(2) adrenergic mechanisms do not modulat e dopaminergic function, at least not in the hypothalamic-pituitary ax is, and that the GH response to Apo is not mediated via an alpha(2) ad renergic link.