EFFECT OF THE DOPAMINE RECEPTOR BLOCKING AGENT PIMOZIDE ON THE GROWTH HORMONE RESPONSE TO ARGININE AND EXERCISE AND ON THE SPONTANEOUS GROWTH HORMONE FLUCTUATIONS

Abstract

Pimozide, a specific blocker of dopamine receptors, was administered orally to lo diabetics for 2 days before an arginine-hydrochioride i n fusion. In 8 healthy volunteers and 2o diabetics exercise tests on a bicycle ergometer were performed with a load of loo Watts and 5o Watts respectively without or after a single dose of pimozide 3o min before the test. In 4 male diabeticsday profiles of growth hormone (GH) were estimated without and during treatment with pimozide for 4 days. The arginine and exercise induced GH release was found to be significantly lowered by pimozide, whereas the marked spontaneous fluctuations in the diabetics were even enhanced by pimozide. These data support the concept of the involvement of dopaminergic stimulation in the response of GH to arginine and exercise. The spontaneous fluctuations of GH, however, seem to be regulated by other neuroendocrine mechanisms.