THE NOVEL VASOACTIVE HORMONE, ADRENOMEDULLIN, INHIBITS WATER DRINKING IN THE RAT

The novel hormone, adrenomedullin (AdM), which exerts potent hypotensive effects in the periphery and natriuretic actions in the kidney, was found to be antidipsogenic. Cerebroventricular injection of AdM (22, 44, and 88 pmol) resulted in a dose-related diminution of water drinking in response to subsequent central administration of 100 pmol angiotensin If. Additionally, 88 pmol AdM significantly inhibited the drinking response to overnight water deprivation and hyperosmotic challenge. No significant effects of AdM in the doses tested were observed on blood pressure, heart rate, or motor activity. These results suggest that this novel hormone can act within the nervous system to complement its peripheral actions on fluid and electrolyte homeostasis, independent of a central action on cardiovascular function or locomotion.