INVOLVEMENT OF ANGIOTENSIN IN WATER-INTAKE INDUCED BY PERIPHERAL ADMINISTRATION OF A SEROTONIN AGONIST, 5-CARBOXYAMIDOTRYPTAMINE

Rats were given peripheral injections of a 5HT(1) agonist, 5-carboxy-a midotryptamine (5-CT), and various behavioral, physiological, and neur onal outcomes were documented. 5-CT caused short latency water intake. In rats with a choice between water and hypertonic NaCl, about half o f the rats drank only water while the other half showed an initial rob ust intake of NaCl. Blood pressure was reduced and plasma renin activi ty increased following 5-CT. The effective half life was 1-3 h, with w ater intake inhibiting further consumption. Fos-like immunoreactivity (FLI) was induced by 5-CT in regions of the brain identical to those p reviously shown to be activated by peripheral administration of angiot ensin (Ang) II, The role of endogenously-generated Ang II in the dipso genic action of 5-CT was suggested because captopril inhibited the wat er intake. Possible mechanisms of 5-CT and Ang II-induced thirst are r eviewed, including roles of hypotension and the vagus nerve.