Expression of salt hunger in hypophysectomized rats

Hypophysectomized and pituitary-intact rats were tested for their expression of salt hunger under a variety of experimental conditions. The results show that hypophysectomized rats ingest less salt in response to salt hunger induced by sodium depletion, captopril or angiotensin in comparison to pituitary-intact rats. In contrast, both groups ingest the same amount of salt in response to mineralocorticoid-induced salt hunger. While sodium excretion and plasma sodium levels were comparable in the two groups, the angiotensinogen mRNA was reduced by hypophysectomy in several limbic brain regions as well as in the liver. These results suggest that reduced salt intake in response to manipulations of the body sodium and renin-angiotensin system in hypophysectomized rats may result from decreased angiotensinogen mRNA levels.