Identification of pathways involved in the natriuretic, kaliuretic and diuretic responses induced by cholinergic stimulation of the medial septal area (MSA).

Natriuresis, kaliuresis and diuresis have been studied in rats following water loading and cholinergic stimulation in the MSA before and after bilateral electrolitic lesion of the habenula, or medullary stria, or supraoptic nucleus or paraventricular nucleus, or fornix. Carbachol injection in MSA elicited an increase of natriuresis and kaliuresis. These responses were blocked by bilateral electrolytic lesion of the habenula, medullary stria, or supraoptic nucleus but not of the paraventricular nucleus or the fornix. Urinary output plotted as a function of time showed antidiuresis in periods of 20 and 40 minutes after carbachol injection into the MSA. The lesion of the supraoptic nucleus inhibited this antidiuresis and natriuresis. The lesion of the habenula or medullary stria blocked natriuresis but not antidiuresis suggesting an independence between the mechanisms of antidiuretic hormone release and natriuresis regulation. The integrity of the habenula, medullary stria and supraoptic nucleus seems to be important in the mediation of the natriuretic response induced by carbachol injection into the MSA.