The Role of Mineralocorticoid Receptor of the Nucleus Tractus Solitarius on Driving Salt Intake.

The purpose of this study was to determine if neurons within the NTS that possess the mineralocorticoid receptor (MR) and the enzyme 11-β-hydroxy steroid dehydrogenase type II (HSD2) play a role in aldosterone stimulation of salt intake. Adult WKY rats received microinjections of a short hairpin RNA for the MR or a scrambled RNA into the NTS and aldosterone-filled osmotic mini-pumps were implanted subcutaneously and connected to tubing within the 4th ventricle to infuse aldosterone at a rate of 25ng/h. Aldosterone infusion stimulated salt intake and MR knock down successfully reduced the aldosterone stimulated salt intake. Post-mortem immunohistochemistry revealed a significant reduction in the number of NTS neurons exhibiting immunoreactivity for the MR Spontaneously hypertensive rats have a greater salt intake than WKY, therefore another study determined the correlation between the activity of HSD2 neurons, indicated by expression of c-fos and FosB, and increased salt intake in SHR. Very little evidence for co-localization of HSD2 and c-fos or FosB was found using immunohistochemistry and Western blotting. The results indicate that HSD2 neurons in NTS can mediate the increased salt intake induced by aldosterone in the 4th ventricle. Increased activation of HSD2 neurons does not appear to account for the elevated salt intake observed in SHR.