Area postrema and adjacent nucleus of the solitary tract in water and sodium balance.

Lesions of the area postrema (AP) and adjacent caudal medial nucleus of the solitary tract (cmNTS) cause significant changes in water and sodium balance. Lesioned rats display a permanent polydipsia, which in part is due to a primary polyuria. Water-to-food ratios are elevated chronically. Lesioned rats are unable to concentrate their urine as well as controls. In addition, lesioned rats overdrink in response to 24-h water deprivation. This lesion also causes a natriuresis and an overconsumption of 3% NaCl solution. These findings establish the AP-cmNTS as an important part of the neurocircuitry underlying water and sodium balance.