Further evidence that a beta-adrenergic mechanism regulates water intake: role of the subfornical organ.

The daily water intake was reduced in rats by subcutaneous administration of propranolol. The fluid intake after 24 h of dehydration in nephrectomized animals was decreased by propranolol. In intact rats diazepam did not modify the postdehydration water intake. Propranolol injected into subfornical organ decreased water consumption after 24 h of fluid deprivation but did not change the dipsogenic response to carbachol given in the same structure. These results suggest that a beta-adrenoceptor mechanism participates in the regulation of the daily water intake. After a stimulus such as dehydration, beta-blockade modifies water consumption by a non-renal mechanism. This mechanism involves neither a general depressant nervous activity nor a local anesthetic action and could be located in a periventricular structure, the subfornical organ.