The Role of the Septal Area in the Regulation of Drinking Behavior and Plasma ADH Secretion

Abstract

Drinking behavior and ADH secretion are normally regulated by two physiological parameters: plasma osmolality and blood volume. A variety of experiments dating back to the classical observations of Verney⁹ indicate that signals elicited by increased plasma osmolality and reduced extracellular fluid volume stimulate the release of ADH and initiate the drinking of water. Single neurons in the septal area respond with an increase in activity to only plasma osmolality increases, but not to extracellular hypovolemia⁵. Thus of the two stimuli which normally elicit thirst and ADH secretion, the septal nuclei of the rat forebrain seem to be involved only in the mechanisms regulating intracellular fluid volume. To investigate this hypothesis water intake and circulating levels of ADH were measured in sham- and septal-lesioned rats receiving a subcutaneous injection of hypertonic saline, which reduces intracellular fluid volume, or polyethylen glycol, which reduces extracellular fluid volume. Additionally, rats received total, lateral or medio-ventral destruction of the septal area in an attempt to delineate the critical region involved in drinking behavior and ADH release.