The periventricular anteroventral third ventricle (AV3V): Its relationship with the subfornical organ and neural systems involved in maintaining body fluid homeostasis

The periventricular tissue surrounding the anteroventral third ventricle (AV3V) is critically involved in the maintenance of normal body fluid balance and distribution. The present review examines the anatomical, neurochemical, and functional relationship of the AV3V with neural systems subserving body fluid homeostasis. In particular, the nature of AV3V afferents from the subfornical organ (SFO) and from brainstem noradrenergic cell groups is discussed. A model is presented proposing that specific structures within the AV3V, particularly along the ventral lamina terminalis, function to integrate information derived from blood-borne angiotensin II (via the SFO) with input arising from vascular pressure/volume receptors. The resultant of this integration is important for the generation of a normal component of thirst (i.e., drinking) associated with extracellular dehydration.