ANTEROVENTRAL WALL OF THE 3RD VENTRICLE AND DORSAL LAMINA-TERMINALIS - HEADQUARTERS FOR CONTROL OF BODY-FLUID HOMEOSTASIS

1. The subfornical organ, median preoptic nucleus and the organum vasc ulosum of the lamina terminalis (OVLT) are a series of structures situ ated in the anterior wall of the third ventricle and form the lamina t erminalis, The OVLT and ventral part of the median preoptic nucleus ar e part of a region known as the anteroventral third ventricle region. 2. Data from many laboratories, using techniques ranging from lesions, electrophysiology, neuropharmacology, Fos expression, immunohistochem istry and receptor localization, indicate that the tissue in the lamin a terminalis plays a major role in many aspects of body fluid and elec trolyte balance. 3. The subfornical organ and OVLT lack the blood-brai n barrier and detect alterations in plasma tonicity and the concentrat ions of circulating hormones such as angiotensin II and possibly atria l natriuretic peptide and relaxin. 4. This information is then integra ted within the lamina terminalis (probably in the median preoptic nucl eus) with neural signals from other brain regions. The neural output f rom the lamina terminalis is distributed to a number of effector sites including the paraventricular (both parvo- and magno-cellular parts) and supraoptic nuclei and influences vasopressin secretion, water drin king, salt intake, renin secretion, renal sodium excretion and cardiov ascular reeulation.