Chapter 34: Atrial natriuretic factor in the subfornical organ and the organum vasculosum laminae terminalis

Abstract

The atrial natriuretic factor (ANF) has been identified as a hormone that is involved in the regulation of water and electrolyte homeostasis and blood pressure. In the brain ANF acts as a neurotransmitter, it is capable of modulating the membrane excitability of neurons. Circumventricular organs, like the subfornical organ (SFO) and the organum vasculosum laminae terminalis (OVLT) are known to participate in the central control of the salt and water balance. The SFO is outside the blood–brain barrier; it may serve as an open gate for the circulating angiotensin II and ANF. A comparison of alterations in ANF levels in the plasma and the SFO clearly shows that changes in the body fluid and electrolyte homeostasis, both in acute and chronic conditions, or in blood pressure resulted in parallel alterations in ANF levels in the plasma and in the SFO. Circulating angiotensin II influences the neuronal activity in the SFO that can be inhibited by ANF. It has been reported that ANF injected into the SFO blocks angiotensin II-induced drinking.