Atrial Natriuretic Factor: Neuromodulator of the Central Nervous System Regulation of Blood Pressure

Extensive examination in the mammalian brain for the presence of atrial natriuretic factors (ANF) has revealed both peptide and receptors specifically distributed throughout the central nervous system. High concentrations of ANF have been found in several hypothalamic nuclei, septal areas, the anteroventral third ventricular area (AV3V), and the median eminence, whereas moderate concentrations have been detected in the circumventricular organs and several brainstem nuclei. The receptors for ANF have been found in moderate to high concentrations in the olfactory lobe, AV3V region, and several circumventricular organs (subfornical organ, organum vasculosum of the lamina terminalis) as well as the nucleus tractus solitarius, median eminence, and choroid plexus. These findings suggest a role for ANF in modulating fluid and electrolyte balance, and blood pressure in this compartment, analogous to the proposed actions of this peptide hormone in the periphery. To determine whether ANF might function as a neuromodulator of blood pressure, we administered ANF via fourth ventricular injection into the brain of hypertensive (SHR) and normotensive rats (WKY). Atrial natriuretic factor caused a moderate and significant decrease in mean arterial blood pressure in both strains. The action of ANF appeared to be mediated by activating the central alpha 2-adrenergic nervous system, probably through the release of catecholamines. Further, a dependence on the secretion and action of an endogenous opioid was probably involved; heart rate was unaffected in these studies. Experiments from other laboratories indicate that central ANF may modulate the pressor effects of centrally acting angiotensin II.(ABSTRACT TRUNCATED AT 250 WORDS)