The effect of rANP on the efferent activity of the autonomic nerves

It is well known that the Atrial Natriuretic Peptide (ANP) plays a major role in vasorelaxation and in lowering systolic blood pressure. However, little information is available concerning its effect on the autonomic outflows. The present study deals with the effect of rat ANP (rANP) on the efferent activity of the sympathetic and vagal outflows. Under anesthesia (urethane 700 mg/kg and chrolarose 50 mg/kg, intraperitoneal), the effect of intravenous administration of rANP was observed in rats. A suppression of the efferent activity was recognized after administration of rANP in adrenal, renal and splenic sympathetic nerve fibers, and also in vagal gastric, pancreatic and hepatic nerve fibers. The smallest effective dose was 100 pg. In decerebrated preparations no change in efferent activity after administration of rANP was recognizable. The results indicate that rANP released from the atrium to systemic circulation modulates autonomic outflows through the hypothalamic neurons surrounded by an insufficient blood brain barrier.