Effect of saline loading on ANP in the cerebrospinal fluid of rats

In order to investigate the effect of saline loading on the atrial natriuretic peptide (ANP) in the central nervous system (CNS), time course measurements of the ANP content in the cerebrospinal fluid (CSF), blood pressure, water and electrolyte balances were carried out after saline loading in rats. Cisternal saline loading (120 ml/day) was found to induce a significant increase in urinary volume and electrolyte excretion, and to cause an initial rise in mean arterial blood pressure (MAP) in WKY rats. The ANP content in the CSF was significantly increased after saline loading, as compared to that in the control period. The ANP in both the plasma and CSF revealed a significant increase over the control values following chronic saline loading. Based on these results, it is suggested that the ANP in the CSF could exert a regulatory effect on the blood pressure and water balance, either by a direct action on the kidney or indirectly via an action on the CNS.