Influence of Intracerebroventricularly-administered Ouabain on Renal Nerve Activity in Rabbits

Lim, Young Cahi

Abstract

Central nervous system is involved with the regulation of renal function either through nerual mechanisms or humoral mechanisms. Intracerebroventricularly-administred (icv) ouabain has been shown to elicits antidiuresis and antinatriuresis in rabbits. Also through denervation experiment, renal nerves have been presented to be responsible for this renal action of central ouabain. However, the quantitative and time-dependent changes of renal nerve activity (RNA) has not yet been clarified in the role of renal nerves which are closely involved with the renal action of central ouabain. This study was therefore undertaken in order to observe the influence of icv ouabain on the regulation of RNA in rabbits. Icv ouabain 10microgram/kg, a dose which produced the most pronounced antidiuresis and antonatriuresis, elicited the increase of RNA right after drug administration. RNA at 5 min increased up to 168% of the control and RNA at 10 min 202% of the control. The maximal RNA (270% of the control) was observed at about 15 min after drug administration, in which period the most remarkable antidiuresis and antinatriuresis is produced by icv ouabain, and such increased RNA still persisted thereafter. Central ouabain-induced RNA increase was accompanied by increase in systemic blood pressure and decrease in heart rate. Blood pressure (BP) began to increase right after administration and showed maximal increase at about 10 to 20 min period. Thereafter BP tended to recover but it was still above control BP. Heart rate decreased right after administration and maximal decrease was observed at 5 min. Thereafter heart rate showed recovery to the control. During the first 20-min period after drug administration, the proportional relationship was observed mutually between renal nerve activity changes and antidiuretic or antinatriuretic amounts. These observations suggest that central ouabain increase RNA, through which renal excretory function might be reduced.