The interaction between renin-angiotensin and sympathetic systems in the renal vasculature of Wistar-Kyoto rats

The various interactions between the renin-angiotensin system and the sympathetic system have been established at different levels and have been shown to bear prominent pathophysiological implications. This study was undertaken to characterize the renal responses to acute unilateral renal denervation of the left kidney in anaesthetized Wistar-Kyoto rats (WKY) by examining the effect of acute unilateral renal denervation on the renal hemodynamic responses to renal nerve stimulation (RNS). Twenty-four male WKY rats underwent acute unilateral renal denervation. After 7 days treatment with losartan, the overnight fasted rats were anesthetized (sodium pentobarbitone, 60 mg/kg i.p.) and renal vasoconstrictor experiments were done. The renal nerves were directly stimulated at a sequence of frequencies of 1, 2, 4, 6, 8, and 10 Hz at 0.2 ms duration and 15V for a period of 15 seconds in ascending and descending manner. The changes in the renal vasoconstrictor responses were determined in terms of reductions in renal blood flow caused by renal nerve stimulation. The data showed that there was significantly (all P<0.05) decreased renal vascular responsiveness to neural stimuli in denervated rats compared to those with intact renal nerves. In losartan treated denervated WKY rats, there were significant (all P<0.05) reductions in the renal vasoconstrictor responses to neural stimuli as compared to that of untreated denervated WKY rats. These data also suggested a possible interaction between sympathetic nervous system (SNS) and renin-angiotensin system (RAS) in terms of a crosstalk relationship between renal AT₁ and α₁ -adrenoceptor subtypes in the renal vasculature of normal rats.