Role of renal afferent nerve in the regulation of blood pressure

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The kidney plays an important role in the regulation of systemic blood pressure via the metabolism of water and sodium, and via humoral factors such as the renin-angiotensin system. However, there is little information about the role of the renal afferent nerve. The present study was designed to clarify the role of the renal afferent nerve in the regulation of blood pressure, using Wistar-Kyoto rats (WKY) and spontaneously hypertensive rat (SHR).[Methods] Thirteen to 15-week-old WKY and SHR were used in this investigation. Under pentobarbital anesthesia, the left renal sympathetic nerves were exposed through a midline abdominal incision. Rectangular pulses were delivered to the renal nerve. The frequency was varied between 1 and 20 Hz, while the voltage and duration of stimulation were held constant (10 V and 1 msec, respectively). For recording of renal afferent nerve activity, the renal nerve was sectioned, the peripheral end of the sectioned nerve placed on electrodes, and the actio … More n potential recorded.[Results and Discussion] 1. Effects of renal afferent nerve stimulation on blood pressure: Renal afferent nerve stimulation at variable frequencies for 20 sec produced a fall in blood pressure in both WKY and SHR in a frequency-dependent fashion. At high frequencies (5-20 Hz) the depressor responses were not different between WKY and SHR, but at low frequencies (1-2 Hz) the responses were significantly smaller in SHR than in WKY. These depressor responses were completely abolished after spinal cord section at C4 or T8, but not after section at L2. It can be concluded that the reflex may be centrally reset in SHR. Thus, the renal afferent cell bodies may be located in the T9-L2 ganglion.2. Recording of renal afferent nerve activity: Since resting afferent nerve discharge is very low, it was difficult to distinguish from noise. However, nerve discharge was significantly increased during partial occlusion of the renal vein. An increase in ureteral pressure did not affect nerve discharge. These results indicate that the renal mechanoreceptor was not stimulated by these changes in renal tissue pressure, so the mechanoreceptor might be located in the intrarenal venous system. Elevation of renal venous pressure increased discharge to similar extent in both WKY and SHR. Less