Effects of Alpha Adrenoceptor Blockade on Renal Nerve Stimulation-Induced Norepinephrine Release and Vasoconstriction in the Dog Kidney1

Effects of alpha-antagonists on renal norepinephnne(NE) release and vasoconstriction induced by renal nerve stimulation (RNS) were examined in pentobarbital-anesthetized dogs. RNS at 1,2 and 3 Hz (1 msec duration, 1 0-20 V) for 1 mm decreased renal blood flow (RBF) and increased both the renal venous NE concentration (NEC) and calculated renal NE efflux (NEE). The RBF responses to 2 and 3 Hz RNS and NEC responses to 1, 2 and 3 Hz RNS during intrarenal arterial infusion of yohimbine (1.0 g/kg/min) were greater than those observed dunng the control period. The NEE responses to 1 and 2 Hz RNS, but not to 3 Hz RNS, were also potentiated by the yohimbine infusion. Prazosin treatment (0.2 mg/kg i.v.) attenuated the RBF responses. Sub-sequent infusion of yohimbine potentiated both the NEC and NEE responses to 1, 2 and 3 Hz RNS in this alpha-i adrenocep