Effects of alpha adrenoceptor blockade on renal nerve stimulation-induced norepinephrine release and vasoconstriction in the dog kidney.
Effects of alpha-antagonists on renal norepinephrine (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, 10-20 V) for 1 min 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 micrograms/kg/min) were greater than those observed during 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. Subsequent infusion of yohimbine potentiated both the NEC and NEE responses to 1, 2 and 3 Hz RNS in this alpha-1 adrenoceptor-blocked state. These results suggest that an alpha-2 adrenoceptor-mediated inhibitory mechanism of neural NE release exists in the dog kidney, which can be activated by endogenously released catecholamines to modulate the neural control of renal hemodynamics. Alpha-1 adrenoceptor-mediated renal vasoconstriction may affect the evaluation of neural NE release by NEE when high-frequency RNS is applied during inhibition of the alpha-2 adrenoceptor-mediated mechanism.
Hisa
H
H
Department of Pharmacology, Tohoku University, Sendai, Japan.
Araki
S
S
Tomura
Y
Y
Hayashi
Y
Y
Satoh
S
S
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D007668:Kidney / Q000294:innervation*; D008297:Male; D009638:Norepinephrine / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D012079:Renal Circulation / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D009638:Norepinephrine; D011224:Prazosin