title: Evaluation of presynaptic alpha-receptor function in the canine renal vascular bed.
abstract: The functional significance of presynaptic alpha-receptor modulation of sympathetic nerves was examined in vivo in the canine renal vascular bed. In pentobarbital-anesthetized dogs, the vasoconstrictor response to renal nerve stimulation and exogenous norepinephrine was compared before and during intra-arterial infusions of epinephrine, oxymetazoline, clonidine, and norepinephrine. Only epinephrine produced a modest decrease in stimulation-induced vasoconstriction at 1 Hz. After pretreatment with desipramine, intra-arterial infusions of epinephrine or norepinephrine did not alter stimulation-induced vasoconstrictor responses relative to exogenous norepinephrine. Further, neither yohimbine nor phentolamine (10(-9) to 10(-3) g, intra-arterial) produced a distinctly increased vasoconstrictor response to nerve stimulation relative to exogenous norepinephrine. Thus, studies using alpha-receptor agonists, antagonists, and inhibition of neuronal uptake failed to reveal a physiologically significant alpha-receptor-mediated negative feedback mechanism for stimulation-induced vasoconstriction in the canine renal vascular bed.
mesh_terms: D000818:Animals; D002417:Cattle; D003000:Clonidine / Q000494:pharmacology; D003891:Desipramine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004336:Drug Antagonism; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D007668:Kidney / Q000098:blood supply*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014666:Vasomotor System / Q000187:drug effects*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D015016:Yohimbine; D003000:Clonidine; D003891:Desipramine; D009638:Norepinephrine; D004837:Epinephrine; D010646:Phentolamine