title: Specific alpha-adrenergic receptor desensitization in vascular smooth muscle.
abstract: Specific desensitization of vascular tissue to norepinephrine was studied using an open-ring-type strip preparation of rabbit aorta. Aortae were taken from untreated, reserpine-pretreated (0.1 mg/kg/day; 3, 5, or 7 days) and 6-hydroxydropamine-pretreated (50 mg/kg; 3 or 7 days before sacrifice) rabbits. Aortic strips from the pretreated rabbits were supersensitive to norepinephrine. Subsequent to obtaining the first dose-response curve for norepinephrine, aortic strips were less sensitive to norepinephrine. It was found that desensitization to norepinephrine occurred following 10 min preincubation with 10(-6)m norepinephrine, and 20 min preincubation with 10(-7)m norepinephrine. The desensitization of supersensitive strips was significantly greater than in controls. Dopamine and isoproterenol desensitized both untreated and pretreated strips to norepinephrine. Phenylephrine desensitized strips to norepinephrine from 6-hydroxydopamine-pretreated rabbits. Acetylcholine and potassium did not desensitize strips to norepinephrine; however, acetylcholine desensitized strips to acetylcholine. It is concluded from these studies that norepinephrine desensitization in a specific alpha-adrenergic-related event.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000294:innervation; D001158:Arteries / Q000187:drug effects*; D004298:Dopamine / Q000494:pharmacology; D005260:Female; D006892:Hydroxydopamines / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects* / Q000294:innervation; D009638:Norepinephrine / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D011941:Receptors, Adrenergic / Q000187:drug effects*; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012110:Reserpine / Q000494:pharmacology; D013566:Sympathomimetics / Q000494:pharmacology*
chemical_list: D006892:Hydroxydopamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D013566:Sympathomimetics; D010656:Phenylephrine; D012110:Reserpine; D007545:Isoproterenol; D000109:Acetylcholine; D011188:Potassium; D004298:Dopamine; D009638:Norepinephrine