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-hydroxydopamine-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 is a specific α-adrenergic-related event.

Keywords:
Vascular adrenergic receptor, Sympathomimetics, Desensitization, Reserpine, 6-Hydroxydopamine, Supersensitivity
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© 1978 S. Karger AG, Basel
1978
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