A RELATIVELY NONSPECIFIC SUPERSENSITIVITY IN AORTIC STRIPS RESULTING FROM PRETREATMENT WITH RESERPINE

¹ Department of Pharmacology, West Virginia University Medical Center, Morgantown, West Virginia

The effects of several schedules of pretreatment with reserpine on the sensitivity of the isolated aortic strip of the rabbit have been studied. The following treatments were employed: 1 mg/kg/day for 1 day, 3 mg/kg/day for 1 day, 0.3 mg/kg/day for 3 days, 1 mg/kg/day for 3 days, 0.3 mg/kg/day for 7 days and 0.3 mg/kg/day for 14 days. All treatments caused a shift to the right of the dose-response curve of tyramine, indicating subsensitivity. There was no reduction in maximum. The responses to tyramine were only slightly antagonized by phentolamine. All treatments with reserpine caused a shift to the left of the dose-response curve of norepinephrine (supersensitivity). The optimal schedule of treatment with reserpine was determined to be 0.3 mg/kg/day for 3 days. The sensitivity was also increased to acetylcholine and potassium, but not to 5-hydroxytryptamine, histamine or angiotensin. A dose of phentolamine which produced marked antagonism against norepinephrine caused very little antagonism of acetylcholine and none of potassium. Pretreatment of cats with reserpine, 0.1 mg/kg/day for 3 days, produced supersensitivity to norepinephrine in aortic strips from that species also. The nonspecific nature of the supersensitivity is discussed as evidence that the supersensitivity is due to a physiologic change beyond the receptors.

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