Abstract
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.
Footnotes
- Accepted January 17, 1966.
- The Williams & Wilkins Comapny
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