SUPERSENSITIVITY IN PERFUSED ISOLATED ARTERIES AFTER RESERPINE

¹ Department of Pharmacology, University of Mississippi Medical Center, Jackson, Mississippi

An isolated small artery preparation was used to investigate supersensitivity following reserpine pretreatment of dogs. Perfusion and single dose injections of norepinephrine were used to evoke vasoconstrictor responses. Supersensitivity was demonstrated in vessels removed from animals given 0.4 mg/kg reserpine (Serpasil) 24 and 48 hours prior to the experiments. Significance of the increased sensitivity of the reserpinized vessels could only be shown in the injection experiments.

Tyramine and ephedrine in the perfusion experiments were shown to act in accordance with current concepts. Tyramine and ephedrine both caused a constrictor response in control vessels, while in reserpinized vessels no significant responses were obtained. In the injection experiments, no conclusive results could be obtained at the dose levels employed for the two amines (tyramine at 10^-4 g and ephedrine at 10^-3 g).

Time constants for a single response indicated that reserpinized vessels initially responded to norepinephrine more rapidly than controls. The total time required by the reserpinized vessels to reach maximum response was greater than for the control vessels. This was explained on the basis of a much slower flow at the time of maximum response.

It was suggested that the results could be explained by assuming that reserpine increases the effective receptor areas on the effector organ (muscle) either functionally or anatomically.