Effect of acute footshock stress on the responsiveness of the isolated rat tail artery to phenylephrine and epinephrine.

The effects of acute footshock stress on the sensitivity of the isolated rat tail artery were studied. Footshock stress applied to male Wistar rats (200-300 g) causes subsensitivity to the vasoconstrictor effects of phenylephrine and epinephrine. No significant changes in the pA2 values of prazosin were detected, using epinephrine as the agonist. Footshock stress-induced subsensitivity to epinephrine was not affected by the calcium entry blocker nifedipine. However, nifedipine significantly depressed the maximum response to epinephrine in tail arteries isolated from acute footshock-stressed rats. The present results suggest that acute footshock stress-induced reduced sensitivity to phenylephrine and epinephrine may not be only related to events at the alpha-adrenoceptor level. The nifedipine-induced depression of the maximum response to epinephrine suggests a role for the calcium mobilization processes in the vascular responsiveness during acute stress.