Effects of 6-Hydroxydopamine Pretreatment on in vivo Femoral Arterial Responses to Vasodilator Agents

Abstract

Reserpine has been previously shown to generally enhance femoral arterial vasodilator responses as indicated by increased slopes of regression lines relating decreases in resistance produced by injections of vasodilator agents to resistance prior to the injections. We have examined the same parameters in dogs pretreated with 6-hydroxydopamine. In contrast, 6-hydroxydopamine either decreased (nitroglycerin, adenosine) or had no effect (isoproterenol, acetylcholine) on femoral arterial vasodilator responses. In a second set of animals, reserpine was administered after pretreatment with 6-hydroxydopamine, and reserpine again tended to augment responses to vasodilator agents. These data suggest that reserpine’s effects on vasodilator responses may be a direct effect on vascular smooth muscle and was not dependent on its effects on sympathetic innervation of the femoral bed. The decreased vasodilator responses to certain agents induced by 6-hydroxydopamine, in contrast, may have been attributable to loss of a presynaptic component of their mechanism(s) of vasodilator action.

Effect of Reserpine on Relaxant Responses of Canine Femoral Arterial Strips

“…These conflicting reports from in vitro studies concerning the effect of reserpine on responses to vasodilator agents led us to study the problem in vivo. We found that reserpine pretreatment generally enhanced the in vivo vasodilator responses of the femoral arterial bed of the dog to acetylcholine, adenosine, dibutyryl cyclic AMP, hydralazine, isoprenaline, and glyceryl trinitrate (Cauvin, Devia & Kirkendol, 1981). The question arose whether increased in vivo vasodilator responses induced by reserpine were due to its effects on the sympathetic nervous system.…”