Calcium channel blocker-like action of reserpine in smooth muscle

The effect of reserpine on vascular and intestinal smooth muscles was examined. In these muscles, reserpine inhibited the high K(+)-induced contraction, and this inhibitory effect was antagonized by the increase in external Ca2+ concentration and also by a Ca2+ channel activator, Bay k8644. In rabbit aorta, increases in cytosolic Ca2+ level and muscle tension due to high K+ were inhibited in parallel by reserpine. These results suggest that reserpine inhibits L-type Ca2+ channels to inhibit smooth muscle contraction.