Evidence for α2-Adrenoceptor Agonist Activity of Minoxidil

Abstract

Abstract The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations. Minoxidil (4.7 × 10−6 m to 4.7 × 10−4 m) produced a concentration-dependent inhibition of field stimulation-evoked responses in rat anococcygeus muscle and vas deferens. The inhibition produced by minoxidil was antagonized by yohimbine (2.5 × 10−7 m). Minoxidil (1.4 × 10−5 m to 4.7 × 10−4 m) also produced a concentration-dependent relaxation in oestrogen-primed potassium chloride-depolarized rat uterus. These responses were blocked not only by yohimbine but also by glibenclamide (202 × 10−8 m). Our results suggest that minoxidil possesses α2-adrenoceptor agonist activity in addition to potassium-channel-opening activity.