Evidence for α2-adrenoceptor agonist activity of minoxidil

Abstract

The present investigation was undertaken to study the mechanism of action of minoxidil using various smooth muscle preparations. Minoxidil (4.7 x 10-6 M to 4.7 x 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 x 10-7 M). Minoxidil (1.4 x 10-5 M to 4.7 x 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 (2.02 x 10-8 M). Our results suggest that minoxidil possesses α2-adrenoceptor agonist activity in addition to potassium channel-opening activity.