| 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. |
