Competitive antagonism by glibenclamide of cromakalim inhibition of twitch contractions in rabbit vas deferens

Electrically induced contractions of the rabbit isolated vas deferens were potentiated by carbachol but inhibited by the K+ channel opener cromakalim. The inhibition by cromakalim could be competitively antagonized by 10(-7)-10(-6) M glibenclamide (pA2 = 7.17) and was also reversed by carbachol, extra K+ or Bay k 8644. The data support the view that smooth muscle membrane depolarization is the cause for carbachol potentiation in rabbit vas deferens and that hyperpolarization by cromakalim is susceptible to blockade by the inhibitor of ATP-sensitive K+ channels, glibenclamide.