Effects of flunarizine on electrical and mechanical responses of smooth muscle cells in basilar and ear arteries of the rabbit.

The effects of flunarizine on electrical and mechanical responses of smooth muscle tissues of the rabbit basilar and ear arteries to transmural stimulation, high-potassium solution (high-K), 5-hydroxytryptamine and noradrenaline were studied. In the basilar artery, 10(-6) M flunarizine (69 min application) blocked spike potentials generated by outward current stimuli or transmural stimulation without change in the resting-membrane potential or membrane resistance. The spike potentials generated in the ear artery were attenuated by a long exposure (up to 2 h) to a high concentration of flunarizine (10(-6) M). Membrane depolarizations produced by high-K, noradrenaline or 5-hydroxytryptamine were not blocked by flunarizine. Flunarizine inhibited smooth muscle contractions produced by transmural stimuli, high-K, noradrenaline or 5-hydroxytryptamine in both arteries, however the inhibition developed slowly, and the ear artery required a longer period of incubation with flunarizine than the basilar artery. The inhibitory effects of flunarizine on basilar artery were more marked against transmural stimulation or high-K induced contractions than against agonist-induced contractions.