CROMAKALIM DILATES RAT CEREBRAL-ARTERIES INVITRO

Using an in vitro perfusion method, we examined the effects of cromakalim, a potassium channel opener, on the superior cerebellar arteries of 24 rats. Cromakalim had no effect on contractions induced by 129 mM K+ until a concentration of 10(-5) M was reached. Contractions evoked by 10(-5) M serotonin were attenuated by cromakalim in a concentration-dependent manner (P < 0.05). The diameter of untreated superior cerebellar arteries remained almost constant with increasing perfusion pressure. However, in the presence of cromakalim, vessel diameter increased with increasing perfusion pressure. At concentrations of 3 x 10(-6) M, cromakalim also inhibited basal myogenic tone and dilated unstimulated arteries (P < 0.01). These results suggest that cromakalim is a cerebrovascular dilator acting on both receptor-mediated and myogenic contractions.