Arteriolar tone is determined by activity of ATP-sensitive potassium channels

ATP-sensitive potassium channels (KATP) in determining rest-ing arteriolar tone and vasodilator reactivity was assessed in superfused, hamster microcirculatory beds studied via intravital microscopy. Under resting conditions, the selective KATP blocker, glibenclamide, produced concentration-dependent va-soconstriction in both the cheek pouch and the cremaster muscle. Concentration-related constriction of cheek pouch ar-terioles was also observed with tetrapentylammonium, although this agent appeared to have toxic effects on the microcircula-tion. Glibenclamide (2 PM) abolished arteriolar vasodilation to cromakalim and pinacidil over a concentration range (10 nM-1 PM) in which these agents are selective KATP agonists and also significantly inhibited adenosine-, carbacyclin-, and isoproter-enol-induced vasodilation. In contrast, responses to other vaso-dilators were not significantly affected [methacholine, forskolin