Inhibition of KATP channels in the rat tail artery by neurally released noradrenaline acting on postjunctional α2-adrenoceptors

Abstract

In rat tail artery, activation of postjunctional α2 -adrenoceptors by noradrenaline (NA) released from sympathetic axons produces a slow depolarization (NAD) of the smooth muscle through a decrease in K+ conductance. In this study we used intracellular recording to investigate whether the K+ channel involved is the ATP-sensitive K+ (KATP) channel. Changes in membrane resistance were monitored by measuring the time constant of decay of excitatory junction potentials. The KATP channel blockers, glibenclamide (10 μM) and PNU 37883A (5 μM), depolarized the smooth muscle and increased membrane resistance. Conversely, the KATP channel openers, pinacidil (0.1 and 0.5 μM) and levcromakalim (0.1 μM),..