抄録
The effects of K channel blockers on slow waves and pacemaker potentials recorded from mouse small intestine were investigated intracellulary. Application of iberiotoxin, a blocker of large conductance Ca-activated K channel, or charybdotoxin, a blocker of intermediate conductance Ca-activated K channel, had no effect on the generation of slow waves recorded from circular smooth muscles, while the blocking of small conductance Ca-activated K channel (SK channel) by apamin depolarized the membrane and inhibited the early, rapid repolarization of slow waves. 4-Aminopyridine (4-AP), a blocker of transient outward K channel, depolarized the membrane and increased the amplitude and maximum rate of rise (dV/dtmax) of the primary component of slow waves. On the other hand, the amplitude and dV/dtmax of pacemaker potentials recorded from in situ interstitial cells of Cajal distributed in the myenteric region (ICC-MY) were decreased by application of apamin or 4-AP. These observations indicate that both apamin-sensitive K conductance and 4-AP-sensitive K conductance may contribute to the resting membrane potential of circular smooth muscles. The observations also indicate that 4-AP-sensitive K conductance is likely to be activated during the generation of the primary component of slow waves. The early, rapid repolarization seems to be a specific response of smooth muscle cells resulting from the activation of apamin-sensitive K conductance. [J Physiol Sci. 2008;58 Suppl:S55]
