Effect of trimebutine on K+ current in rabbit ileal smooth muscle cells

The effect of trimebutine on the K+ current in rabbit ileal smooth muscle cells was investigated using the whole-cell patch-clamp technique. Trimebutine (10 microM) inhibited an outward current consisting of a Ca(2+)-dependent K+ current (IKCa) and Ca(2+)-independent K+ current (IKv), elicited by stepping from -80 to -20 mV or more positive. Trimebutine reduced dose dependently the IKv amplitude with an IC50 of 7.6 microM and IKCa amplitude with an IC50 of 23.5 microM. The IKv inhibition was neither voltage- nor use-dependent. Trimebutine (1-100 microM) decreased the amplitude and discharge rate of spontaneous transient outward currents. Trimebutine (30 microM) produced a sustained membrane depolarization of about 10 mV accompanied by a decrease in membrane conductance. The results suggest that the excitatory effects of trimebutine on the gastrointestinal tract may be attributable to the inhibitory action on the K+ current.