Background and Aims: Motilin and erythromycin are prokinetic agents that act on the same receptor in gastrointestinal smooth muscle to cause contraction. Both agonists may also cause an increase in outward current. The aim of this study was to determine whether motilin and erythromycin activate calcium-activated potassium (K(Ca)) channels. Methods: Freshly dispersed longitudinal smooth muscle cells of the rabbit colon were used to measure whole-cell outward current and single-channel activity using patch clamp recording methods. Results: Erythromycin and motilin increased a calcium- dependent outward potassium current and increased the open probability of K(Ca) channels of cell-attached patches. Conclusions: Erythromycin and motilin activate K(Ca) channels via an intracellular second messenger system. This effect may modulate the increase in contractility caused by these agonists.
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