An outwardly rectifying and deactivating chloride channel expressed by interstitial cells of cajal from the murine small intestine

Recent studies have suggested a role for a chloride current in the modulation of pacemaker potentials generated by interstitial cells of Cajal. Patch-clamp recordings were made from inside-out patches of cultured interstitial cells of Cajal from the murine small intestine. The majority of patches were quiescent immediately after excision, but in some patches currents activated spontaneously after a period of 10 min to 1 h. Currents could also be activated by strongly polarizing the patch. It was found that the currents activated in both cases included a chloride channel. This channel could also be activated by ATP and the catalytic subunit of protein kinase A. The channel had conductance states (+/- SD) of 53 +/- 25.35, 126 +/- 21.44, 180 +/- 12.57 and 211 +/- 8.86 pS. It was outwardly rectifying (as a function of open probability) and deactivated (i.e., gave a tail current) but showed no inactivation. The permeability sequence of the channel was I->> Br->= Cl-> Asp(-). It was unaffected in magnitude or rectification by changing the free Ca2+ concentration of the bath between < 10 nM, 100 nM (control) and 2 mM.