Effects of transient receptor potential channel blockers on pacemaker activity in interstitial cells of Cajal from mouse small intestine

The interstitial cells of Cajal (ICCs) are pacemakers in the gastrointestinal tract and transient receptor potential melastatin type 7 (TRPM7) is a candidate for pacemaker channels. The effect of the 5-lipoxygenase (5-LOX) inhibitors NDGA, AA861, MK886 and zileuton on pacemaking activity of ICCs was examined using the whole cell patch clamp technique. NDGA and AA861 decreased the amplitude of pacemaker potentials in ICC clusters, but the resting membrane potentials displayed little change, respectively. Also, perfusing NDGA and AA861 into the bath reduced both inward current and outward current in TRPM7-like current in single ICC, respectively. But, they had no effects on Ca(2+) activated Cl(-) currents. The 5-LOX inhibitors MK886 and zileuton were, however, ineffective in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC, respectively. A specific TRPC3 inhibitor, pyrazole compound (Pyr3), and a specific TRPM4 inhibitor, 9-phenanthrol, had no effects in pacemaker potentials in ICC clusters and in TRPM7-like current in single ICC. These results suggest that, among the tested 5-LOX inhibitors, NDGA and AA861 modulate the pacemaker activities of the ICCs, and that the TRPM7 channel can affect intestinal motility