Mechanosensitive potassium channels in rat colon sensory neurons

Single-channel recording techniques were used to characterize mechanosensitive channels in identified (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine methanesulfonate labeled) colon sensory neurons dissociated from adult S1 dorsal root ganglia. Channels were found in 30% (7/23) of patches in a cell-attached configuration and in 43% (48/111) of excised inside-out patches. Channels were highly selective for K+, had a slope conductance of 54 pS in symmetrical solutions, and were blocked by tetraethylammonium, amiloride, and benzamil. Channels were also seen under Ca2+ free conditions. Gadolinium (Gd3+), a known blocker of mechanosensitive ion channels, did not block channel activity. Tetrodotoxin and 4-aminopyridine were also ineffective. The cytoskeletal disrupters colchicine and cytochalasin D reduced the percentage of patches containing mechanosensitive channels. These results indicate that rat colon sensory neurons contain K+-selective mechanosensitive channels that may modulate the membrane excitability induced by colonic distension.