Single-channel recording techniques were used to characterize mechanosensit
ive channels in identified (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbo
cyanine methanesulfonate labeled) colon sensory neurons dissociated from ad
ult 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 pa
tches. Channels were highly selective for K+, had a slope conductance of 54
pS in symmetrical solutions, and were blocked by tetraethylammonium, amilo
ride, and benzamil. Channels were also seen under Ca2+ free conditions. Gad
olinium (Gd3+), a known blocker of mechanosensitive ion channels, did not b
lock channel activity. Tetrodotoxin and 4-aminopyridine were also ineffecti
ve. The cytoskeletal disrupters colchicine and cytochalasin D reduced the p
ercentage of patches containing mechanosensitive channels. These results in
dicate that rat colon sensory neurons contain K+-selective mechanosensitive
channels that may modulate the membrane excitability induced by colonic di
stension.