POTASSIUM CHANNELS FROM NORMAL AND DENERVATED MOUSE SKELETAL-MUSCLE FIBERS

The properties of singles K+ channels in normal and denervated muscles were compared using the ''patch-clamp'' technique. Single channels we re recorded from vesicles obtained by stretching bundles of normal and denervated extensor digitorium longus (EDL) muscles. The most frequen tly observed channel in normal muscles was a high conductance (266 pS) Ca++ activated K+ channel. Although channel density, as estimated by patch recording, showed a significant decrease in denervated muscles, no differences were found in conductance and gating properties. Anothe r voltage-dependent K+ channel (81 pS) was only recorded from normal m uscles, but never from denervated ones. In addition, a 35 pS conductan ce was recorded from both normal and denervated fibers. This channel d isplayed neither voltage dependence nor sensitivity to tetraethylammon ium (TEA). In contrast, another TEA-insensitive (16 pS) channel was re corded only from denervated muscles. We conclude that denervation indu ces significant changes in the distribution and expression of K+ chann els in mammalian skeletal muscles.