BARIUM RESISTANT POTASSIUM CURRENT IN MAMMALIAN SKELETAL-MUSCLE FOLLOWING DENERVATION

Inward rectifier potassium channels are thought to be related to resti ng membrane potential and in innervated skeletal muscle they are speci ally sensitive to the blocking action of Ba2+ ions. After denervation other channels are known to become resistant to their blockers. We stu dy the effect of Ba2+ upon the inward rectifier potassium channels aft er denervation. Rat extensor digitorum longus fibers were equilibrated for 150 minutes in 150 mM KCl; when they were returned to 5 mM KCl th e resting potential went back to its original level with a half time o f 35 minutes. This repolarization was blocked by 5 mM BaCl2 in innerva ted muscles and in muscles denervated for 7 days, but failed to do so after 14 days of denervation. Voltage-clamp experiments performed in l umbricalis denervated muscle showed a lack of effect of Ba2+ upon pota ssium current after 18 days of denervation. This results suggest that the inward rectifier potassium channels become resistant to Ba2+ ions after denervation, indicating a neural influence.