Sodium movements in denervated muscle and the effects of antimycin A.

1. Fibre sodium in rat diaphragm exchanged at a faster rate in muscles which had been denervated 8 days previously. The half-time was 3.7 min for outward movement in denervated muscles and 5.1 min in controls.2. The inward movement of sodium was also faster in denervated muscle as compared with controls, and the calculated permeability to sodium was approximately doubled.3. In the presence of antimycin A (1.8 x 10(-5)M), the outward movement of sodium in denervated diaphragm was slowed and the fibres gained sodium and lost potassium.4. Antimycin markedly reduced the twitch produced by stimulation of denervated diaphragm, and also the response to acetylcholine. Similar effects were found in denervated tibialis anterior of the cat.