Mechanical degeneration of denervated amphibian gastrocnemius muscle

The authors studied the amplitude of contraction and force-velocity capabilities of isolated whole denervated gastrocnemius muscles. One gastrocnemius from each frog in a population was denervated by resection of the sciatic nerve, leaving the sciatic nerve of the contralateral gastrocnemius exposed but intact. At fixed postoperative time periods, a frog was sacrificed and both gastrocnemii were dissected, allowing the sciatic nerves to remain attached to the muscles. Amplitudes of twitch contractions in both muscles were observed for contractions against loads of 10, 20, 30, and 40 N, and maximum velocities of contraction were also for tetanizing stimuli with the same loads. Twitch amplitudes of the denervated muscles, when normalized by the measurements from the unoperated contralateral muscles, were found to increase over the first three postoperative days and then to decay for several days. In contrast, no strong effect on maximum velocity of contraction was observed.