Abstract
The effects of the immersion of nerve-muscle preparations of frog in Ringer solution on the excitation and contraction phenomena were followed up to 24 hours.
1. The twitch responses of the muscle to indirect and direct electrical stimulations decreased to quite similar degree until 8 hours after immersion. However, it was observed that the twitch responses to indirect stimulations reduced more prominently after 8 hours.
2. Until at least 8 hours after immersion, no changes in action potentials of the whole muscles elicited by indirect stimulations were observed.
3. Not only the action potentials of the nerve trunks, but also the resting and action potentials of the directly stimulated muscle fibres were quite similar to those in the control even at 24 hours after immersion.
4. There were no differences in size and shape of the caffeine-induced contractures between the muscle immersed in Ringer solution for 24 hours and the control.
5. In the muscle surviving for 24 hours in Ringer solution, the threshold concentration of Ach to produce contractures was about 10 times higher than that in the control.
6. It is concluded that the failure of the E-C coupling processes in the surviving nerve-muscle preparations starts in earlier stage prior to functional disturbances of the end-plate, and remains incomplete even after 24 hours when the end-plate transmission fails completely.
