Abstract
In the preaent paper, the influence of the extension of muscle on the facilitation of end plate was investigated.
When 2 successive nerve impulses were given at an adequate interval to the innervating nerve at the end plate, the end plate potential induced by the second impulse is larger than that induced by a single nerve impulse. In other words, facilitation is observed at the end plate.
The extension of muscle induces a larger end plate potential, though the extension induces a smaller facilitation in grade.
In the present paper, the authors investigated the phenomenon induced when the first impulse was given directly to the muscle and the second impulse was given to the nerve with the extension of the muscle.
In the present experiments, sartorius muscle-nerve rpreparation was employed. The first impulse was given at the aneural portion of the pelvic end of the muscle, and the second impulse was given to the nerve. By this method, the excitability of the end plate, i. e., the recovery curve of the non-curarized muscle was investigated. The absolute refractory period of this complex excitatory system was 7 cosec, and the relative refractory period was roughly 10 mesc, which were roughly coincided with the refractory period of the curarized muscle. When similar experiments were carried out with muscles extended by 20%, supernormal period lasting roughly for 14 msec following relative refractory period lasting roughly for 3.5 msec. The fact means that the number of the excited muscle fibres has increases, thus the facilitation of the end plate occurred.
In other words, since the excitatory pattern in the case when the first impulse was given to the nerve differs from that in the case when 2 successive impulses were given to the nerve, the influence of the extension of muscle on the facilitation of the end plate in each of the above two cases is considered to be contradicting each other.
