抄録
1. Facilitation of nerve muscle transmission by repetitive stimulation was usually observed in frog preparation with wide range of stimuli frequencies, while occasionally observed in rat and rabbit muscle in situ only at certain range of frequencies. The facilitation of frog muscle was made more remarkable by reducing Ca concentration in the medium, and was made less remarkable by post-tetanic potentiation and Ca increase in the medium.
2. Double shock experiment on frog preparation showed two distinguished kinds and an intermediate of the spike height-interval curve. One curve should be transfered to another by changing the Ca concentration in bathing medium.
3. Double shock experiment on single nerve fibre-single muscle fibre preparation showed that there were two modes of transmission; in one, the impulse was transmitted by the first as well as the second shock, but the second shock occasionally failed in some definite shock interval. In the other, the impulse was transmitted only by the second shock, and that only in some limited phase of shock intervals. And the one could be transfered to the other by changing the Ca concentration.
4. The various spike-interval relation observed in the whole muscle could be explained by considering the relative composition of these two kinds of synapses.
5. The time course of the size of the second e. p.p. did not show two kinds, but the difference of whether it attains the firing level or not would give rise to two kinds of synapse.
6. Repetitive stimulation was carried out also on the frog end-plate potential, small nerve junctional potential and the fish muscle, showing facilitation in a certain range of frequencies.
This research was supported in part by a research grant from the Educational Ministry.
