It has been well known that the e. p. p. of the frog muscle shows facilitation or depression according to the state of muscles. Concerning the transmitter output the quantal nature and its relation to repetition of impulses have been reported by del Castillo and Katz and the dependence of neuro-muscular facilitation and depression on Ca++ content of the medium by Lundberg and Quillish and other authors. The purpose of the present paper is to get further information about the pattern of e. p. p. trains in connection with the transmitter output. The intra- or extracellular electrode was adopted for recording the train of e. p. p. The pattern of e. p. p. and its change evoked by the train of nerve impulses of various frequencies were investigated in various media, in the post-tetanic potentiation or in the stretched state of muscles. Ca++ deficiency or Mg++ addition brought about facilitation, and excess of Ca++ depression; post-tetanic potentiation, stretching of muscles had the similar effect as the latter. Whereas vagostigmine 10-6 did not produce any change of the pattern of curarized muscles at least concerning its pattern. Therefore the change of pattern in this experiment came probably from the change of transmitter output, of which decrease resulted in facilitation; increase in depression, and did not come from the change of post-synaptic sensitivity to Ach.
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Wakabayashi et al. (1964) studied this question.