The quantal components of the mammalian end‐plate potential

The occurrence of spontaneous subthreshold activity at the neuromuscular junction of the albino rat has been described in a previous paper (Liley, 1956). In the present paper a further study is made of this phenomenon, particularly of the relationship between the spontaneous miniature potentials and the end-plate potential (e.p.p.) involved in normal neuromuscular transmission in the mammal. Recently Boyd & Martin (1955) have demonstrated the quantal nature of the e.p.p. in the cat tenuissimus muscle. In the present paper evidence is produced to show that the e.p.p. in the rat is also composed of summated miniature potentials and in the light of this finding a further investigation has been made into the phenomenon of facilitation at the mammalian neuromuscular junction (Hutter, 1952; Liley & North, 1953; Lundberg & Quilisch, 1953a, b). METHODS