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Journal of Experimental Biology 51,107-118 (1969)
Published by Company of Biologists 1969

Miniature Excitatory Junction Potentials in the Somatic Muscle of the Earthworm, Pheretima Communissima, in Sodium Free Solution

Y. ITO ¹, H. KURIYAMA ¹, and N. TASHIRO ¹

¹ Department of Physiology, Faculty of Medicine and Dentistry, Kyushu University Fukuoka, Japan

1. Miniature excitatory junction potentials (m.e.j.p.s) could be recorded from the longitudinal muscle layer of earthworm in sodium-free solution.

2. The amplitude and frequency of the m.e.j.p.s indicated the diffuse innervation and random release of the chemical transmitter from the nerve terminals.

3. Generation of the m.e.j.p.s was prevented by treatment with D-tubocurarine, but not by atropine and picrotoxin.

4. Hyperpolarizations of the membrane by applications of inward current increased the frequency and amplitude of the m.e.j.p.s in sodium-free solution.

5. The reversal potential level for the m.e.j.p.s in sodium-free solution was -;20 mV., and this value was 20 mV. negative to that measured in physiological solution. Low-potassium solution shifted the reversal potential levels in a more negative and high-calcium in a less negative direction.

6. The change of the reversal potential produced by a tenfold change of the external potassium concentration was 24.5 mV., and that by change of the external calcium concentration was 17 mV.