Acetylcholine depolarization of the dorsal root nerve terminals in the amphibian spinal cord

When ACh or carbachol was directly applied to the isolated amphibian spinal cord, a slow depolarization which originated at or near the dorsal root nerve terminals could be recorded by means of the sucrose-gap method. This depolarization was a transient phenomenon. A marked and transient decrease in the amplitude of the DR-DRP was observed during the development of the ACh depolarization. With relatively small concentrations of ACh, the reduced amplitude of the DR-DRP was gradually restored to an almost normal value within 30–40 min. The depolarization of the dorsal root nerve terminals as well as the reduction in the size of the DR-DRP, caused by ACh or carbachol, were enhanced by anti-AChE's and prevented by atropine, DHE, d-TC or nicotine. These pharmacological properties were similar to those of the VR-DRP. On the basis of the experimental observations, the possible location of the cholinoceptive receptor sites in the amphibian spinal cord was discussed.