[Responses of toad spinal ganglion neurons in vitro to peripheral repetitive stimulation]

Responses of toad ganglion neurons in vitro to repetitive stimulation of their peripheral processes (sciatic nerve) were intracellularly recorded. The conduction velocity, threshold and resting membrane potential of the 66 recorded neurons ranged 5.3-20.0 m/s, 0.02-0.10 mA, and -50-(-)80 mV, respectively. As the stimulation frequency increased, jitter or delay in onset latency, reduction in amplitude, prolongation in duration, and decrease in afterhyperpolarization occurred in evoked responses of the spinal ganglion neurons. The responses decomposed into three subwaves of S, NM, and M and then missed. The ability of these three components to follow stimulation frequency was in the order of S less than NM less than M; the frequency range during which the spike potential or wave S misses was from 16.7 Hz to 250 Hz. These results indicate that there are three distinct zones in excitability in type A toad spinal ganglion neurons, and some of them may exhibit synaptic or junctional activity.