On conduction of the action potential wave through the dorsal root ganglion.

Abstract

It has been reported 1 that the action potential wave started by stimulation of the sciatic nerve arrives in the dorsal roots of that nerve somewhat later than in its ventral roots. Further experimentation now makes possible the presentation of additional data bearing on this observation. In fifteen quantitative determinations in the bullfrog with the cathode ray oscillograph, the delay of the quickest sensory behind the motor potential wave ranges, with but one exception (in which, due probably to damage to the ventral root, the value was 0.02°), between 0.09 and 0.18°. Omitting the exception, the average delay is 0.143°. Six determinations in the green frog range between 0.04 and 0.14°, with an average of 0.08°. One determination in the cat showed a delay of 0.08° (temp. 35° C.).

We have been able to show that the delay is not due to differences in the rate of propagation of the action potential wave in sensory and motor fibers, either in the nerve trunk or in its roots. Indeed, the fastest sensory fibers conduct at least as fast as the fastest of the motor fibers. The delay must, therefore, develop in the dorsal root ganglion, but how, or in what division of the part of the neuron within the ganglion, it is at present impossible to say.