Determination of conduction velocities of single myelinated and unmyelinated axons using a method of spike-triggered averaging

This report describes a modification of the microfilament recording technique for neurophysiological studies of peripheral nerve. The conduction velocity (CV) of a single unit can be directly observed by recording the same action potential (AP) at two sites along the nerve. A single axon AP is obtained from the whole nerve trunk by computer averaging triggered on the occurrence of the microfilament AP. After acute proximal section, recordings were made in the saphenous nerves of 46 adult male Sprague-Dawley rats (18 of which had undergone unilateral saphenous neurotomy 6 to 28 days previously). A total of 169 fibers representing a wide range of CVs (0.8-100 m/s) were recorded. The CVs of myelinated and unmyelinated peripheral axons were consistently obtained with this method. This technique is applicable in axons manifesting spontaneous activity or after activation by mechanical or pharmacological stimuli.