SENSORY NERVE-CONDUCTION VELOCITY OF THE CAUDAL CUTANEOUS SURAL AND MEDIAL CUTANEOUS ANTEBRACHIAL NERVES OF ADULT HORSES

Maximal conduction velocities of compound action potentials evoked by stimuli of 2 times threshold in the caudal cutaneous sural (CCSN) and medial cutaneous antebrachial (MCAN) nerves were determined by averagi ng potentials evoked and recorded through percutaneous needle electrod es. Mean maximal conduction velocities of compound action potentials w ere: CCSN = 61.3 +/- 2.0 meters/second (m/s) and MCAN = 56.4 +/- 2.8 m /s. To confirm accuracy of our percutaneous recordings, compound actio n potentials were recorded through bipolar chlorided silver electrodes from the exposed surfaces of fascicles of the CCSN and the MCAN. The maximal conduction velocities of these potentials were in agreement wi th the conduction velocities of compound action potentials that were e voked and recorded through percutaneous needle electrodes. The specifi city of stimulating and recording sites was verified by recording befo re and after section of the nerves. Stimuli from 3 to 5 times threshol d evoked a second, longer latency, compound action potential that cons isted of a variable number of components in the CCSN and MCAN. The con figurations and conduction velocities of the shorter latency potential s were the same as those of the single compound action potentials evok ed by stimuli of 2 times threshold. Mean conduction velocities of the longer latency potentials were: CCSN = 24.4 +/- 2.6 m/s and MCAN = 24. 5 +/- 2.2 m/s. Needle electrode and direct stimulation of either the C CSN or the MCAN at 3 to 5 times threshold failed to evoke contractions of limb muscles. Therefore, action potentials that contributed to the evoked compound potentials recorded in these horses arose, most likel y, from afferent nerve fibers.