NEUROMUSCULAR FACILITATION AND ANTIDROMIC DISCHARGES IN MOTOR NERVES: THEIR RELATION TO ACTIVITY IN MOTOR NERVE TERMINALS

Abstract

Intra-arterial injection of physostigmine or hydroxyanilinium ions elicits postactivation retrograde discharges. A conditioning stimulus greatly facilitates antidromic activity in ventral root fibers when the test stimulus is applied within 4 msec. Following the period of facilitation, retrograde activity remains suppressed for 50 to 160 msec, after the conditioning stimulus. During this interval, a test stimulus does not elicit muscle repetition and transmission may be marginal. It is suggested that motor nerve terminals as site of origin of the antidromic activity are capable of sustaining, in the presence of the agents used, negative and positive after potentials of a time course similar to that of fibers of slow conduction velocity.