Interaction between Repetitive Nerve Stimulation and Twitch-potentiating Agents at the Neuromuscular Junction

Abstract

THE indirectly developed maximal twitch tension of vertebrate muscle is sometimes augmented after periods of tetanic nerve stimulations an effect generally called post-tetanic potentiation. This effect is further increased by the administration, prior to tetanic conditioning, of physostigmine in doses which in themselves are too small to facilitate twitch tension¹. Physostigmine² and also other agents which elicit twitch potentiation, for example neostigmine³ and m-hydroxy phenyltrialkylammonium ions⁴, have been shown to possess an action on motor nerve terminals which is revealed by bursts of repetitive antidromic nerve discharge appearing after single orthodromic volleys. Furthermore, this presynaptic activity is greatly facilitated by tetanic conditioning of the motor nerve⁵. Within the context of these observations, it seemed important to compare drug-induced twitch potentiation before and after periods of repetitive motor nerve stimulation.