Action of Tetraethylammonium Chloride on Neuromuscular Transmission in Frogs

Abstract

The action of tetraethylammonium chloride (TEA-Cl) on the neuromuscular transmission in frogs of 0.2–3 mm concentration was analyzed by recording a) the mechanical responses; b) direct action on the muscle fibers; c) end-plate potential (e.p.p.); d) direct action on the end-plate membrane; e) sensitivity of end-plate membrane to the applied ACh; f) the action potential of terminal endings of motor nerve fibers; g) direct action of nerve axon. TEA-Cl in these concentrations augments the e.p.p., and this augmentation increases with increasing concentrations. A relatively higher concentration (1–3 mm) depresses the e.p.p. after an initial augmentation. The sensitivity of the end-plate membrane to ACh is depressed by 0.2–3 mm. TEA-Cl in these concentrations acts on the terminal endings of motor nerve fibers and prolongs the negative after-potential of terminal endings. It is suggested that TEA-Cl increases the release of ACh by acting on the terminal endings, thus causing the augmentation of e.p.p.'s. The action of TEA-Cl at a given concentration will be determined by separate actions both on the end-plate membrane and the terminal ending of motor nerve fibers.