The actions of tetraethylammonium at the neuromuscular junction

1. Tetraethylammonium (TEA) produces contractures in slow muscle fibres of the chick and the guinea-pig. 2. These contractures probably involve (a) the facilitation of the release of acetylcholine by TEA (b) direct stimulant action of TEA on the post-synaptic membrane with little accompanying depolarization. 3. Since microelectrode studies on fast twitch fibres indicate that TEA exerts a blocking action on the Na+/K+ ion channel of the end-plate it may be that TEA produces its direct contracture-inducing action in slow fibres by increasing Ca2+ influx.