Pre- and Postsynaptic Actions of Tetraethylammonium at the Chick Neuromuscular Junction

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Abstract
The possible pre- and postsynaptic effects of tetraethylammonium (TEA; a K+ channel blocker) were examined in the isolated chick neuromuscular junction. The presynaptic effect of TEA was studied by investigating its effect on the utpake of [3H]choline, 3H-methyl choline, which was taken as an index of acetylcholine (ACh) release. The postsynaptic effect of TEA was investigated using solutions containing no Ca2+ and/or Ca antagonist La. TEA increased the uptake of [3H]choline by a factor of 10. Although the contracture produced by TEA was greatly reduced by La (0.1-1 .mu.M), it still persisted in the Ca-free Krebs solution.