Pre- and postsynaptic actions of tetraethylammonium at the chick neuromuscular junction.

The possible pre- and postsynaptic effects of tetraethylammonium (TEA; a potassium ion channel blocker) have been examined in the isolated chick neuromuscular junction. The presynaptic effect of TEA was studied by investigating its effect on the uptake of tritiated 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 calcium ions and/or calcium antagonist lanthanum. TEA increased the uptake of tritiated choline by a factor of 10. Although the contracture produced by TEA was greatly reduced by lanthanum (0.1-1 microM), it still persisted in the calcium-free Krebs solution.