Effects of intracellular or extracelluar application of tetraethylammonium on the action potential in cultured chick embryonic heart muscle cell.

The effects of tetraethylammonium (TEA) on the action potential in cultured chick embryonic heart muscle cells were investigated. The onset of prolongation of the action potential occurred within 10 min following intracellular iontophoretic application of TEA, but after more than 50 min following extracellular application. These facts suggest the major site of action of TEA is on the inner surface of the membrane these cells.