The effects of tetraethylammonium and other agents on the potassium mechanoreceptor current in the ciliate Stylonychia.

The membrane response to mechanical stimulation was investigated under voltage-clamp conditions in the hypotrich ciliate Stylonychia mytilus (Protozoa). The mechanoreceptor current shows high ionic selectivity, unlike than in metazoans. It is exclusively carried by potassium ions and is selectively inhibited by tetraethylammonium and 4-aminopyridine. Procaine, tetramethylammonium, caesium and divalent cations have no or little effect on this receptor current. The ionic channels mediating the currents differ from voltage-dependent channels in the ciliate membrane in their low sensitivity to divalent cations, and their relatively high sensitivity to tetraethylammonium and 4-aminopyridine.