Evidence that the spasmogenic action of tetraethylammonium in guinea‐pig trachealis is both direct and dependent on the cellular influx of calcium ion

Abstract

Tetraethylammonium (TEA, 1–8 mmol/l) evoked spasm of guinea‐pig trachealis which was unaffected by atropine (1 μmol/l), mepyramine (1 μmol/l) or tetrodotoxin (3 μmol/l). The spasm evoked by TEA was markedly suppressed in Ca²⁺‐free Krebs solution while that evoked by acetylcholine was much less affected. Extracellular electrical recording showed that exposure to Ca²⁺‐free Krebs solution suppressed both spontaneous electrical slow wave activity of the trachea and the spasm and slow waves induced by TEA. These effects were reversible. TEA (2 and 8 mmol/1) increased the lanthanum‐resistant calcium fraction of trachea. It is concluded that TEA acts directly on the smooth muscle of guinea‐pig trachea, that the spasm and electrical slow waves evoked are Ca²⁺‐dependent and that the cellular influx of Ca²⁺ is increased.