INDUCTION OF NONSPECIFIC AIRWAY HYPERREACTIVITY BY POTASSIUM CHANNEL BLOCKADE IN RAT ISOLATED TRACHEA

1. The exposure of rat isolated tracheal segment to the K+-channel inhibitor tetraethylammonium (TEA, 10 mM) for a period of 10-15 min generally produced little or no contractile response. 2. Cooling (10°C) provocation alone usually produced small (10 ± 3% acetylcholine maximum) contractile responses. 3. In the presence of TEA (10 mM, 10-15 min exposure), rat trachea exhibited airway hyperreactivity to acetylcholine, 5-hydroxytryptamine (5-HT) and cooling. It also increased the peak tension induced by 5-HT. 4. TEA-induced airway hyperreactivity to cooling was significantly inhibited in Ca2-free Krebs solution suggesting an important role for extracellular Ca2+ influx. 5. We conclude that the blockade of potassium channels with TEA induces non-specific airway hyperreactivity to cooling, 5-HT and acetylcholine in rat isolated tracheal segments.