title: Electromechanical effects of tetraethylammonium and K+ on histamine-induced contraction in pig isolated tracheal smooth muscle.
abstract: The effect of tetraethylammonium (TEA) and K+ on contractions to histamine and acetylcholine have been compared in the pig isolated trachea using organ bath and sucrose-gap techniques. Histamine elicited weak contractions, compared with acetylcholine; however, these contractions were markedly potentiated by pretreatment with TEA (10 mM) or by raising the external KCl concentration to 30-50 mM. Neither TEA nor K+ increased the sustained depolarization evoked by histamine (or acetylcholine) although oscillatory depolarizations were often observed in the presence of TEA. Verapamil and a zero Ca2+ Krebs solution reduced contractions to histamine and reduced or abolished the effect of TEA and K+ on histamine-induced contractions. The results unmask different mechanisms of contraction for histamine and acetylcholine. Histamine-induced tone appears to be linked with mechanisms sensitive to TEA and high K+, possibly involving increased translocation of Ca2+ across the plasma membrane.
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D002118:Calcium / Q000502:physiology; D006632:Histamine / Q000494:pharmacology*; D006633:Histamine Antagonists; D066298:In Vitro Techniques; D011188:Potassium / Q000494:pharmacology*; D013395:Sucrose; D013552:Swine; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D006633:Histamine Antagonists; D013757:Tetraethylammonium Compounds; D013395:Sucrose; D019789:Tetraethylammonium; D006632:Histamine; D014700:Verapamil; D000109:Acetylcholine; D011188:Potassium; D002118:Calcium