title: Effects of five different organic calcium antagonists on guinea-pig isolated trachea.
abstract: The relaxant effects of five organic calcium antagonists (nicardipine, diltiazem, PY 108068, verapamil and bepridil) on guinea-pig isolated trachea were tested against contractions induced by acetylcholine, histamine, 5-hydroxytryptamine, potassium chloride (KCl) and tetraethylammonium (TEA) in a medium containing the normal amount of calcium and against calcium dose-response curves in a calcium-free, potassium-enriched medium. These effects were compared with those of spasmolytic or specific acetylcholine or histamine antagonists. In contrast to the other drugs tested, organic calcium antagonists exerted a specific inhibitory effect on KCl- and TEA-induced contractions. Their degree of activity was in the order: nicardipine greater than diltiazem greater than PY 108068 greater than verapamil greater than bepridil. All calcium antagonists inhibited calcium dose-response curves at similar concentrations. Organic calcium antagonists therefore seem to exert a specific inhibitory effect on depolarizing agents in the guinea-pig isolated trachea, unlike other tissues, notably some vascular smooth muscles.
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology; D015764:Bepridil; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D009529:Nicardipine; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D011759:Pyrrolidines / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects; D014700:Verapamil / Q000494:pharmacology
chemical_list: D000889:Anti-Arrhythmia Agents; D002121:Calcium Channel Blockers; D011759:Pyrrolidines; D015764:Bepridil; D014700:Verapamil; D009529:Nicardipine; D004110:Diltiazem; D009543:Nifedipine; C034600:darodipine