title: Effects of diltiazem and other Ca2+ antagonists on guinea-pig tracheal muscle.
abstract: The effects of diltiazem and 3 other Ca2+ antagonists (verapamil, nicardipine, bepridil) were studied on isolated guinea-pig tracheal preparations which were contracted with several agonists. Assessment of the contractile agonists was performed under physiological conditions as well as in Ca2+-depleted solutions. The order of potency of the contractile agonists was LTD4 greater than ACh greater than 5-HT greater than Hist greater than BaCl2 greater than TEA greater than KCl. The efficacy of the physiological agonists ACh, Hist and LTD4 was moderately depressed in Ca2+-free solutions while the responses to non-specific agonists and 5-HT were markedly reduced. Diltiazem and verapamil reduced basal tone at concentrations greater than or equal to 10(-4) M. Diltiazem displaced all agonist concentration-effect curves to the right. The four Ca2+ antagonists studied had a marked effect on non-physiological agonists as compared to that on physiological agents. Increasing Ca2+ concentration only partially reversed the inhibitory effect of diltiazem.
mesh_terms: D000403:Airway Resistance / Q000187:drug effects*; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D004110:Diltiazem / Q000494:pharmacology*; D004347:Drug Interactions; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects; D014132:Trachea / Q000187:drug effects
chemical_list: D001552:Benzazepines; D002121:Calcium Channel Blockers; D004110:Diltiazem; D002118:Calcium