title: Interaction between Bay-K-8644 and various relaxant agents on K+-depolarized contracture of guinea pig taenia coli.
abstract: 1. Interaction between Bay-K-8644 and nifedipine, D600, diltiazem, papaverine or W-7 on a K+-contracture of the guinea pig taenia coli have been investigated. 2. These relaxing drugs except Bay-K-8644 inhibited the K+-contracture in a concentration-dependent manner. 3. Complete inhibition by nifedipine (1 x 10(-7) M) of the contracture was absolutely antagonized by Bay-K-8644 (1 x 10(-6) M), a Ca2+-agonist, an apparent pA2 value of Bay-K-8644 as an antagonist for nifedipine obtained from Schild plot being 7.94 and its slope 0.99. 4. Marked inhibitions by D600 (1 x 10(-5) M), diltiazem (1 x 10(-5) M), papaverine (1 x 10(-4) M) and W-7 (1 x 10(-4) M) were unaffected but mild inhibitions by around IC50 of these relaxing agents, except W-7, were fully antagonized by Bay-K-8644. 5. These results suggest that Bay-K-8644 is a competitive antagonist for nifedipine, but not for other agents, on common Ca2+ channel sites.
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D003106:Colon / Q000187:drug effects; D004095:Dihydropyridines / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D000431:Ethanol / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects*; D009543:Nifedipine / Q000494:pharmacology; D010208:Papaverine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology
chemical_list: D004095:Dihydropyridines; D009125:Muscle Relaxants, Central; D005711:Gallopamil; D000431:Ethanol; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D010208:Papaverine; D004110:Diltiazem; D009543:Nifedipine; D011188:Potassium