title: Effects of nicardipine and diltiazem on alpha-adrenoceptor responses in canine saphenous veins.
abstract: The effects of calcium antagonists, diltiazem and nicardipine (-6.0 to -4.0 log mol/l), on the contractile responses to noradrenaline, methoxamine and BHT-920 in isolated canine saphenous vein rings, were studied with isometric tension recordings. Concentration-effect curves to the alpha-agonists were obtained in the control state and in the presence of diltiazem or nicardipine. Propranolol (-6.0 log mol/l) was present in the bath throughout. Diltiazem had no significant inhibitory effect on the responses mediated by all three agonists. Nicardipine (-5.0 and -4.0 log mol/l) produced a small but significant inhibitory effect on the responses to noradrenaline and methoxamine while it had no effect on the response to BHT-920. The effects of nicardipine were greatest on the responses to methoxamine. These calcium antagonists appeared to have only small post-synaptic inhibitory effects on the contractile responses to alpha-agonists in the canine saphenous vein with nicardipine exerting a greater inhibitory influence than diltiazem.
mesh_terms: D000818:Animals; D001381:Azepines / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology*; D004285:Dogs; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009529:Nicardipine / Q000494:pharmacology*; D009638:Norepinephrine / Q000494:pharmacology; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D012501:Saphenous Vein / Q000187:drug effects
chemical_list: D001381:Azepines; D011942:Receptors, Adrenergic, alpha; C024763:talipexole; D009529:Nicardipine; D004110:Diltiazem; D008729:Methoxamine; D009638:Norepinephrine