Alpha 2-adrenergic receptor agonist effects on supraventricular and ventricular automaticity in dogs with complete atrioventricular block.

摘要: Complete atrioventricular block was induced in 26 pentobarbital-anesthetized dogs to determine the effects of alpha 2-adrenergic receptor agonists, xylazine and medetomidine, on supraventricular ventricular automaticity. Prazosin atipamezole, alpha-adrenoceptor antagonists, were administered isolate 1- or 2-adrenoceptor effects. Six served as controls given glycopyrrolate (0.1 mg/kg body weight, IV) esmolol (50 75 micrograms/kg/min, induce parasympathetic beta 1-adrenergic blockade, respectively. Eight sequentially increasing doses (n = 5), 0.000257 mg (10(-9)M) 25.7 (10(-4)M) medetomidine 3), 0.000237 2.37 (10(-5)M) after blockade. Twelve 6, 1.1 mg/kg, 0.05 Three 3 prazosin followed by atipamezole (0.3 IV). The order reversed remaining either medetomidine. administration resulted stable rates over a 4-hour period. Increasing concentration did not cause significant changes rate. Xylazine presence (alpha 1) 2), rate.(ABSTRACT TRUNCATED AT 250 WORDS)