Electrophysiologic Effects of Isoproterenol and Beta Blocking Agents in Awake Dogs

摘要: In awake, unrestrained animals beta adrenergic stimulation by isoproterenol increased heart rate and enhanced A-V conduction with no change of in Purkinje tissue or ventricular activation time. The chronotropic dromotropic responses to were abolished completely the antagonists, propranolol (0.2 mg/ kg) pronethalol (2 mg/kg). Beta blockade produced significant rate, conduction, velocity tissue, contrast above, tachycardia, prolonged slightly. tachycardia which followed was largely a consequence vagal inhibition since it could be nearly prior administration atropine. Propranolol changes refractory period excitability atrial muscle. Pronethalol did not alter muscle but prolong period. Barbiturate anesthesia found time, anesthetized both caused further depression conduction. These data support view that cardiac activity has little influence on ventricle, suggest intensity sympathetic dogs is minimal. differences unanesthetized indicate latter agent anticholinergic properties as well certain extra-adrenergic actions Failure blocking doses above agents diastolic thresholds indicates their anti-arrhythmic are related an effect excitability. appear exert qualitatively quantitatively different effects awake preparations, observation should taken into consideration when evaluating pharmacologic these compounds.