The effects of intraventricular atropine on the heart rate was investigated in the rabbit. Intraventricular administration of atropine in a dose of 10, 30, 100, or 300 ug produced dose dependant bradycardia. Atropine (100 ug) induced bradycardia was abolished by bilateral vagotomy or intravenous atropine, and inhibited by intravenous propranolol but not by intravenous Regitine. Intraventricular Ecolid or regitine pretreatment diminished the bradycardia induced by intraventricular atropine. From the above results, it is suggested that a central adrenergic mechanism as well as vagal activity plays an important role in the intraventricular atropine-induced bradycardia.
Atropine* ; Bradycardia ; Chlorisondamine ; Heart Rate* ; Heart* ; Phentolamine ; Propranolol ; Vagotomy