الفهرس 
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Abstract
This thesis was designed to evaluate the antiarrhythmic effects of NO precursor (Larginine) in conscious rabbits against epinephrine and aconitine induced arrhytmia, and also to evaluate the effect of NO precursor and NO inhibitor on the antiarrhythmic effect of propranolol and verapamil against epinephrine and aconitine induced arrhythmia. Intravenous injection of 30 <U+F06D>g/kg epinephrine produced biphasic effect consisting of an initial phase of bradycardia immediately observed after epinephrine administration, followed by second phase of cardiac acceleration showing extrasystoles and ventricular tachycardia. The intravenous injection of 30 <U+F06D>g/kg aconitine produced on initial phase of bradycardia followed by ventricular extrasystoles, supraventricular tachycardia, ventricular tachycardia and ventricular fibrillation. Death of all animals accrued from ventricular fibrillation in about 10 minutes. Effect of Larginine in doses (50, 100, 150, and 200 mg/kg i.v.) on cardiac arrhythmia induced by epinephrine (30 <U+F06D>g/kg i.v. ) or aconitine (30 <U+F06D>g/kg i.v. ) Larginine in a dose 200 mg/kg produced protection 80% from ventricular extrasystoles and ventricular tachycardia, and also produced 60% protection from ventricular tachycardia and ventricular fibrillation. LNAME in (7.5 mg/kg.) intravenously injection produced increasing in the ventricular tachycardia and ventricular fibrillation induced by epinephrine and aconitine respectively. Larginine (50, 100, and 150 mg/kg i.v.) produced dose dependent protection from arrhythmia. In the light of these results. We can conclude that Larginine possesses antiarrhythmic activity and enhances synergistic the antiarrhythmic effect of propranolol and verapamil and further study should be done to evaluate these result clinically.