Antiarrhythmic effect of magnolol and honokiol during acute phase of coronary occlusion in anesthetized rats: Influence of L-NAME and aspirin

This study was designed to evaluate the in vivo effect of magnolol and hono kiol on the acute phase of coronary ligation in the presence of nitric oxid e inhibitor (L-NAME) or cyclooxygenase inhibitor (aspirin). After Sprague-D awley rats were anesthetized with urethane, the changes of ventricular arrh ythmia induced by coronary ligation for 30 min were determined with or with out pretreatment with study medications. The incidence and duration of vent ricular arrhythmia were significantly reduced after intravenous pretreatmen t (15 min before coronary ligation) with 10(-7) g/kg magnolol or 10(-7) g/k g honokiol. However, the antiarrhythmic effect of magnolol or honokiol coul d be abolished with the pretreatment of 1 mg/kg L-NAME, but not with pretre atment of 100 mg/kg aspirin. The abolishment of the myocardial beneficial e ffect of magnolol and honokiol by L-NAME, instead of aspirin, suggests an i nvolvement of an increased nitric oxide synthesis in the protection offered by magnolol and honokiol against arrhythmia during myocardial ischemia.