During aconitine-induced arrhythmias the antiarrhythmic effect of DALDA (Tyr-D-Arg-Phe-Lys-NH2) and nociceptin (orphanin FQ) administered intravenously depended on activation of nitric oxide synthase. K(ATP) channels were not involved in the realization of this effect. Endogenous prostanoids played a minor role in the antiarrhythmic effect of nociceptin and did not contribute to the protective influence of DALDA. The antiarrhythmic effect of orphanin FQ administered intravenously did not depend on functional activity of the autonomic nervous system. However, the effect of orphanin FQ after intracerebroventricular infusion was determined by changes in the state of this system.