The first report that an OR agonist has an antiarrhythmic effect was with meptazinol during coronary artery occlusion in rats in 1983.235 In 1989, it was shown that the selective μ OR agonist fentanyl (60 μg/kg intravenously) increased the ventricular fibrillation threshold (VFT) in dogs with coronary artery occlusion.236 The μ and κ OR agonist buprenorphine had the same effect.236 The antifibrillatory activity of the μ OR agonists fentanyl, sufentanil, and carfentanil in dogs with coronary artery occlusion was demonstrated by Hess et al. The gene discussed is OPRM1; the disease is ventricular fibrillation.