[The role of opiate receptors and ATP-dependent potassium channels of mitochondria in the formation of myocardial adaptive resistance to the arrhythmogenic effect of ischemia and reperfusion]. / Rol' opiatnykh retseptorov i ATF-zavisimykh kalievykh kanalov mitokhondrii v formirovanii adaptatsionnoi ustoichivosti miokarda k aritmogennomu deistviiu ishemii i reperfuzii.

Preliminary stimulation of opiate receptors (ORs) by intravenous administration of mu agonist DALDA (0.5 mg/kg), delta 1 agonist DPDPE (0.5 mg/kg), and kappa agonist (-)-U-50.488 (1 mg/kg) increases rat myocardial resistance to arrhythmogenic effect of coronary occlusion (10 min) and reperfusion (10 min). Activation of delta 2 ORs (DSLET, 0.5 mg/kg) has no effect on the incidence rate of ischemic and reperfusion arrhythmias. Preliminary administration of glibenclamide (0.3 mg/kg), an inhibitor of KATP channels, blocks the antiarrhythmic effect of DALDA and DPDPE. Repeated short-term exposures of rats to immobilization within two weeks increases the heart tolerance to the arrhythmogenic effect of coronary occlusion and reperfusion. This effect disappears after administration of CTAP (0.5 mg/kg), a mu antagonist, or injection of 5-hydroxydecanoate (5 mg/kg), an inhibitor of mitochondrial KATP channels. The selective antagonists of delta and kappa ORs have no effect on cardiac adaptation-induced resistance to the arrhythmogenic effect of ischemia and reperfusion. We believe that stimulation of mu, delta, and kappa ORs increases myocardial tolerance to the arrhythmogenic effect of ischemia and reperfusion through activation of KATP channels. The antiarrhythmic effect of the adaptation is mediated by stimulation of mu ORs and mitochondrial KATP channels.

Endogenous cannabinoids improve myocardial resistance to arrhythmogenic effects of coronary occlusion and reperfusion: a possible mechanism.

Stimulation of cannabinoid receptors with endogenous cannabinoid anandamide and its enzyme-resistant analogue R-(+)-methanandamide improved cardiac resistance to arrhythmias induced by coronary occlusion and reperfusion. This antiarrhythmic effect was not associated with activation of NO synthase, since pretreatment with NG-nitro-L-arginine methyl ester had no effect on the incidence of ischemia/reperfusion-induced arrhythmias. Blockade of ATP-dependent K+ channels with glybenclamide did not abolish the antiarrhythmic effect of R-(+)-methanandamide. Antiarrhythmic activity of endogenous cannabinoids is probably associated with their direct effects on the myocardium.

[Interactions of peripheral mu-opioid receptors and K(ATP)-channels in regulation of cardiac electrical stability in ischemia, reperfusion, and postinfarction cardiosclerosis]. / Vzaimodeistvie perifericheskikh mu-opiatnykh retseptorov i K(ATF)-kanalov v reguliatsii élektricheskoi stabil'nosti serdtsa pri ishemii, reperfuzii i postinfarktnom kardioskleroze.

It has been shown that mu-opioid receptor stimulation by intravenous administration of the selective mu receptor agonist DALDA in a dose of 0.1 mg/kg prevented ischemic and reperfusion arrhythmias in rats subjected to coronary artery occlusion (10 min) and reperfusion (10 min), and also increased the ventricular fibrillation threshold in rats with postinfarction cardiac fibrosis. These effects were abolished by pre-treatment with the selective mu receptor antagonist CTAP in a dose of 0.5 mg/kg or by prior injection of the opioid receptor antagonist naloxone methiodide (2 mg/kg) which does not penetrate the blood-braib barrier. Both antagonists by themselves had no effect on the incidence of occlusion or reperfusion-induced arrhythmias or on the ventricular fibrillation threshold. Pre-treatment with ATP-sensitive K+ channel (KATP channel) blocker glibenclamide in a dose of 0.3 mg/kg completely abolished the antiarrhythmic effect of DALDA. We believe that DALDA prevents occurrence of electrical instability during ischemia and reperfusion and increases the ventricular fibrillation threshold in rats with postinfarction cardiac fibrosis via stimulation of peripheral mu-opioid receptor which appear to be coupled to the KATP channel.

[Stimulation of delta1-opioid receptors increases the ventricular fibrillation threshold in post-infarct cardiosclerosis: the role of K(ATP)-channels]. / Stimuliatsiia del'ta1 opioidnykh retseptorov povyshaet porog zheludochkovoi fibrilliatsii pri postinfarktnom kardioskleroze: rol' K(ATP)-kanalov.

Preliminary administration of the delta 1-opioid receptor (delta 1-OR) selective peptide agonist DPDPE (0.1 mg/kg, i.v.) increased the ventricular fibrillation threshold (VFT) in postinfarction cardiosclerosis in rats. Pretreatment with the selective delta 1-OR antagonists ICI 174,864 (not affecting VFT) in a dose of 0.5 mg/kg completely eliminated the DPDPE-induced increase in the VFT. Pretreatment with the KATP channel selective blocker glibenclamide (0.3 mg/kg, i.v.) completely eliminated the delta 1-OR mediated increase in the VFT protective effect of the delta 1-OR stimulation. The intravenous injection of the mitochondrial KATP channel blocker 5-hydroxydecanoate (5 mg/kg) simultaneously with DPDPE not only eliminated the delta 1-OR mediated increase on VFT, but additionally increased the VBFT drop caused by cardiosclerosis. Injected separately, neither glibenclamide nor hydroxydecanoate affected the VFT level. It is concluded that stimulation of the delta 1-OR increases VFT by activating mitochondrial KATP-channels.

Endogenous cannabinoid anandamide increases heart resistance to arrhythmogenic effects of epinephrine: role of CB(1) and CB(2) receptors.

Intravenous injection of 10 mg/kg anandamide reduces the incidence and duration of epinephrine-induced arrhythmias in rats. SR141716A and SR144528, antagonists of cannabinoid receptor I and II did not abolish the antiarrhythmic effect of anandamide. These data suggest that the antiarrhythmic effect of anandamide is nonspecific or mediated via unknown cannabinoid receptors, but not associated with activation of cannabinoid receptors I and II.