title: Anti-arrhythmic effect of kappa-opioid receptor stimulation in the perfused rat heart: involvement of a cAMP-dependent pathway.
abstract: During myocardial ischaemia the beta-adrenoceptor is activated, which contributes, at least partly, to cardiac arrhythmias via inducing [Ca2+]i oscillations. Since beta-adrenoceptor is negatively modulated by the kappa-opioid receptor in the heart, the present study attempted to determine if kappa-opioid receptor stimulation modulates the arrhythmogenic action of beta-adrenoceptor stimulation and to delineate the underlying mechanism. The effect of U50,488H, a selective kappa-opioid agonist, on arrhythmias in the isolated perfused rat heart subjected to low flow and 10(-6)mol/l norepinephrine (NE) were determined. Low flow induced arrhythmias, which were potentiated by NE, but not by 10(-6)mol/l U50,488H. The arrhythmia-potentiating effect of NE was antagonized by 10(-6)mol/l propranolol, a beta-adrenoceptor antagonist. U50,488H at 10(-6)mol/l also abolished the potentiation in arrhythmias by NE without affecting the arrhythmias induced by low flow. The anti-arrhythmic action of the kappa-opioid receptor agonist was abolished by 10(-6)mol/l nor-binaltorphimine, a selective kappa-opioid receptor antagonist, but not by 10(-7)mol/l calphostin C, an inhibitor of protein kinase C. Similarly, kappa-opioid receptor stimulation with U50,488H also abolished the NE-induced [Ca2+]i oscillations which are believed to cause cardiac arrhythmias, in ventricular myocytes. To determine whether the inhibitory actions of U50,488H against the effects of beta-adrenoceptor stimulation was via a cAMP-dependent or a cAMP-independent pathway, we determined the effects of U50,488H on NE-enhanced cAMP production and [Ca2+]i oscillations induced by either forskolin, an activator of adenylate cyclase, or Bay K-8644, a selective L-type Ca2+ channel agonist, in the ventricular myocytes. We found that U50,488H abolished the effect of forskolin, but did not alter the effect of Bay K-8644, on [Ca2+]i oscillations in the ventricular myocyte. In addition, U50, 488H also attenuated significantly the NE-induced elevation in cAMP in the heart. The observations suggest that kappa-opioid receptor stimulation abolishes the effect of beta-adrenoceptor stimulation on arrhythmias and [Ca2+]i oscillation via a cAMP-dependent pathway. The finding may be useful for the prevention and treatment of ischaemic heart diseases.
authors.affiliation: Faculty of Medicine, University of Hong Kong, Hong Kong.
authors.forename: X C
authors.initials: XC
authors.lastname: Yu
authors.forename: H X
authors.initials: HX
authors.lastname: Wang
authors.forename: J M
authors.initials: JM
authors.lastname: Pei
authors.forename: T M
authors.initials: TM
authors.lastname: Wong
mesh_terms: D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer / Q000494:pharmacology*; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000503:physiopathology*; D002118:Calcium / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004558:Electric Stimulation; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D006339:Heart Rate / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D000319:Adrenergic beta-Antagonists; D000889:Anti-Arrhythmia Agents; D017473:Receptors, Opioid, kappa; D005576:Colforsin; C051844:norbinaltorphimine; D009271:Naltrexone; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D011433:Propranolol; D000242:Cyclic AMP; D002118:Calcium; D009638:Norepinephrine