title: U50,488H inhibits effects of norepinephrine in rat cardiomyocytes-cross-talk between kappa-opioid and beta-adrenergic receptors.
abstract: In order to determine the effect of kappa-opioid receptor agonist on the beta1-adrenoceptor stimulation in the heart, the effects of norepinephrine (NE), a beta1-adrenoceptor agonist, on contraction and electrically induced intracellular calcium ([Ca2+]i) transient in the single rat ventricular myocyte pretreated with a kappa-opioid receptor agonist, trans-(+/-)-3, 4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)-benzeneacetamide (U50,488H), at 0.01-1 microM were studied with a video edge tracker method and a spectrofluorometric method using fura-2 as calcium indicator, respectively. NE at 0.01-10 microM augmented both twitch amplitude and electrically induced [Ca2+]i transient dose-dependently, which were abolished by propranolol at 1 microM, a beta-adrenoceptor antagonist. The effects of NE on both contraction and [Ca2+]i transient were attenuated in a dose-dependent manner by U50,488H at 0.01-1 microM, which itself had no effect at all. The maximum response ( Emax) was decreased, while the concentration that produces 50% of the maximum response (EC50) was enhanced, by U50, 488H. The inhibitory effects of U50,488H on beta-adrenoceptor stimulation were completely blocked by pretreatment with norbinaltorphimine, a specific kappa-opioid receptor antagonist at 1 microM, or preincubation with pertussis toxin (PTX) at 200 ng/ml for 6 h. On the other hand, the inhibition on NE-induced augmentation in electrically induced [Ca2+]i transient by U50,488H was not affected by pretreatment with U73122, a specific inhibitor of phospholipase C (PLC), at 10 microM for 30 min. U50,488H attenuated the augmentation of the electrically stimulated [Ca2+]i transient induced by forskolin at 0.1 and 0.5 microM. It did not, however, affect the augmentation of the electrically induced [Ca2+]i transient by N6, 2'-O-dibutyryl adenosine cyclic monophosphate (DB-cAMP). The results suggest that kappa-opioid receptor stimulation by U50,488H at 10(-6 )M or lower may inhibit the effects of beta-adrenoceptor stimulation by acting at a PTX-sensitive G-protein and AC, but not via the phosphoinositol pathway.
authors.affiliation: Department of Physiology and Institute of Cardiovascular Science and Medicine, Faculty of Medicine, The University of Hong Kong, Hong Kong.
authors.forename: X C
authors.initials: XC
authors.lastname: Yu
authors.forename: H Y
authors.initials: HY
authors.lastname: Li
authors.forename: H X
authors.initials: HX
authors.lastname: Wang
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*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D005576:Colforsin / Q000494:pharmacology; D004558:Electric Stimulation; D019204:GTP-Binding Proteins / Q000378:metabolism; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009271:Naltrexone / Q000031:analogs & derivatives / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D037342:Pertussis Toxin; D051381:Rats; D017207:Rats, Sprague-Dawley; D011943:Receptors, Adrenergic, beta / Q000187:drug effects* / Q000378:metabolism; D017473:Receptors, Opioid, kappa / Q000819:agonists / Q000037:antagonists & inhibitors / Q000187:drug effects*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D000318:Adrenergic beta-Agonists; D011943:Receptors, Adrenergic, beta; D017473:Receptors, Opioid, kappa; D010566:Virulence Factors, Bordetella; D005576:Colforsin; C051844:norbinaltorphimine; D009271:Naltrexone; D003994:Bucladesine; D019900:3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium; D009638:Norepinephrine