BACKGROUND: The experiment was performed to determine the role of kappa-opioid receptor (OR) agonist U50488H given at early reperfusion. METHODS: Isolated hearts were subjected to 30 minutes of regional ischemia and 120 minutes of reperfusion.Hearts were assigned randomly to one of the three groups:1) Control (n = 9), 2) U50-1 (n = 8); 10micrometer of U50488H, and 3) U50-10 (n = 8); 10micrometer of U50488H.U50488 was perfused for a period of 5 min before and 30 min after reperfusion. RESULTS: U50488H significantly reduced infarct size as a percentage of ischemic area (12.2 +/- 1.9% in U50-1 and 7.2 +/- 1.7% in U50-10, P < 0.001) compared to the control hearts (27.2 +/- 1.2%). After 2 hrs of reperfusion, left ventricular developed pressure was significantly recovered by U50488H (62.6 +/- 5.7% in U50-1 and 68.6 +/- 4.7% in U50-10, P = 0.018 and 0.002, respectively) compared to the control (46.3 +/- 4.4%).Rate-pressure product was improved by 100micrometer U50488H (62.3 +/- 5.5%, P = 0.007) but not by 1micrometer U50488H (50.0 +/- 4.1%) compared to the control (44.7 +/- 4.5%).U50488H significantly increased the + dP/dt(max) (77.9 +/- 5.5% in U50-1 and 78.0 +/- 4.3 in U50-10, P = 0.005 and 0.001 vs. control, respectively).The -dP/dt(min) also improved by 10micrometer U50488H (64.7 +/- 4.8%, P = 0.003) compared to control (47.0 +/- 2.7%). CONCLUSIONS: U50488H given at early reperfusion phase reduces both infarct size and myocardial stunning in isolated rat hearts.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; Animals ; Heart ; Ischemia ; Myocardial Stunning ; Myocardium ; Rats ; Receptors, Opioid ; Reperfusion

Opioid receptors have been pharmacologically classified as micro, delta, kappa and epsilon. We have recently reported that the antinociceptive effect of morphine (a micro-opioid receptor agonist), but not that of beta-endorphin (a novel micro/epsilon-opioid receptor agonist), is attenuated by whole body irradiation (WBI). It is unclear at present whether WBI has differential effects on the antinociceptive effects of micro-, delta-, kappa- and epsilon-opioid receptor agonists. In our current experiments, male ICR mice were exposed to WBI (5Gy) from a 60Co gamma-source and the antinociceptive effects of opioid receptor agonists were assessed two hours later using the hot water (52degrees C) tail-immersion test. Morphine and D-Ala2,N-Me-Phe4,Gly-olenkephalin(DAMGO), [D-Pen2-D-Pen5]enkephalin (DPDPE), trans-3,4-Dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]-benzeneacetamide (U50,488H), and beta-endorphin were tested as agonists for micro, delta, kappa, and epsilon-opioid receptors, respectively. WBI significantly attenuated the antinociceptive effects of morphine and DAMGO, but increased those of beta-endorphin. The antinociceptive effects of DPDPE and U50,488H were not affected by WBI. In addition, to more preciously understand the differential effects of WBI on micro- and epsilon-opioid receptor agonists, we assessed pretreatment effects of beta-funaltrexamine (beta-FNA, a micro-opioid receptor antagonist) or beta-endorphin1-27 (beta-EP1-27, an epsilon-opioid receptor antagonist), and found that pretreatment with beta-FNA significantly attenuated the antinociceptive effects of morphine and beta-endorphin by WBI. beta-EP1-27 significantly reversed the attenuation of morphine by WBI and significantly attenuated the increased effects of beta-endorphin by WBI. The results demonstrate differential sensitivities of opioid receptors to WBI, especially for micro- and epsilon-opioid receptors.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; Animals ; beta-Endorphin ; Enkephalin, Ala(2)-MePhe(4)-Gly(5)- ; Enkephalin, D-Penicillamine (2,5)- ; Humans ; Male ; Mice ; Mice, Inbred ICR ; Morphine ; Naltrexone ; Receptors, Opioid ; Water ; Whole-Body Irradiation

BACKGROUND: Previous reports have described that the local administration of opioid receptor agonist can attenuate the nociceptive responses induced by a variety of inflammatory states. This study evaluated the effects of mu or kappa opioid receptor agonists peripherally administered at a site of injury on the state of thermal hyperalgesia induced by mild burn injury. METHODS: Thermal injury was induced after briefly anesthetizing with halothane, by applying the left hindpaw to a hot plate (52.5 degree C) for 45 seconds. Paw withdrawal latency of the hindpaw was determined using an underglass thermal stimulus, which allowed the response latency of the injured paw to be obtained. In this work, the mu receptor agonist, morphine (10, 30, 100 microgram), or the kappa receptor agonist, U50,488H (10, 30, 100 microgram), was administered respectively at the injured site on the right hindpaw in rats. To compare the systemic effects of the drug, the same drug was administered at the normal left hindpaw site with mild burn injury. Naloxone (40 microgram/kg) was administered at the injured site or at the normal site to determine the reversibility of the opioid used. RESULTS: Mild burn injury produced thermal hyperalgesia manifested as reduced paw withdrawal latency. Administration of either morphine (10, 30, 100 microgram) or U50,488H (10, 30, 100 microgram) at the injured site attenuated hyperalgesia in a dose-dependent manner. But the administration of drugs at the normal site had no effect on hyperalgesia at the injured site. In addition, naloxone had the effect of morphine and U50,488H reversed significantly. CONCLUSIONS: These results suggest that peripheral mu or kappa opioid receptor administration at an injured site may play an important role in the hyperalgesia induced by mild burn injury.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; Animals ; Burns ; Halothane ; Hyperalgesia* ; Morphine ; Naloxone ; Rats* ; Reaction Time ; Receptors, Opioid ; Receptors, Opioid, kappa* ; Receptors, Opioid, mu

OBJECTIVETo investigate the interaction between opioid receptor (OR) stimulation and adrenergic receptor (AR) stimulation in the isolated ischaemia/reperfusion (I-R) rat heart.

METHODSMale Sprague-Dawley rats were used for Langendoff isolated heart perfusion. Myocardial ischemia for 20 min was followed by 30 min of reperfusion, during which the kappa-OR agonist U50488h and beta(1)-AR agonist norepinephrine (NE) were administered.

RESULTS(1) 50488h antagonized the effect of NE in rising left ventricular systolic pressure (LVSP) in the early phase of myocardial ischemia at 10, 20, 30 min of reperfusion. (2) Arrhythmia scores in the I-R+NE+U50488h group were markedly lower than those in the I-R group during the 10 - 20 min reperfusion period. No significant differences in arrhythmia scores were found in either I-R+U50488h or I-R+NE group when compared with I-R group. (3) Compared with the I-R group, U50488h alone or plus NE decreased reperfusion heart rates after myocardial ischemia while NE alone showed no effect.

CONCLUSIONIt is suggested that the interaction in the signaling pathway between kappa-OR and beta(1)-AR occurred during myocardial I-R of rat heart.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; pharmacology ; Animals ; Male ; Myocardial Reperfusion ; Norepinephrine ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, Adrenergic ; physiology ; Receptors, Opioid, kappa ; physiology ; Signal Transduction ; physiology

BACKGROUND: We investigated whether p42/p44 extracellular signal-regulated kinases (ERK1/2) and/or phosphatidylinositol-3-OH kinase (PI3K)-Akt play a crucial role in cardioprotection by kappa-opioid receptor (KOP) activation. METHODS: Langendorff perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Antagonists of ERK1/2 and PI3K were perfused in hearts treated with the KOP agonist U50488H (U50). Infarct size was measured after 2 h of reperfusion. The phosphorylation states of ERK1/2 and Akt by Western immunoblots were determined. Drugs were perfused for a period of 5 min before and 30 min after reperfusion. RESULTS: Inhibition of ERK1/2 (26.8 +/- 2.9%, P < 0.05 vs. U50) but not PI3K (15.5 +/- 1.1%, P > 0.05 vs. U50) completely abrogated the anti-infarct effect of U50488H. Western blot analysis revealed a significant increase in ERK1/2 but not Akt phsophorylation in U50488H-treated hearts as compared to control hearts when measured immediately after reperfusion. CONCLUSIONS: KOP activation effectively reduces myocardial infarction. The anti-infarct effect of U50488H is mediated by the ERK1/2, but not the PI3K-Akt pathway.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; Animals ; Blotting, Western ; Coronary Occlusion ; Extracellular Signal-Regulated MAP Kinases ; Heart ; Ischemia ; Myocardial Infarction ; Phosphatidylinositol 3-Kinases ; Phosphorylation ; Rats ; Receptors, Opioid ; Reperfusion

To investigate the relaxation effect and underlying mechanism of U50,488H (a selective kappa-opioid receptor agonist) on aorta in the rat, isolated aortic ring was perfused and the tension of the vessel was measured. It was shown: (1) kappa-opioid receptor stimulation with U50,488H relaxed rat aorta dose-dependently; (2) the relaxation effect of U50,488H on aorta was partially endothelium-dependent; (3) the relaxation effect of U50,488H was significantly attenuated in the presence of glybenclamide and glipizide, two ATP-sensitive K(+) channel (K(ATP)) blockers; and (4) the relaxation effect of U50,488H on vessel bore no relationship to muscarinic-receptor, beta-adrenoceptor, prostaglandin and nitric oxide (NO). These results indicate that kappa-opioid receptor stimulation with U50,488H relaxes the aortic artery at least partially via K(ATP) channel in the rat.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; pharmacology ; Animals ; Aorta ; physiology ; In Vitro Techniques ; KATP Channels ; metabolism ; Male ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, kappa ; agonists ; physiology ; Vasodilation ; physiology

OBJECTIVETo observe the effect of κ-opioid receptor (κ-OR) stimulation on Angiotensin II (Ang II)-induced cardiomyocyte hypertrophy in vitro cultured myocardial cells from neonatal rats and on calcineurin (CaN) signal pathways.

METHODSCultured myocardial cells of neonatal rats were divided into control group, CSA (1 µmol/L) group, Ang II (1 µmol/L) group, Ang II (1 µmol/L) + U50488H (1 µmol/L) group, Ang II (1 µmol/L) + CSA (1 µmol/L) group, Ang II (1 µmol/L) + Rp-cAMPS (1 µmol/L) group, Ang II (1 µmol/L) + CSA (1 µmol/L) + U50488H (1 µmol/L) group and Ang II (1 µmol/L) + PTX5 mg/L + U50488H (1 µmol/L) group. The hypertrophic myocytes were induced by Ang II 1µmol/L before κ-OR agonist U50488H 1 µmol/L was administered. The antihypertrophic effect of κ-OR stimulation was observed in the presence of ciclosporine A (CsA) 1 µmol/L, cAMP triethyl-ammonium salt (Rp-cAMPS) 1 µmol/L, and pertussistoxin ( PTX) 5 mg/L. The total protein content was assayed by the method of Lowry. The [Ca&sup2;⁺]i was measured by confocal microscope using Fluo-3/AM as flouresecent indicator. The relative expression of CaN was determined by Western blot.

RESULTS(1) The total protein content of Ang II group was significantly higher than that in control group (P<0.01), which could be equally reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). Total protein content of the Ang II + PTX + U50488H group and the Ang II group was similar. (2) The [Ca&sup2;⁺]i was significantly higher in Ang II group of neonatal rat cardiomyocytes than that in control group (P<0.01), which could be reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). [Ca(2+)]i was similar between the Ang II + PTX + U50488H group and the Ang II group. (3) The expression of CaN was significantly higher in Ang II group than that in control group (P<0.01), which could be significantly reduced by cotreatment with U50488H, CSA and Rp-cAMPS (P<0.01). CaN was similar between the Ang II + PTX + U50488H group and the Ang II group.

CONCLUSIONκ-opioid receptor activation could attenuate Ang II induced cardiomyocytes hypertrophy via reducing [Ca&sup2;⁺]i and downreglating CaN.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; Angiotensin II ; Aniline Compounds ; Animals ; Animals, Newborn ; Calcineurin ; Cells, Cultured ; Hypertrophy ; Myocardium ; Myocytes, Cardiac ; Rats ; Receptors, Opioid, kappa ; Signal Transduction ; Xanthenes

AIMIn order to study the effects of kappa-opioid receptor activation, we used cultured cardiomyocytes to study the inhibitory effects of U50,488H on cellular proliferation, protein content in the presence or absence of nor-binaltorphimine (nor-BNI).

METHODSThe cellular proliferation was determined with crystal violet staining and the protein content was assayed with Lowry's method.

RESULTSA kappa-opioid receptor agonist U50,488H at 0.1 micromol/L-10 micromol/L inhibited the cellular proliferation and protein content of cultured myocardial cells in a dose-dependent manner. The inhibitory effects of U50,488H were completely blocked by pretreatment with nor-BNI, a specific kappa-opioid receptor antagonist at 1 micromol/L.

CONCLUSIONU50,488H inhibited the cultured myocardial cells' growth. The inhibitory effects of U50,488H are involved in mediating the action of kappa-opioid receptor stimulation.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; pharmacology ; Animals ; Cell Growth Processes ; Cells, Cultured ; Myocytes, Cardiac ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, kappa ; metabolism

BACKGROUND: Because the kappa-opioid receptor (OR) agonist U50488H stimulates opioidergic regulation and inhibits L-type Ca2+ channels, this study was aimed at assessing the roles of OR and L-type Ca2+ channels on U50488H-induced cardioprotection. METHODS: Langendorff-perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Isolated hearts were treated with U50488H with or without the kappa-OR antagonist nor-binaltorphimine (nor-BNI) or the Ca2+ channels activator BAY K 8644. Infarct size was measured with 2,3,5-triphenyltetrazolium chloride staining. RESULTS: U50488H treatment at reperfusion: (1) significantly reduced infarct size (11.3 +/- 1.3%) compared to control hearts (27.7 +/- 1.1%, P < 0.001), an effect that was completely blocked by nor-BNI (24.0 +/- 0.9%, P < 0.001 vs. U50488H) but not by BAY K 8644 (7.1 +/- 1.7%, P > 0.05 vs. U50488H); (2) significantly increased left ventricular developed pressure (65.3 +/- 4.8%) after 2 h of reperfusion compared to control hearts (44.8 +/- 3.6%, P < 0.05), an effect that was abrogated by nor-BNI (40.5 +/- 4.5%, P > 0.05 vs. control) but not by BAY K 8644 (64.3 +/- 5.6%, P < 0.01 vs. control); and (3) significantly decreased heart rate (P < 0.01 vs. control), an effect that was completely abrogated by both nor-BNI and BAY K 8644. CONCLUSIONS: U50488H significantly limits myocardial infarction and stunning in isolated rat hearts after ischemia-reperfusion induction. The infarct size limitation and contractility improvement observed with U50488H treatment during reperfusion are entirely mediated by OR stimulation and not by Ca2+ channel modulation.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Animals ; Calcium ; Coronary Occlusion ; Heart ; Heart Rate ; Ischemia ; Myocardial Infarction ; Naltrexone ; Rats ; Receptors, Opioid ; Reperfusion ; Tetrazolium Salts

BACKGROUND: Because the kappa-opioid receptor (OR) agonist U50488H stimulates opioidergic regulation and inhibits L-type Ca2+ channels, this study was aimed at assessing the roles of OR and L-type Ca2+ channels on U50488H-induced cardioprotection. METHODS: Langendorff-perfused rat hearts were subjected to 30 min of regional ischemia and 2 h of reperfusion. Isolated hearts were treated with U50488H with or without the kappa-OR antagonist nor-binaltorphimine (nor-BNI) or the Ca2+ channels activator BAY K 8644. Infarct size was measured with 2,3,5-triphenyltetrazolium chloride staining. RESULTS: U50488H treatment at reperfusion: (1) significantly reduced infarct size (11.3 +/- 1.3%) compared to control hearts (27.7 +/- 1.1%, P < 0.001), an effect that was completely blocked by nor-BNI (24.0 +/- 0.9%, P < 0.001 vs. U50488H) but not by BAY K 8644 (7.1 +/- 1.7%, P > 0.05 vs. U50488H); (2) significantly increased left ventricular developed pressure (65.3 +/- 4.8%) after 2 h of reperfusion compared to control hearts (44.8 +/- 3.6%, P < 0.05), an effect that was abrogated by nor-BNI (40.5 +/- 4.5%, P > 0.05 vs. control) but not by BAY K 8644 (64.3 +/- 5.6%, P < 0.01 vs. control); and (3) significantly decreased heart rate (P < 0.01 vs. control), an effect that was completely abrogated by both nor-BNI and BAY K 8644. CONCLUSIONS: U50488H significantly limits myocardial infarction and stunning in isolated rat hearts after ischemia-reperfusion induction. The infarct size limitation and contractility improvement observed with U50488H treatment during reperfusion are entirely mediated by OR stimulation and not by Ca2+ channel modulation.
3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer ; 3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester ; Animals ; Calcium ; Coronary Occlusion ; Heart ; Heart Rate ; Ischemia ; Myocardial Infarction ; Naltrexone ; Rats ; Receptors, Opioid ; Reperfusion ; Tetrazolium Salts