u-50488 and Disease-Models--Animal

Kappa opioid receptor (KOR) agonists have anticonvulsant effect but their antiepileptogenic effect is unknown. U50488, a selective KOR agonist is used to determine its effect on status epilepticus (SE), spontaneous convulsive seizures (SS) and cognitive impairment in rat lithium-pilocarpine SE model. Effect of an antiepileptic drug levetiracetam is also studied.. Male Wistar rats with SE were divided into three groups namely, LiP, LiP + U50488 (10 mg/kg, i.p.) and LiP + levetiracetam (400 mg/kg, i.p.) group. SE was terminated after 90 min of its onset with diazepam (15 mg/kg, i.p.) and phenobarbitone (25 mg/kg, i.p.). Drug treatment was started after 15 min of onset of SE and repeated once after 4 h. Rats were video monitored 12 h daily (9 AM to 9 PM) to determine severity of SE using modified Racine scale and onset and frequency of SS from day 0 to day 21. Morris water maze (MWM) test was done at baseline i.e. day -1 (before lithium administration) and day 22, to assess cognitive impairment.. As compared to LiP, U50488 decreased the severity of SE (1.98 ± 0.13 vs 2.95 ± 0.12; p-value < 0.0001) but not levetiracetam (2.62 ± 0.09; p-value = 0.3112). Survival increased with both U50488 (90%, n = 10) and levetiracetam (81.8%, n = 11) as compared to NS (56.2%, n = 16). No effect on onset and frequency of SS was found in U50488/levetiracetam group. U50488 improved seizures-induced cognitive impairment. Levetiracetam group showed thigmotactic (wall hugging) behaviour in MWM in 8 out of 9 rats.. Acute treatment with U50488, a kappa opioid receptor agonist has a beneficial effect on SE, SE-related mortality and memory impairment. The dual protective effect of U50488 on seizures and related cognitive impairment is advantageous over currently used antiseizure drugs which are known to cause cognitive impairment.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anticonvulsants; Disease Models, Animal; Levetiracetam; Lithium; Male; Pilocarpine; Rats; Rats, Wistar; Receptors, Opioid, kappa; Seizures; Status Epilepticus

The role of opioid kappa1 and kappa2 receptors in reperfusion cardiac injury was studied. Male Wistar rats were subjected to a 45-min coronary artery occlusion followed by a 120-min reperfusion. Opioid kappa receptor agonists were administered intravenously 5 min before the onset of reperfusion, while opioid receptor antagonists were given 10 min before reperfusion. The average value of the infarct size/area at risk (IS/AAR) ratio was 43 - 48% in untreated rats. Administration of the opioid kappa1 receptor agonist (-)-U-50,488 (1 mg/kg) limited the IS/AAR ratio by 42%. Administration of the opioid kappa receptor agonist ICI 199,441 (0.1 mg/kg) limited the IS/AAR ratio by 41%. The non-selective opioid kappa receptor agonist (+)-U-50,488 (1 mg/kg) with low affinity for opioid kappa receptor, the peripherally acting opioid kappa2 receptor agonist ICI 204,448 (4 mg/kg) and the selective opioid ?2 receptor agonist GR89696 (0.1 mg/kg) had no effect on the IS/AAR ratio. Pretreatment with naltrexone, the peripherally acting opioid receptor antagonist naloxone methiodide, or the selective opioid kappa2 receptor antagonist nor-binaltorphimine completely abolished the infarct-reducing effect of (-)-U-50,488 and ICI 199,441. Pretreatment with the selective opioid ? receptor antagonist TIPP[psi] and the selective opioid µ receptor antagonist CTAP did not alter the infarct reducing effect of (-)-U-50,488 and ICI 199,441. Our study is the first to demonstrate the following: (a) the activation of opioid kappa2 receptor has no effect on cardiac tolerance to reperfusion; (b) peripheral opioid kappa1 receptor stimulation prevents reperfusion cardiac injury; (c) ICI 199,441 administration resulted in an infarct-reducing effect at reperfusion; (e) bradycardia induced by opioid kappa receptor antagonists is not dependent on the occupancy of opioid kappa receptor.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Administration, Intravenous; Analgesics, Opioid; Animals; Arrhythmias, Cardiac; Disease Models, Animal; Heart Rate; Male; Myocardial Infarction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Narcotic Antagonists; Piperazines; Pyrrolidines; Rats, Wistar; Receptors, Opioid, kappa; Signal Transduction

When Zika virus emerged as a public health emergency there were no drugs or vaccines approved for its prevention or treatment. We used a high-throughput screen for Zika virus protease inhibitors to identify several inhibitors of Zika virus infection. We expressed the NS2B-NS3 Zika virus protease and conducted a biochemical screen for small-molecule inhibitors. A quantitative structure-activity relationship model was employed to virtually screen ∼138,000 compounds, which increased the identification of active compounds, while decreasing screening time and resources. Candidate inhibitors were validated in several viral infection assays. Small molecules with favorable clinical profiles, especially the five-lipoxygenase-activating protein inhibitor, MK-591, inhibited the Zika virus protease and infection in neural stem cells. Members of the tetracycline family of antibiotics were more potent inhibitors of Zika virus infection than the protease, suggesting they may have multiple mechanisms of action. The most potent tetracycline, methacycline, reduced the amount of Zika virus present in the brain and the severity of Zika virus-induced motor deficits in an immunocompetent mouse model. As Food and Drug Administration-approved drugs, the tetracyclines could be quickly translated to the clinic. The compounds identified through our screening paradigm have the potential to be used as prophylactics for patients traveling to endemic regions or for the treatment of the neurological complications of Zika virus infection.

Topics: Animals; Antiviral Agents; Artificial Intelligence; Chlorocebus aethiops; Disease Models, Animal; Drug Evaluation, Preclinical; High-Throughput Screening Assays; Immunocompetence; Inhibitory Concentration 50; Methacycline; Mice, Inbred C57BL; Protease Inhibitors; Quantitative Structure-Activity Relationship; Small Molecule Libraries; Vero Cells; Zika Virus; Zika Virus Infection

κ-opioid receptor (κ-OR) plays a key role in preventing hypoxic pulmonary hypertension (HPH) development after activated by exogenous agonist U50,488H. Calcium sensing receptor (CaSR) activation induces HPH by promoting vasoconstriction and vascular remodeling. The activated κ-OR is reported to inhibit the expression of CaSR in pulmonary artery smooth muscle cells (PASMCs). Thus, in this study, we aimed to explore the effect of activated κ-OR on the role of CaSR in preventing HPH development. An HPH rat model was constructed using Sprague-Dawley rats. Changes in mean pulmonary arterial pressure (mPAP) and right ventricular pressure (RVP) mediated by κ-OR agonist U50,488H and CaSR inhibitor NPS2143 were observed. The effects of CaSR agonist spermine and inhibitor NPS2143 on pulmonary artery tension were tested. The expression and localization of κ-OR and CaSR were measured in isolated PASMCs. A cell-counting kit-8 assay was performed to evaluate the effect of spermine in PASMC proliferation. Expression of proliferating cell nuclear antigen (PCNA), Erk, and p-Erk was evaluated by western blot analysis. Results showed that κ-OR and CaSR were co-expressed and colocalized in PASMCs under normoxic and hypoxic conditions. Interactions between κ-OR and CaSR were also observed. Spermine improved vasoconstriction in the pulmonary artery in HPH rats, which was abolished by U50,488H. RVP and mPAP were significantly increased in HPH rats under CaSR stimulation, but were significantly reduced when the rats were pretreated with U50,488H and NPS2143 (P < 0.01). Spermine treatment significantly promoted PASMC proliferation, which was significantly inhibited by U50,488H, p38 inhibitor SB203580, JNK inhibitor SP600125, Erk inhibitor SCH772984, and MEK inhibitor U0126, especially Erk inhibitor (P < 0.01). Spermine significantly increased PCNA and P-Erk expression in hypoxic conditions, which was inhibited by U50,488H and NPS2143. κ-OR stimulation prevented HPH development via the CaSR/MAPK signaling pathway.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Cell Proliferation; Disease Models, Animal; Hypertension, Pulmonary; Hypoxia; Male; MAP Kinase Signaling System; Myocytes, Smooth Muscle; Naphthalenes; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Calcium-Sensing; Receptors, Opioid, kappa; Signal Transduction; Spermine; Vascular Remodeling

KOP-r agonist U50,488H produces strong aversion and anxiety/depression-like behaviors that enhance alcohol intake and promote alcohol seeking and relapse-like drinking in rodents. Mammalian target of rapamycin complex 1 (mTORC1) pathway in mouse striatum is highly involved in excessive alcohol intake and seeking, and in the U50,488H-induced conditioned place aversion. Therefore, we hypothesized that KOP-r activation increases alcohol consumption through the mTORC1 activation. This study focuses on: (1) how chronic excessive alcohol drinking (4-day drinking-in-the-dark paradigm followed by 3-week chronic intermittent access drinking paradigm [two-bottle choice, 24-h access every other day]) affected nuclear transcript levels of the mTORC1 pathway genes in mouse nucleus accumbens shell (NAcs), using transcriptome-wide RNA sequencing analysis; and (2) whether selective mTORC1 inhibitor rapamycin could alter excessive alcohol drinking and prevent U50,488H-promoted alcohol intake. Thirteen nuclear transcripts of mTORC1 pathway genes showed significant up-regulation in the NAcs, with two genes down-regulated, after excessive alcohol drinking, suggesting the mTORC1 pathway was profoundly disrupted. Single administration of rapamycin decreased alcohol drinking in a dose-dependent manner. U50,488H increased alcohol drinking, and pretreatment with rapamycin, at a dose lower than effective doses, blocked the U50,488H-promoted alcohol intake in a dose-dependent manner, indicating a mTORC1-mediated mechanism. Our results provide supportive and direct evidence relevant to the transcriptional profiling of the critical mTORC1 genes in mouse NAc shell: with functional and pharmacological effects of rapamycin, altered nuclear transcripts in the mTORC1 signaling pathway after excessive alcohol drinking may contribute to increased alcohol intake triggered by KOP-r activation.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Binge Drinking; Central Nervous System Depressants; Disease Models, Animal; Ethanol; Gene Expression; Male; Mechanistic Target of Rapamycin Complex 1; Mice; Mice, Inbred C57BL; Nucleus Accumbens; Receptors, Opioid, kappa; Signal Transduction; Sirolimus; Transcriptome

Patients with cholestatic liver diseases, such as primary biliary cirrhosis, usually suffer from pruritus. However, the pathogenesis of cholestatic pruritus is unclear, and there is no current effective treatment for it. In order to find a treatment for the condition, an appropriate mouse model should be developed. Therefore, here, we established a surgically-induced mouse model of cholestatic pruritus. The bile duct was ligated in order to block bile secretion from the anterior, right, and left lobes, with the exception of the caudate lobe. Serum levels of total bile acid increased after bile duct ligation (BDL). The spontaneous hind paw scratching was also increased in BDL mice. Spontaneous scratching was reduced in BDL mice by naloxone (µ-opioid receptor antagonist), U-50,488H (κ-opioid receptor agonist), and clonidine (α2-adrenoceptor agonist). Azelastine (H

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenergic alpha-2 Receptor Agonists; Animals; Antipruritics; Bile Ducts; Cholestasis; Clonidine; Disease Models, Animal; Ligation; Liver; Male; Mice, Inbred ICR; Naloxone; Narcotic Antagonists; Pruritus; Receptors, Opioid, kappa

Stress is associated with relapse to alcohol seeking during abstinence, but the processes underlying this relationship are poorly understood. Noradrenaline is a key transmitter in stress responses and in stress-induced drug seeking. The alpha-1 adrenoceptor antagonist prazosin has been investigated as a treatment for alcoholism and for chronic stress disorders that are frequently comorbid with alcoholism. In rats, we previously showed that prazosin blocks reinstatement of alcohol seeking induced by footshock and yohimbine stressors and reduces yohimbine-induced brain activation. The role of alpha-1 adrenoceptors in reinstatement induced by other stressors is not known. Our most recent work is on the role of kappa opioid receptors in stress-induced reinstatement of alcohol seeking and have reported that the selective kappa opioid receptor agonist U50,488 induces reinstatement and neuronal activation in stress- and relapse-related brain regions. Here we determine the involvement of alpha-1 receptors in reinstatement and brain activation induced by U50,488.. We trained male Long-Evans rats to self-administer alcohol (12% w/v), extinguished alcohol-reinforced responding, and then determined the effects of prazosin (1 mg/kg) on U50,488 (2.5 mg/kg)-induced reinstatement and regional Fos expression.. Prazosin blocked U50,488-induced reinstatement and decreased U50,488-induced Fos expression in the orbitofrontal cortex, nucleus accumbens core, ventral bed nucleus of the stria terminalis, central and basolateral amygdalar nuclei and ventral tegmental area.. These findings suggest that prazosin may reduce U50,488-induced relapse by inhibiting activity in 1 or more of these brain areas.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenergic alpha-1 Receptor Antagonists; Alcoholism; Animals; Behavior, Animal; Brain; Central Nervous System Depressants; Disease Models, Animal; Ethanol; Gene Expression; Genes, fos; Male; Prazosin; Rats; Rats, Long-Evans; Receptors, Opioid, kappa; Stress, Psychological

Kappa opioid receptor (KOR) agonists produce analgesic and anti-pruritic effects, but their clinical application was limited by dysphoria and hallucinations. Nalfurafine, a clinically used KOR agonist, does not cause dysphoria or hallucinations at therapeutic doses in humans. We found that in CD-1 mice nalfurafine produced analgesic and anti-scratch effects dose-dependently, like the prototypic KOR agonist U50,488H. In contrast, unlike U50,488H, nalfurafine caused no aversion, anhedonia, or sedation or and a low level of motor incoordination at the effective analgesia and anti-scratch doses. Thus, we established a mouse model that recapitulated important aspects of the clinical observations. We then employed a phosphoproteomics approach to investigate mechanisms underlying differential KOR-mediated effects. A large-scale mass spectrometry (MS)-based analysis on brains revealed that nalfurafine perturbed phosphoproteomes differently from U50,488H in a brain-region specific manner after 30-min treatment. In particular, U50,488H and nalfurafine imparted phosphorylation changes to proteins found in different cellular components or signaling pathways in different brain regions. Notably, we observed that U50,488H, but not nalfurafine, activated the mammalian target of rapamycin (mTOR) pathway in the striatum and cortex. Inhibition of the mTOR pathway by rapamycin abolished U50,488H-induced aversion, without affecting analgesic, anti-scratch, and sedative effects and motor incoordination. The results indicate that the mTOR pathway is involved in KOR agonist-induced aversion. This is the first demonstration that phosphoproteomics can be applied to agonist-specific signaling of G protein-coupled receptors (GPCRs) in mouse brains to unravel pharmacologically important pathways. Furthermore, this is one of the first two reports that the mTOR pathway mediates aversion caused by KOR activation.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Antipruritics; Behavior, Animal; Brain; Disease Models, Animal; Male; Mass Spectrometry; Mice; Mice, Inbred C57BL; Mice, Knockout; Morphinans; Nociception; Phosphorylation; Proteomics; Receptors, Opioid, kappa; Signal Transduction; Spiro Compounds; TOR Serine-Threonine Kinases

Previous studies have shown that κ-opioid receptor activation possesses cardioprotection against myocardial ischemia and reperfusion (MI/R) injury. The current study was designed to investigate whether mitochondrial dysfunction after MI/R is regulated by the κ-opioid receptor and to further explore the underlying mechanisms involved. MI/R rat model was established in vivo, and a hypoxia and reoxygenation cardiomyocytes model was used in vitro. Mitochondrial morphology and function as well as myocardial apoptosis were determined. Our data indicated that treatment with U50,488H (a selective κ-opioid receptor agonist) not only reduced apoptosis but also significantly improved mitochondrial morphology and function. These effects were blocked by nor-binaltorphimine (nor-BNI, a selective κ-opioid receptor antagonist), Compound C (an AMPK inhibitor), and AR-A014418 (a GSK3β inhibitor). Moreover, in cardiomyocytes, treatment with U50,488H significantly increased the expression in phosphorylation of AMPK and the phosphorylation of GSK3β. Treatment of cardiomyocytes with AMPKα siRNA decreased the phosphorylation of AMPK and GSK3β. Moreover, AMPK activation resulted in the phosphorylation of GSK3β. Our findings suggested that U50,488H exerted cardioprotective effects by improving mitochondrial morphology and function against MI/R injury through activation of the κ-opioid receptor-mediated AMPK/GSK3β pathway.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; AMP-Activated Protein Kinases; Animals; Apoptosis; Cell Line; Disease Models, Animal; Glycogen Synthase Kinase 3 beta; Male; Mitochondria, Heart; Myocardial Infarction; Myocardial Reperfusion Injury; Myocytes, Cardiac; Phosphorylation; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Signal Transduction

Although previous research has demonstrated a role for kappa opioid receptor-mediated signaling in escalated alcohol consumption associated with dependence and stress exposure, involvement of the dynorphin/kappa opioid receptor (DYN/KOR) system in binge-like drinking has not been fully explored. Here we used pharmacological and chemogenetic approaches to examine the influence of DYN/KOR signaling on alcohol consumption in the drinking-in-the-dark (DID) model of binge-like drinking. Systemic administration of the KOR agonist U50,488 increased binge-like drinking (Experiment 1) while, conversely, systemic administration of the KOR antagonist nor-BNI reduced drinking in the DID model (Experiment 2). These effects of systemic KOR manipulation were selective for alcohol as neither drug influenced consumption of sucrose in the DID paradigm (Experiment 3). In Experiment 4, administration of the long-acting KOR antagonist nor-BNI into the central nucleus of the amygdala (CeA) decreased alcohol intake. Next, targeted "silencing" of DYN+ neurons in the CeA was accomplished using a chemogenetic strategy. Cre-dependent viral expression in DYN+ neurons was confirmed in CeA of Pdyn-IRES-Cre mice and functionality of an inhibitory (hM4Di) DREADD was validated (Experiment 5). Activating the inhibitory DREADD by CNO injection reduced binge-like alcohol drinking, but CNO injection did not alter alcohol intake in mice that were treated with control virus (Experiment 6). Collectively, these results demonstrate that DYN/KOR signaling in the CeA contributes to excessive alcohol consumption in a binge-drinking model.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Behavior, Animal; Binge Drinking; Central Amygdaloid Nucleus; Disease Models, Animal; Dynorphins; Genetic Techniques; Male; Mice; Mice, Inbred C57BL; Naltrexone; Receptors, Opioid, kappa

Breast cancer metastasizes to bone, diminishing quality of life of patients because of pain, fracture, and limited mobility. Cancer-induced bone pain (CIBP) is characterized as moderate to severe ongoing pain, primarily managed by mu opioid agonists such as fentanyl. However, opioids are limited by escalating doses and serious side effects. One alternative may be kappa opioid receptor (KOR) agonists. There are few studies examining KOR efficacy on CIBP, whereas KOR agonists are efficacious in peripheral and inflammatory pain. We thus examined the effects of the KOR agonist U50,488 given twice daily across 7 days to block CIBP, tumor-induced bone loss, and tumor burden. U50,488 dose-dependently blocked tumor-induced spontaneous flinching and impaired limb use, without changing tactile hypersensitivity, and was fully reversed by the KOR antagonist nor-binaltorphimine. U50,488 treatment was higher in efficacy and duration of action at later time points. U50,488 blocked this pain without altering tumor-induced bone loss or tumor growth. Follow-up studies in human cancer cell lines confirmed that KOR agonists do not affect cancer cell proliferation. These studies suggest that KOR agonists could be a new target for cancer pain management that does not induce cancer cell proliferation or alter bone loss.. This study demonstrates the efficacy of KOR agonists in the treatment of bone cancer-induced pain in mice, without changing tumor size or proliferation in cancer cell lines. This suggests that KOR agonists could be used to manage cancer pain without the drawbacks of mu opioid agonists and without worsening disease progression.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Bone and Bones; Cancer Pain; Cell Proliferation; Disease Models, Animal; Female; Mice; Receptors, Opioid, kappa

A series of twenty two (E)-N-cinnamoyl aminoalkanols derivatives monosubstituted in phenyl ring with 4-Cl, 4-CH

Topics: Amino Alcohols; Animals; Anticonvulsants; Crystallography, X-Ray; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Mice; Models, Molecular; Molecular Structure; Rats; Seizures; Structure-Activity Relationship

In a previous study, we showed that κ-opioid receptor stimulation with the selective agonist U50,488H ameliorated hypoxic pulmonary hypertension (HPH). However, the roles that pulmonary arterial smooth muscle cell (PASMC) proliferation, apoptosis, and autophagy play in κ-opioid receptor-mediated protection against HPH are still unknown. The goal of the present study was to investigate the role of autophagy in U50,488H-induced HPH protection and the underlying mechanisms.. Rats were exposed to 10% oxygen for three weeks to induce HPH. After hypoxia, the mean pulmonary arterial pressure (mPAP) and the right ventricular pressure (RVP) were measured. Cell viability was monitored using the Cell Counting Kit-8 (CCK-8) assay. Cell apoptosis was detected by flow cytometry and Western blot. Autophagy was assessed by means of the mRFP-GFP-LC3 adenovirus transfection assay and by Western blot.. Inhibition of autophagy by the administration of chloroquine prevented the development of HPH in the rat model, as evidenced by significantly reduced mPAP and RVP, as well as decreased autophagy. U50,488H mimicked the effects of chloroquine, and the effects of U50,488H were blocked by nor-BNI, a selective κ-opioid receptor antagonist. In vitro experiments showed that the inhibition of autophagy by chloroquine was associated with decreased proliferation and increased apoptosis of PASMCs. Under hypoxia, U50,488H also significantly inhibited autophagy, reduced proliferation and increased apoptosis of PASMCs. These effects of U50,488H were blocked by nor-BNI. Moreover, exposure to hypoxic conditions significantly increased AMPK phosphorylation and reduced mTOR phosphorylation, and these effects were abrogated by U50,488H. The effects of U50,488H on PASMC autophagy were inhibited by AICAR, a selective AMPK agonist, or by rapamycin, a selective mTOR inhibitor.. Our data provide evidence for the first time that κ-opioid receptor stimulation protects against HPH by inhibiting PASMCs autophagy via the AMPK-mTOR pathway.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; AMP-Activated Protein Kinases; Animals; Antihypertensive Agents; Apoptosis; Autophagy; Blood Pressure; Cell Proliferation; Cells, Cultured; Chloroquine; Disease Models, Animal; Hypertension, Pulmonary; Male; Myocytes, Smooth Muscle; Naltrexone; Pulmonary Artery; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Signal Transduction; TOR Serine-Threonine Kinases

Dynorphin 1-17 is an endogenous peptide that is released at sites of inflammation by leukocytes, binding preferentially to κ-opioid receptors (KOP) to mediate nociception. We have previously shown that dynorphin 1-17 is rapidly biotransformed to smaller peptide fragments in inflamed tissue homogenate. This study aimed to determine the efficacy and potency of selected dynorphin fragments produced in an inflamed environment at the KOP, μ and δ-opioid receptors (MOP and DOP respectively) and in a model of inflammatory pain. Functional activity of Dynorphin 1-17 and fragments (1-6, 1-7 and 1-9) were screened over a range of concentrations against forskolin stimulated human embryonic kidney 293 (HEK) cells stably transfected with one of KOP, MOP or DOP. The analgesic activity of dynorphin 1-7 in a unilateral model of inflammatory pain was subsequently tested. Rats received unilateral intraplantar injections of Freund's Complete Adjuvant to induce inflammation. After six days rats received either dynorphin 1-7, 1-17 or the selective KOP agonist U50488H and mechanical allodynia determined. Dynorphin 1-7 and 1-9 displayed the greatest activity across all receptor subtypes, while dynorphin 1-7, 1-9 and 1-17 displaying a potent activation of both KOP and DOP evidenced by cAMP inihibition. Administration of dynorphin 1-7 and U50488H, but not dynorphin 1-17 resulted in a significant increase in paw pressure threshold at an equimolar dose suggesting the small peptide dynorphin 1-7 mediates analgesia. These results show that dynorphin fragments produced in an inflamed tissue homogenate have changed activity at the opioid receptors and that dynorphin 1-7 mediates analgesia.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Animals; Disease Models, Animal; Dynorphins; HEK293 Cells; Humans; Inflammation; Pain; Rats; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Transfection

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional disorder of the gastrointestinal (GI) tract. The major IBS-D symptoms include diarrhea, abdominal pain and discomfort. High density of opioid receptors (ORs) in the GI tract and their participation in the maintenance of GI homeostasis make ORs ligands an attractive option for developing new anti-IBS-D treatments. The aim of this study was to characterize the effect of methyl-orvinol on the GI motility and secretion and in mouse models mimicking symptoms of IBS-D.. In vitro, the effects of methyl-orvinol on electrical field stimulated smooth muscle contractility and epithelial ion transport were characterized in the mouse colon. In vivo, the following tests were used to determine methyl-orvinol effect on mouse GI motility: colonic bead expulsion, whole GI transit and fecal pellet output. An antinociceptive action of methyl-orvinol was assessed in the mouse model of visceral pain induced by mustard oil.. Methyl-orvinol (10. Methyl-orvinol could become a promising drug candidate in chronic therapy of functional GI diseases such as IBS-D.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Abdominal Pain; Analgesics; Analgesics, Opioid; Animals; Colon; Diarrhea; Disease Models, Animal; Gastrointestinal Motility; Gastrointestinal Transit; Irritable Bowel Syndrome; Male; Mice; Mice, Inbred BALB C; Muscle Contraction; Muscle, Smooth; Naloxone; Naltrexone; Receptors, Opioid; Thebaine

Selective activation of peripheral κ opioid receptors (KORs) may overcome the dose-limiting adverse effects of conventional opioid analgesics. We recently developed a vicinal disulfide-stabilized class of peptides with subnanomolar potency at the KOR. The aim of this study was to assess the analgesic effects of one of these peptides, named conorphin-1, in comparison with the prototypical KOR-selective small molecule agonist U-50488, in several rodent pain models. Surprisingly, neither conorphin-1 nor U-50488 were analgesic when delivered peripherally by intraplantar injection at local concentrations expected to fully activate the KOR at cutaneous nerve endings. While U-50488 was analgesic when delivered at high local concentrations, this effect could not be reversed by coadministration with the selective KOR antagonist ML190 or the nonselective opioid antagonist naloxone. Instead, U-50488 likely mediated its peripheral analgesic effect through nonselective inhibition of voltage-gated sodium channels, including peripheral sensory neuron isoforms NaV1.8 and NaV1.7. Our study suggests that targeting the KOR in peripheral sensory nerve endings innervating the skin is not an alternative analgesic approach.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Non-Narcotic; Animals; Carrageenan; Cisplatin; Disease Models, Animal; Freund's Adjuvant; Gene Expression Regulation; HEK293 Cells; Humans; Inflammation; Male; Mice; Mice, Inbred C57BL; Naloxone; Nerve Endings; Oligopeptides; Pain; Pain Measurement; Peptides; Peripheral Nervous System Diseases; Rats; Rats, Wistar; Receptors, Opioid, kappa; Skin

The kappa opioid receptor (KOR) is involved in mediating pruritus; agonists targeting this receptor have been used to treat chronic intractable itch. Conversely, antagonists induce an itch response at the site of injection. As a G protein-coupled receptor (GPCR), the KOR has potential for signaling via G proteins and βarrestins, however, it is not clear which of these pathways are involved in the KOR modulation of itch. In this study asked whether the actions of KOR in pruritus involve βarrestins by using βarrestin2 knockout (βarr2-KO) mice as well as a recently described biased KOR agonist that biases receptor signaling toward G protein pathways over βarrestin2 recruitment. We find that the KOR antagonists nor-binaltorphimine (NorBNI) and 5'-guanidinonaltrindole (5'GNTI) induce acute pruritus in C57BL/6J mice, with reduced effects in KOR-KO mice. βArr2-KO mice display less of a response to KOR antagonist-induced itch compared to wild types, however no genotype differences are observed from chloroquine phosphate (CP)-induced itch, suggesting that the antagonists may utilize a KOR-βarrestin2 dependent mechanism. The KOR agonist U50,488H was equally effective in both WT and βarr2-KO mice in suppressing CP-induced itch. Furthermore, the G protein biased agonist, Isoquinolinone 2.1 was as effective as U50,488H in suppressing the itch response induced by KOR antagonist NorBNI or CP in C57BL/6J mice. Together these data suggest that the antipruritic effects of KOR agonists may not require βarrestins.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Opioid; Animals; Arrestins; beta-Arrestins; Chloroquine; Disease Models, Animal; Dose-Response Relationship, Drug; Guanidines; Isoquinolines; Male; Mice, Inbred C57BL; Mice, Knockout; Morphinans; Motor Activity; Naltrexone; Pruritus; Receptors, Opioid, kappa

Carrageenan-induced hyperalgesia is a widely used pain model in rodents. However, characteristics of carrageenan-induced hyperalgesia and effects of analgesic drugs under these conditions are unknown in nonhuman primates.. The aims of this study were to develop carrageenan-induced hyperalgesia in rhesus monkeys and determine the efficacy and potency of agonists selective for the four opioid receptor subtypes in this model versus acute pain, as compared to non-steroidal anti-inflammatory drugs (NSAIDs).. Tail injection of carrageenan produced long-lasting thermal hyperalgesia in monkeys. Systemically administered agonists selective for opioid receptor subtypes, i.e., fentanyl (mu/MOP), U-50488H (kappa/KOP), SNC80 (delta/DOP) and Ro 64-6198 (nociceptin/orphanin FQ/NOP) dose-dependently attenuated carrageenan-induced thermal hyperalgesia with different potencies. In absence of carrageenan, these agonists, except SNC80, blocked acute thermal nociception. Opioid-related ligands, especially Ro 64-6198, were much more potent for their antihyperalgesic than antinociceptive effects. Both effects were mediated by the corresponding receptor mechanisms. Only fentanyl produced scratching at antihyperalgesic and antinociceptive doses consistent with its pruritic effects in humans, illustrating a translational profile of MOP agonists in nonhuman primates. Similar to SNC80, systemically administered NSAIDs ketorolac and naproxen dose-dependently attenuated carrageenan-induced hyperalgesia but not acute nociception.. Using two different pain modalities in nonhuman primates, effectiveness of clinically available analgesics like fentanyl, ketorolac and naproxen was distinguished and their efficacies and potencies were compared with the selective KOP, DOP, and NOP agonists. The opioid-related ligands displayed differential pharmacological properties in regulating hyperalgesia and acute nociception in the same subjects. Such preclinical primate models can be used to investigate novel analgesic agents.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Acute Pain; Analgesics, Opioid; Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzamides; Carrageenan; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Fentanyl; Hyperalgesia; Imidazoles; Inflammation; Macaca; Male; Nociceptive Pain; Pain Measurement; Piperazines; Receptors, Opioid; Spiro Compounds

Despite many advances, our understanding of the involvement of prodynorphin systems in the development of neuropathic pain is not fully understood. Recent studies suggest an important role of neuro-glial interactions in the dynorphin effects associated with neuropathic pain conditions. Our studies show that minocycline reduced prodynorphin mRNA levels that were previously elevated in the spinal and/or dorsal root ganglia (DRG) following sciatic nerve injury. The repeated intrathecal administration of minocycline enhanced the analgesic effects of low-dose dynorphin (0.15 nmol) and U50,488H (25-100 nmol) and prevented the development of flaccid paralysis following high-dose dynorphin administration (15 nmol), suggesting a neuroprotective effect. Minocycline reverts the expression of IL-1β and IL-6 mRNA within the spinal cord and IL-1β mRNA in DRG, which was elevated following intrathecal administration of dynorphin (15 nmol). These results suggest an important role of these proinflammatory cytokines in the development of the neurotoxic effects of dynorphin. Similar to minocycline, a selective inhibitor of MMP-9 (MMP-9 levels are reduced by minocycline) exerts an analgesic effect in behavioral studies, and its administration prevents the occurrence of flaccid paralysis caused by high-dose dynorphin administration (15 nmol). In conclusion, our results underline the importance of neuro-glial interactions as evidenced by the involvement of IL-1β and IL-6 and the minocycline effect in dynorphin-induced toxicity, which suggests that drugs that alter the prodynorphin system could be used to better control neuropathic pain.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Disease Models, Animal; Dynorphins; Ganglia, Spinal; Injections, Spinal; Interleukin-1beta; Interleukin-6; Male; Matrix Metalloproteinase 9; Minocycline; Neuralgia; Neuroprotective Agents; Paraplegia; Rats, Wistar; RNA, Messenger; Sciatic Neuropathy; Spinal Cord

The beneficial effects of kappa opioid agonist U-50,488 in preventing periodontal disease (PD) progression in rats have already been described, but its mechanism of action is unknown. The present study evaluated the expression of TNF-α, IL-6, IL-8 and IL-10 in the gingival tissues of rats with ligature-induced PD, treated with U-50,488. It also correlated the effects of this agonist with myeloperoxidase (MPO) activity and the presence of osteoclasts.. Male Holtzman rats weighing 250-300 g were divided into four groups: (1) control, (2) ligature, (3) ligature+saline and (4) ligature+kappa agonist. Experimental PD was induced by placing a sterile silk ligature around the 2nd left upper molar. Rats from groups 3 to 4 were locally administered with either saline or U-50,488, respectively, from day 3 to day 5 following ligation. After 5 or 11 days, the rats were euthanized and periodontal tissue samples were collected for histological and morphometric analysis and for determination of TNF-α, IL-6, IL-8, IL-10 and MPO.. Ligature placement induced significant alveolar bone loss. The number of osteoclasts, degree of MPO activity, IL-6, IL-8 and TNF-α expression were also increased by PD. U-50,488 reduced both bone loss and the number of osteoclasts, but did not alter histological inflammatory infiltrate or MPO activity. U-50,488 significantly reduced IL-6 and increased IL-10 levels, but did not affect TNF-α and IL-8.. Lowering the levels of IL-6 and increasing IL-10 are important mechanisms by which U-50,488 reduces alveolar bone loss in ligature-induced periodontal disease.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Alveolar Bone Loss; Analysis of Variance; Animals; Disease Models, Animal; Interleukin-10; Interleukin-6; Interleukin-8; Male; Osteoclasts; Peroxidase; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Tumor Necrosis Factor-alpha

By use of parallel chemistry coupled with physicochemical property design, a series of selective κ opioid antagonists have been discovered. The parallel chemistry strategy utilized key monomer building blocks to rapidly expand the desired SAR space. The potency and selectivity of the in vitro κ antagonism were confirmed in the tail-flick analgesia model. This model was used to build an exposure-response relationship between the κ K(i) and the free brain drug levels. This strategy identified 2-methyl-N-((2'-(pyrrolidin-1-ylsulfonyl)biphenyl-4-yl)methyl)propan-1-amine, PF-4455242, which entered phase 1 clinical testing and has demonstrated target engagement in healthy volunteers.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Area Under Curve; Biphenyl Compounds; Brain; Disease Models, Animal; Dogs; Drug Design; Drug Discovery; Haplorhini; Humans; Metabolic Clearance Rate; Mice; Microsomes, Liver; Models, Chemical; Molecular Structure; Morphine; Narcotic Antagonists; Pain; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Receptors, Opioid, mu; Structure-Activity Relationship; Sulfonamides

The role of the κ-opioid receptor in inflammation is not well understood. The aim of this study was to investigate whether the κ-opioid receptor agonist U50,488H modulates neutrophil accumulation and TNF-α induction in an ischemia-reperfusion injured rat heart model. Rats were randomly exposed to sham operation, myocardial ischemia-reperfusion (MI/R) alone, MI/R+U50,488H, MI/R+U50,488H+Wortmannin, and MI/R+U50,488H+L-NAME. The results demonstrated that compared to MI/R, U50,488H reduced myocardial infarction area, myocardial myeloperoxidase (MPO) levels, serum creatinine kinase (CK) levels, and both serum and myocardial TNF-α production. Increases were seen in NOx levels in the myocardium subjected to MI/R injury. All demonstrated effects of U50,488H were abolished by Nor-BNI, a selective κ-opioid receptor antagonist; Wortmannin, a specific PI3K inhibitor; or L-NAME, a nitric oxide synthase (NOS) inhibitor. In summary, κ-opioid receptor stimulation with U50,488H produces both cardioprotective and anti-inflammatory effects. These effects may be associated with an increase in NO production and the inhibition of neutrophil accumulation and TNF-α induction via a PI3K sensitive pathway in myocardium subjected to MI/R.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Creatine Kinase; Disease Models, Animal; Heart; Male; Myocardial Reperfusion Injury; Neutrophils; Nitric Oxide; Peroxidase; Rats; Rats, Sprague-Dawley; Tumor Necrosis Factor-alpha

Stress exposure increases the risk of addictive drug use in human and animal models of drug addiction by mechanisms that are not completely understood. Mice subjected to repeated forced swim stress (FSS) before cocaine develop significantly greater conditioned place preference (CPP) for the drug-paired chamber than unstressed mice. Analysis of the dose dependency showed that FSS increased both the maximal CPP response and sensitivity to cocaine. To determine whether FSS potentiated CPP by enhancing associative learning mechanisms, mice were conditioned with cocaine in the absence of stress, then challenged after association was complete with the kappa-opioid receptor (KOR) agonist U50,488 or repeated FSS, before preference testing. Mice challenged with U50,488 60 min before CPP preference testing expressed significantly greater cocaine-CPP than saline-challenged mice. Potentiation by U50,488 was dose and time dependent and blocked by the KOR antagonist norbinaltorphimine (norBNI). Similarly, mice subjected to repeated FSS before the final preference test expressed significantly greater cocaine-CPP than unstressed controls, and FSS-induced potentiation was blocked by norBNI. Novel object recognition (NOR) performance was not affected by U50,488 given 60 min before assay, but was impaired when given 15 min before NOR assay, suggesting that KOR activation did not potentiate CPP by facilitating memory retrieval or expression. The results from this study show that the potentiation of cocaine-CPP by KOR activation does not result from an enhancement of associative learning mechanisms and that stress may instead enhance the rewarding valence of cocaine-associated cues by a dynorphin-dependent mechanism.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analysis of Variance; Anesthetics, Local; Animals; Association Learning; Behavior, Animal; Cocaine; Conditioning, Operant; Cues; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Schedule; Drug Interactions; Dynorphins; Exploratory Behavior; Male; Mental Recall; Mice; Mice, Inbred C57BL; Naltrexone; Narcotic Antagonists; Receptors, Opioid, kappa; Reward; Stress, Psychological; Swimming

Acute myocardial ischemia induces electrical and chemical uncoupling of gap junctions, which contributes to conduction abnormalities and re-entrant arrhythmias. We tested the hypothesis that structure and function of Connexin43 may vibrate during acute myocardial ischemia and reperfusion and κ-opioid receptor stimulation may stabilize the alteration of Connexin43.. An animal intervention study was conducted with comparison to a control group.. University preclinical research laboratory.. Age-, weight-, and sex-matched Sprague-Dawley rats.. Adult rat hearts were subjected to ischemia or ischemia/reperfusion, which was induced by temporary occlusion of the left main coronary artery. U50488H was given 10 mins before tissue specimens were taken or before ischemia (1.5 mg/kg, intravenous) and nor-BNI was given 15 mins before tissue specimens were taken or before ischemia (2 mg/kg, intravenous). Tissue samples came from left ventricular myocardium of the rat hearts.. Electrocardiogram, immunohistochemistry, immunoblotting, and reverse transcription-polymerase chain reaction were used to measure changes of arrhythmias, protein, and gene expression of Connexin43, respectively. κ-opioid receptor activation with U50 decreased arrhythmia in a model of myocardial ischemia and reperfusion. In normal hearts, immunohistochemical data showed reduced amount and lateralization of Connexin43 induced by κ-opioid receptor activation, whereas immunoblotting data demonstrated no significant changes between control and U50 group. During ischemia, however, Connexin43 protein underwent dephosphorylation and degradation, and Connexin43 mRNA was upregulated. These alterations were significantly attenuated on κ-opioid receptor stimulation. During ischemia and reperfusion, Connexin43 protein underwent dephosphorylation and degradation and recovered slowly during reperfusion. Activation of κ-opioid receptor accelerated recovery of phosphorylated and total Connexin43.. In normal rat hearts, Connexin43 translocates from intercellular junctions to intracellular locations on κ-opioid receptor activation. In rat hearts experiencing acute myocardial ischemia and reperfusion, protein and gene expression of Connexin43 undergo vibration. This phenomenon is stabilized when κ-opioid receptor is activated and by the fact that κ-opioid receptor produces antiarrhythmic effects.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Arrhythmias, Cardiac; Blotting, Western; Connexin 43; Disease Models, Animal; Female; Gap Junctions; Immunohistochemistry; Male; Myocardial Ischemia; Myocardial Reperfusion Injury; Random Allocation; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Reference Values; Reverse Transcriptase Polymerase Chain Reaction

Opioids/opiates are commonly administered to alleviate pain, unload the heart, or decrease breathlessness in patients with advanced heart failure. As such, it is important to evaluate whether the myocardial opioidergic system is altered in cardiac disease. A hamster model of spontaneous hypertension was investigated before the development of hypertension (1 mo of age) and in the hypertensive state (10 mo of age) to evaluate the effect of prolonged hypertension on myocardial opioidergic activity. Plasma beta-endorphin was decreased before the development of hypertension and in the hypertensive state (P < 0.05). There was no change in cardiac beta-endorphin content at either time point. No differences were detected in cardiac or plasma dynorphin A, Met-enkephalin, or Leu-enkephalin, or in cardiac peptide expression of kappa- or delta-opioid receptors. mu-Opioid receptor was not detected in either model. To determine how hypertension affects myocardial opioid signaling, the ex vivo work-performing heart was used to assess the cardiac response to opioid administration in healthy hearts and those subjected to chronic hypertension. Agonists selective for the kappa- and delta-opioid receptors, but not mu-opioid receptors, induced a concentration-dependent decrease in cardiac function. The decrease in left ventricular systolic pressure on administration of the kappa-opioid receptor-selective agonist, U50488H, was attenuated in hearts from hamsters subjected to chronic, untreated hypertension (P < 0.05) compared with control. These results show that peripheral and myocardial opioid expression and signaling are altered in hypertension.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Antihypertensive Agents; Benzamides; beta-Endorphin; Blood Pressure; Cricetinae; Cyclic AMP; Disease Models, Animal; Dynorphins; Enkephalin, Leucine; Enkephalin, Methionine; Hypertension; Hypertrophy, Left Ventricular; Myocardial Contraction; Myocardium; Piperazines; Receptors, Opioid, delta; Receptors, Opioid, kappa; Systole; Ventricular Remodeling

The aim of the present study was to determine whether U50,488H (a selective kappa-opioid receptor agonist) inhibits cardiac hypertrophy and fibrosis induced by beta-adrenoceptor stimulation in a rat model. Cardiac hypertrophy and fibrosis were developed by intraperitoneal administration of isoprenaline (ip. 3.0 mg/kg/day,14 days). In the isoprenaline-treated group, heart weight and heart-to-body ratio increased significantly. Hypertrophic alterations were observed in light micrographs of tissue and transmission electron micrographs of myocardial ultra structures. Increases in heart weight, heart-to-body ratio, diameter of cardiomyocytes, and morphological hypertrophic alterations induced by isoprenaline were significantly attenuated by U50,488H(i.p. 1.25 mg/kg/day). Growth of cardiomyocytes was induced by incubating with isoprenaline (10(-6) mol/l), which resulted in an increase in optical density (OD) values. The increased OD value was attenuated by U50,488H(10(-7) mol/l-10(-5) mol/l) in a dose dependent manner. Animals receiving administration of isoprenaline displayed significant fibrosis. The extent of isoprenaline induced left ventricular fibrosis was dramatically reduced in U50,488H treated animals. Increased cardiac fibroblast proliferation and collagen synthesis induced by isoprenaline, as evidenced by increased OD value, (3)H-thymidine, and (3)H-proline incorporation, were significantly reduced in the U50,488H treated group. The specific extracellular matrix proteins, including type I, type III collagen and fibronectin, which increased after administration of isoproterenol, were also attenuated by U50,488H. The abovementioned effects of U50,488H were completely abolished by nor-BNI (nor-binaltorphimine), a selective kappa-opioid receptor antagonist. The enhanced intracellular Ca(2+) transient and L-type Ca(2+) current elicited by isoprenaline in cardiomyocytes were significantly inhibited by U50,488H. This study provides the first morphological evidence of the inhibitory effect of U50,488H on isoprenaline-induced cardiac hypertrophy and fibrosis via kappa-opioid receptor stimulation.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Antihypertensive Agents; Calcium; Calcium Channels, L-Type; Cardiomegaly; Collagen Type I; Collagen Type III; Disease Models, Animal; Dose-Response Relationship, Drug; Fibronectins; Fibrosis; Heart Ventricles; Isoproterenol; Myocytes, Cardiac; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa

cis-4-(Piperazin-1-yl)-5,6,7a,8,9,10,11,11a-octahydrobenzofuro[2,3-h]quinazolin-2-amine, 4 (A-987306) is a new histamine H(4) antagonist. The compound is potent in H(4) receptor binding assays (rat H(4), K(i) = 3.4 nM, human H(4) K(i) = 5.8 nM) and demonstrated potent functional antagonism in vitro at human, rat, and mouse H(4) receptors in cell-based FLIPR assays. Compound 4 also demonstrated H(4) antagonism in vivo in mice, blocking H(4)-agonist induced scratch responses, and showed anti-inflammatory activity in mice in a peritonitis model. Most interesting was the high potency and efficacy of this compound in blocking pain responses, where it showed an ED(50) of 42 mumol/kg (ip) in a rat post-carrageenan thermal hyperalgesia model of inflammatory pain.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Benzofurans; Carrageenan; Disease Models, Animal; Drug Design; Drug Evaluation, Preclinical; Humans; Hyperalgesia; Ligands; Mice; Molecular Structure; Pain; Peritonitis; Quinazolines; Rats; Receptors, G-Protein-Coupled; Receptors, Histamine; Receptors, Histamine H4; Stereoisomerism; Structure-Activity Relationship

Prior activation of the kappa opioid system by repeated stress or agonist administration has been previously shown to potentiate the rewarding properties of subsequently administered cocaine. In the present study, intermittent and uncontrollable footshock, a single session of forced swim, or acute administration of the kappa agonist U50,488 (5 mg/kg) were found to reinstate place preference in mice previously conditioned with cocaine (15 mg/kg) and subsequently extinguished by repeated training sessions without drug.. Stress-induced reinstatement did not occur for mice pretreated with the kappa opioid receptor antagonist norbinaltorphimine (10 mg/kg) and did not occur in mice lacking either kappa opioid receptors (KOR -/-) or prodynorphin (Dyn -/-). In contrast, the initial cocaine conditioning and extinction rates were not significantly affected by disruption of the kappa opioid system. Cocaine-injection also reinstated conditioned place preference in extinguished mice; however, cocaine-primed reinstatement was not blocked by kappa opioid system disruption.. The results suggest that stress-induced drug craving in mice may require activation of the dynorphin/kappa opioid system.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Behavior, Animal; Cocaine-Related Disorders; Conditioning, Operant; Disease Models, Animal; Enkephalins; Extinction, Psychological; Male; Mice; Mice, Inbred C57BL; Mice, Knockout; Protein Precursors; Receptors, Opioid, kappa; Stress, Psychological; Swimming

Periodontal disease is a chronic inflammatory condition of the tooth supporting tissues, the periodontium. Opioids have been shown to account for the relief of various chronic and acute inflammatory conditions. The aim of the present study was to investigate the participation of peripheral opioid receptors in development of periodontal disease.. Morphine and selective agonists and antagonists of opioid receptors were used in an experimental model of ligature-induced periodontal disease in rats. To evaluate the development of disease, the loss of fiber attachment, alveolar bone and number of cells in periodontal tissues were assessed. Measurements of these indicators were obtained by morphometric analysis of histological sections of periodontal-diseased tissues stained with hematoxylin and eosin.. Local administration of either morphine or a selective kappa-opioid agonist for three consecutive days from the onset of periodontal disease reduced the loss of periodontal tissues, without changing the number of leukocytes in inflamed periodontium. Nor-binaltorphimine, a selective kappa-antagonist, reversed the beneficial effects of both morphine and the compound U-50,488 in this model. The use of either an agonist or an antagonist of delta-opioid receptors, however, did not affect disease progression.. Our results showed that the beneficial effect of opioids in periodontal disease depended mainly on the activation of specific kappa-opioid receptors located in the periphery. Activation of such receptors could be considered in the management of periodontal disease, since it would not present the classical central side-effects associated with opioid use.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Opioid; Animals; Chronic Periodontitis; Disease Models, Animal; Male; Morphine; Naltrexone; Narcotic Antagonists; Peripheral Nervous System; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta; Receptors, Opioid, kappa

The depression rate of C fibre-evoked spinal field potentials by spinally applied morphine is increased in two states of spinal hyperexcitation, namely the spinal ligation model (SNL) of neuropathic pain and long-term potentiation (LTP) of C fibre-evoked spinal field potentials. This present work sought to determine opioid receptor subtypes involved in such increase in the SNL model. We recorded spinal field potentials during spinal superfusion with increasing, cumulative concentrations of selective subtype-specific agonists in rats subjected to SNL, as well as in non-ligated animals. The mu opioid receptor (MOR) agonist DAMGO significantly depressed field potentials evoked by C (100 nM) or Adelta fibres (1 microM) both in neuropathic and non-ligated rats, whereas the kappa receptor opioid (KOR) agonist +/-U-50488 was ineffective. The delta opioid receptor (DOR) (D-Ala2)-Deltorphin II was more effective in reducing C fibre-evoked spinal field potentials in rats subjected to SNL (100 nM) than in non-ligated rats (100 microM). Subclinical MOR activation (10 nM DAMGO) produced a leftward shift in (D-Ala2)-Deltorphin II dose-response curve in non-ligated rats (IC50 16.59 +/- 0.99 microM vs 120.3 +/- 1.0 microM in the absence of DAMGO), and isobolar analysis revealed synergistic interaction (interaction index 0.25). MOR blockade (100 microM CTOP) disinhibited C fibre-evoked potentials in neuropathic, but not in basal animals, and partially impeded DOR depression in both groups. DOR blockade (1 mM naltrindole) was ineffective in either group. We show that DOR-mediated depression of spinal responses to peripheral unmyelinated fibre-input is increased in the SNL model, an increase that is contributed to by positive interaction with the spinal MOR.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Behavior, Animal; Disease Models, Animal; Dose-Response Relationship, Drug; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Evoked Potentials; Male; Narcotic Antagonists; Nerve Fibers, Unmyelinated; Neuralgia; Rats; Rats, Sprague-Dawley; Receptors, Opioid, mu; Somatostatin; Spinal Cord

Studies that have evaluated the beneficial effect of pre-ischemic treatment of kappa-opioid receptor agonists have used short-term reperfusion intervals. We examined the long-term impact of the pre-ischemic peripheral injection of U50,488H (trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide), a selective kappa-opioid receptor agonist, on neuronal damage and behavioral deficits following global ischemia in rats. Four groups of ischemic rats were pretreated with various doses of U50,488H (i.p. 0, 5, 15, 30 mg/kg) 15 min prior to vessel occlusion. Two groups of sham-operated animals that received either saline or U50,488H (30 mg/kg) acted as controls. The injection of 30 mg/kg U50,488H led to a 65% increase in CA1 neuron survival 35 days post-ischemia. CA1 neuronal protection translated into significant improvement of ischemia-induced spatial memory deficits assessed in the 8-arm radial maze. However, there was no difference in activity in the open field. We also found that the pre-ischemic intracerebroventricular injection of 5 mug of the delta1-opioid receptor agonist DPDPE ([d-Pen(2,5)]-enkephalin) produced a 59% increase in CA1 neuron survival 7 days post-ischemia. Similar to U50,488H, DPDPE had no significant impact on locomotor activity. These findings support a role for kappa- and delta-opioid receptors in attenuation of ischemia-induced hippocampal damage and cognitive impairments.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Analysis of Variance; Animals; Behavior, Animal; Cell Death; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Administration Routes; Enkephalin, D-Penicillamine (2,5)-; Exploratory Behavior; Hippocampus; Ischemia; Male; Maze Learning; Memory Disorders; Neurons; Rats; Rats, Wistar; Recovery of Function; Time Factors

In order to determine the influence of different opioid receptor subtypes on detrusor overactivity after left middle cerebral artery (MCA) occlusion, cystometric recordings were obtained in conscious rats.. Female Sprague-Dawley rats were used in this study. Control cystometrography was followed by left MCA occlusion. The sham-operated (SO) rats underwent the same procedures except for MCA occlusion. [D-Ala(2), Phe(4), Gly(5)]-enkephalin (DAGO; mu-opioid agonist), [D-Pen(2,5)]-enkephalin (DPDPE; delta1-opioid agonist), deltorpin II (delta2-opioid agonist), and U-50488 (kappa-opioid agonist) were administered intracerebroventricularly at graded doses. The bladder capacity, residual volume, micturition threshold pressure, and bladder contraction pressure were determined. Finally, the volume of the infarction was measured.. The intracerebroventricular administration of DAGO and DPDPE significantly increased the bladder capacity in the cerebrally infarcted (CI) and SO rats, but differences in the changes in bladder capacity between the CI and SO rats were not significant. Deltorpin II did not produce any changes in the bladder capacity in the CI or SO rats at any dose examined. However, the intracerebroventricular administration of U-50488 significantly increased the bladder capacity in the CI rats but not in the SO rats. None of the drugs affected the residual volume, micturition threshold pressure or bladder contraction pressure at any dosage examined. The mean infarcted volumes were not significantly different from those in the vehicle-treated rats.. These results suggest that the opioid receptor subtypes, mu and delta1 in the brain, are related to the micturition reflex. Furthermore, the kappa opioid agonist might be useful for the suppression of detrusor overactivity caused by cerebral infarction.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Cerebral Infarction; Cerebral Ventricles; Disease Models, Animal; Drug Administration Routes; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalin, D-Penicillamine (2,5)-; Female; Oligopeptides; Rats; Rats, Sprague-Dawley; Treatment Outcome; Urinary Bladder, Overactive; Urodynamics

Epilepsy remains a major medical problem of unknown aetiology. Potentially, viruses can be environmental triggers for development of seizures in genetically vulnerable individuals. An estimated half of encephalitis patients experience seizures and approximately 4% develop status epilepticus. Epilepsy vulnerability has been associated with a dynorphin promoter region polymorphism or low dynorphin expression genotype, in man. In animals, the dynorphin system in the hippocampus is known to regulate excitability. The present study was designed to test the hypothesis that reduced dynorphin expression in the dentate gyrus of hippocampus due to periadolescent virus exposure leads to epileptic responses. Encephalitis produced by the neurotropic Borna disease virus in the rat caused epileptic responses and dynorphin to disappear via dentate granule cell loss, failed neurogenesis and poor survival of new neurons. Kappa opioid (dynorphin) agonists prevented the behavioural and electroencephalographic seizures produced by convulsant compounds, and these effects were associated with an absence of dynorphin from the dentate gyrus granule cell layer and upregulation of enkephalin in CA1 interneurons, thus reproducing a neurochemical marker of epilepsy, namely low dynorphin tone. A key role for kappa opioids in anticonvulsant protection provides a framework for exploration of viral and other insults that increase seizure vulnerability and may provide insights into potential interventions for treatment of epilepsy.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Blotting, Northern; Borna Disease; Cell Survival; Disease Models, Animal; Dynorphins; Electroencephalography; Encephalitis, Viral; Enkephalins; Hippocampus; Male; Naloxone; Narcotic Antagonists; Neurons; Rats; Rats, Inbred Lew; Receptors, Opioid, kappa; Seizures

We have previously developed and extensively characterized a convenient and sensitive metric for the quantification of withdrawal responses using Planaria. Planaria are particularly valuable for these studies because of their permeable exteriors and their relevant neurotransmitter systems (e.g., dopaminergic, opioid, and serotonergic). In the present study, we used this metric and mathematically rigorous joint-action analysis to investigate poly-drug withdrawal from fixed-ratio cocaine/kappa-opioid agonist combinations. The D50 (concentration producing half-maximal effect) for cocaine and U-50,488H was 10.3 and 1.02 microg, respectively. The D50 for 19:1 or 1:19 combinations did not differ significantly (p>0.05) from expected additive values (11.6+/-3.0 vs. 9.9+/-1.4 and 1.1+/-0.2 vs. 1.5+/-0.1, respectively), but the 3:1, 1:1, and 1:3 ratios did (34.5+/-6.9 vs. 7.7+/-1.1; 55.1+/-10.0 vs. 5.7+/-0.7; and 40.8+/-8.9 vs. 3.3+/-0.4, respectively), indicating subadditive interaction at these ratios. The finding of subadditivity in this model suggests that abstinence-induced withdrawal from the combination is less intense than that predicted from the individual drug potencies. The concept that certain combinations of drugs leads to attenuated withdrawal might generalize to humans.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Anesthetics, Local; Animals; Behavior, Addictive; Behavior, Animal; Cocaine; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Combinations; Planarians; Receptors, Opioid, kappa; Substance Withdrawal Syndrome

Although the neurochemical mechanisms contributing to alcohol withdrawal seizures are poorly understood, withdrawal seizures probably reflect neuronal hyperexcitability resulting from adaptation to chronic alcohol. Altered kappa-Opioid receptor (KOP-R) signaling has been observed in multiple seizure types; however, a role for this system in ethanol withdrawal seizures has not been systematically characterized. We hypothesized that pharmacological manipulations of the KOP-R would alter withdrawal in mice selectively bred for differences in ethanol withdrawal severity. Withdrawal Seizure-Prone (WSP) and Withdrawal Seizure-Resistant (WSR) mice were made physically dependent using chronic ethanol vapor inhalation, and the effects of the KOP-R antagonist nor-binaltorphimine or agonist U-50,488H on withdrawal severity were examined. Pretreatment with nor-binaltorphimine significantly increased handling-induced convulsion (HIC) severity in withdrawing WSR mice, with no observable effects in withdrawing WSP mice. In contrast, U-50,488H significantly decreased HIC severity in WSP mice, with no effects in WSR mice. During extended withdrawal (i.e. hours 12+), a rebound hyperexcitability was observed in WSP mice given agonist. Thus, administration of a KOP-R antagonist increased withdrawal severity in mice normally resistant to withdrawal seizures, while a KOP-R agonist reduced convulsion severity in animals susceptible to withdrawal seizures. These observations are consistent with differences in the KOP-R system observed in these lines at the molecular level, and suggest the KOP-R system may be a promising therapeutic target for management of ethanol withdrawal seizures. Finally, these findings underscore the importance of determining the potential for rebound increases in withdrawal severity during later withdrawal episodes.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Alcohol-Induced Disorders, Nervous System; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Anticonvulsants; Brain; Central Nervous System Depressants; Disease Models, Animal; Drug Interactions; Drug Synergism; Ethanol; Male; Naltrexone; Receptors, Opioid, kappa; Seizures; Species Specificity; Substance Withdrawal Syndrome; Treatment Outcome

We evaluated the anti-exudative effects (Evan's blue) of mu-, delta- and kappa-opioid receptor agonists in a rat model of carrageenan-induced acute inflammation. The contribution of different components was assessed after the administration of: cyclosporine A, capsaicin, 6-hydroxydopamine, compound 48/80, and specific histamine-receptor antagonists. The results show that the mu-opioid receptor agonists morphine and fentanyl and the delta-opioid receptor agonists DPDPE (enkephalin, [D-Pen(2,5)]) and SNC 80 ((+)-4-[(alpha R)-alpha((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N diethylbenzamide) decrease plasma extravasation in a dose-dependent manner, with a biphasic response. The effects were reversed by specific antagonists, and are predominantly mediated by peripheral opioid receptors. The integrity of sensory and sympathetic fibres is essential for the anti-exudative effects of fentanyl and DPDPE. Histamine and functional histamine H(2) and H(3) receptors are required for morphine and fentanyl (but not DPDPE) inhibition of plasma extravasation, suggesting different mechanism for mu- and delta-opioid receptor agonists. The present findings implicate multiple sites and mechanisms in the anti-exudative effects of exogenous opioids.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; Benzamides; Capsaicin; Carrageenan; Cyclosporine; Disease Models, Animal; Dose-Response Relationship, Drug; Edema; Enkephalin, D-Penicillamine (2,5)-; Extravasation of Diagnostic and Therapeutic Materials; Fentanyl; Hindlimb; Histamine Antagonists; Inflammation; Male; Morphine; Narcotic Antagonists; Oxidopamine; p-Methoxy-N-methylphenethylamine; Piperazines; Rats; Rats, Sprague-Dawley; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu

Although oral administration of L-Dopa remains the best therapy for Parkinson disease, its long-term administration causes the appearance of abnormal involuntary movements such as dyskinesia. Although persistent striatal induction of some genes has already been associated with such pathologic profiles in hemiparkinsonian rats, molecular and cellular mechanisms underlying such long-term adaptations remain to be elucidated. In this study, using a rat model of L-Dopa-induced dyskinesia, we report that activity regulated cytoskeletal (Arc)-associated protein is strongly upregulated in the lesioned striatum and that the extent of its induction further varies according to the occurrence or absence of locomotor sensitization. Moreover, Arc is preferentially induced, along with FosB, nur77, and homer-1a, in striatonigral neurons, which express mRNA encoding the precursor of dynorphin. Given the likely importance of Arc in the regulation of cytoskeleton during synaptic plasticity, its upregulation supports the hypothesis that a relationship exists between cytoskeletal modifications and the longlasting action of chronically administrated L-Dopa.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adrenergic Agents; AIDS-Related Complex; Amphetamine; Analgesics, Non-Narcotic; Animals; Antiparkinson Agents; Behavior, Animal; Carrier Proteins; Central Nervous System Stimulants; Corpus Striatum; Disease Models, Animal; Drug Interactions; Dynorphins; Dyskinesia, Drug-Induced; Functional Laterality; Homer Scaffolding Proteins; Immunohistochemistry; In Situ Hybridization; Levodopa; Male; Motor Activity; Naloxone; Naltrexone; Narcotic Antagonists; Neurons; Oxidopamine; Protein Precursors; Proto-Oncogene Proteins c-fos; Rats; Rats, Wistar; Stereotyped Behavior; Substantia Nigra; Time Factors; Tyrosine 3-Monooxygenase; Up-Regulation

We examined the analgesic and anti-allodynic effects of morphine and U-50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)-benzeneacetamide methanesulfonate salt), a selective kappa-opioid receptor agonist, and the development of tolerance to their effects in neuropathic pain model mice induced by sciatic nerve ligation (SNL). In the tail-pinch method, morphine at 10 mg/kg, s.c. produced a weak analgesic effect in SNL mice; however, U-50,488H at 5 mg/kg, s.c. produced an analgesic effect equipotent to that in normal mice. In contrast, morphine produced an adequate analgesic effect when given either intracerebroventricularly (i.c.v.) or intrathecally (i.t.), but U-50,488H only produced analgesia when given i.t. Repeated administration of morphine (either i.c.v. or i.t.) or U-50,488H (either s.c. or i.t.), did not induce tolerance to the effect. In the static allodynia test with an application of von Frey filaments, both compounds given s.c. suppressed the allodynic effect, but in the dynamic allodynia test involving lightly stroking the plantar surface with a cotton bud, only U-50,488H produced an anti-allodynic effect. Repeated administrations of both compounds did not develop tolerance to these anti-allodynic effects. Thus, U-50,488H was found to be a highly effective at blocking hyperalgesia and allodynia in nerve injury, and these findings suggest that kappa-opioid receptor agonists are attractive pharmacological targets for the control of patients with neuropathic pain.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesia; Animals; Disease Models, Animal; Drug Administration Schedule; Drug Tolerance; Hyperalgesia; Injections, Intraventricular; Injections, Spinal; Injections, Subcutaneous; Male; Mice; Morphine; Pain; Pain Measurement; Physical Stimulation; Receptors, Opioid, kappa; Sciatic Nerve; Sciatic Neuropathy; Species Specificity; Time Factors; Touch

Mice lacking the mu-opioid receptor gene have been used to characterize the role of mu-opioid receptors in nociception and the analgesic actions of opioid agonists. In this study, the authors determined the role of mu-opioid receptors in neuropathic pain behaviors and the effectiveness of mu- and kappa-opioid receptor agonists on this behavior in mice.. The authors studied the behavioral responses of mu-opioid receptor knockout and wild-type mice to thermal and mechanical stimuli before and after neuropathic pain induced by unilateral ligation and section of the L5 spinal nerve. Response to mechanical stimuli was evaluated by determining the frequency of hind paw withdrawal to repetitive stimulation using a series of von Frey monofilaments. Thermal hyperalgesia was assessed by determining the paw withdrawal latencies to radiant heat and frequency of hind paw withdrawal to cooling stimuli. The effects of systemic morphine, the kappa-opioid agonist U50488H, and naloxone on responses to mechanical and thermal stimuli were also studied in spinal nerve-injured mice.. After spinal nerve injury, wild-type mice developed increased responsiveness to mechanical, heat, and cooling stimuli ipsilateral to nerve injury. mu-Opioid receptor knockout mice not only had more prominent mechanical allodynia in the nerve-injured paw, but also expressed contralateral allodynia to mechanical stimuli. Hyperalgesia to thermal stimuli was similar between mu-opioid knockout and wild-type animals. Morphine decreased mechanical allodynia dose dependently (3-30 mg/kg subcutaneous) in wild-type mice--an effect that was attenuated in the heterozygous mice and absent in the homozygous mu-opioid knockout mice. The kappa-opioid agonist U50488H (3-10 mg/kg subcutaneous) attenuated mechanical allodynia in wild-type, heterozygous, and homozygous mu-opioid mice. Naloxone in wild-type mice resulted in enhanced ipsilateral and contralateral allodynia to mechanical stimuli that resembled the pain behavior observed in mu-opioid receptor knockout mice.. The authors' observations indicate that (1) unilateral nerve injury induces a bilateral tonic activation of endogenous mu-opioid receptor-mediated inhibition that attenuates mechanical allodynia but not thermal hyperalgesia, (2) both mu- and kappa-opioid agonists attenuate neuropathic pain in mice, and (3) the antihyperalgesic actions of morphine are mediated primarily via mu-opioid receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Disease Models, Animal; Mice; Morphine; Naloxone; Pain; Reaction Time; Receptors, Opioid, mu; Spinal Nerves

For the first time the involvement of C-Reactive protein (CRP) in early (acute) and delayed ischemic (IPC) and pharmacological (chemical) preconditioning (CPC) in an in vivo model of rat myocardial infarction was presented. Acute IPC was produced by three 5 minute occlusion (ischemia) periods interspersed with 5 minute reperfusion, followed by 30 minute occlusion of the left coronary artery and 2 hour reperfusion injury. Acute CPC was produced by a k-opioid receptor agonist U50488H (5 mg/kg) applied i.v. 15 minutes before 30 minute ischemia/ 2 hour reperfusion. Delayed preconditioning was produced by 30 minute ischemia/ 2 hour reperfusion, induced 24 hour after either ischemic or pharmacological preconditioning. The myocardial ischemia/reperfusion injury was evaluated on the basis of total and cardiac creatine kinase isoenzyme activity, functional recovery of the heart (ECG), infarct size (% IS/RA) and mortality at the end of the experiments. The results obtained showed that: k-opioid receptor agonist U50488H mimics both the acute and delayed IPC in the above experimental protocol; Both acute IPC and most probably CPC act by opening of K(ATP) channels (the effects were blocked by nonspecific ATP-sensitive K channel blocker glybenclamide), and via activation of protein kinase C (a selective protein kinase C inhibitor chelerythrine blocked the efects); C-reactive protein (CRP) was significantly elevated by 54% in non-preconditioned acute ischemia/reperfusion injury. The elevation was more pronounced (82% increase) 24 hour after non-preconditioned ischemia/reperfusion injury. It reflected very well the increase in cardiac isoenzymes, infarct size and mortality of the rats, and can be used as a marker of the severity of myocardial injury in this model; The increase of CRP was prevented by both IPC and CPC in early, and especially in late preconditioning. This confirms the involvement of CRP as a marker in cardiac ischemic/reperfusion injury. It was concluded that in addition to the established involvement of adenosine, bradykinin, opioid and other receptors, a suppression of myocardial CRP/complement production might be involved in the biological mechanism of preconditioning. This could be a promising perspective in clinical interventions against ischemia/reperfusion injuries of the heart.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; C-Reactive Protein; Disease Models, Animal; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Potassium Channels; Rats; Rats, Wistar; Reperfusion Injury

Planarians (Dugesia dorotocephala) that were exposed for 1 h to cocaine (80 microM) or to the kappa-selective opioid receptor agonist U-50,488H (1 microM) displayed an abstinence-induced withdrawal syndrome, indicative of the development of physical dependence, when they were tested in cocaine- (or U-50,488H-) free water, but not when they were tested in cocaine- (or U-50,488H-) containing water. The withdrawal was manifested as a significant (P<0.05) decrease in the rate of planarian spontaneous locomotor activity over a 5-min observation period, using a recently designed metric. Co-exposure of the planarians to D-glucose (1 microM) or to 2-deoxy-D-glucose (2-DG, 1 microM), but not to L-glucose (1 microM), significantly attenuated (P<0.05) the development of physical dependence, shown by an attenuated withdrawal syndrome, from cocaine and U-50,488H. These results suggest that either D-glucose and 2-deoxy-D-glucose compete with a common cocaine and kappa-opioid transport mechanism or that the development of physical dependence (or the inhibition of abstinence-induced withdrawal) in planarians requires energy supplied from glucose metabolism.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adaptation, Physiological; Animals; Behavior, Addictive; Carbohydrate Conformation; Cocaine; Disease Models, Animal; Glucose; Narcotic Antagonists; Opioid-Related Disorders; Planarians; Receptors, Opioid, kappa; Substance Withdrawal Syndrome

Pruritus (itch sensation) is the most common side effect associated with spinal administration of morphine given to humans for analgesia. A variety of agents have been proposed as antipruritics with poorly understood mechanisms and they are effective with variable success. kappa-Opioid agonists possess several actions that are opposite to micro -opioid agonists. We proposed to investigate the role of kappa-opioid receptors (KORs) in morphine-induced scratching and antinociception in monkeys. Scratching responses were counted by observers blinded to treatment. Antinociception was measured by a warm water (50 degrees C) tail-withdrawal assay. Pretreatment with low doses of trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]-cyclohexyl)-benzeneacetamide (U-50488H) (0.032-0.18 mg/kg s.c.), a selective KOR agonist, dose dependently suppressed the s.c. morphine dose-effect curve for scratching and potentiated s.c. morphine-induced antinociception. In addition, s.c. U-50488H attenuated i.t. morphine (10 and 32 micro g)-induced scratching while maintaining or enhancing i.t. morphine-induced antinociception. The combination of s.c. or i.t. morphine with low doses of U-50488H did not cause sedation. More importantly, pretreatment with 3.2 mg/kg nor-binaltorphimine, a selective KOR antagonist, blocked the effects of s.c. U-50488H on both s.c. and i.t. morphine-induced scratching. These results indicate that activation of KOR attenuates morphine-induced scratching without interfering with antinociception in monkeys. This mechanism-based finding provides functional evidence in support of the clinical potential of KOR agonists as antipruritics in the presence of MOR agonist-induced pruritus.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Disease Models, Animal; Drug Interactions; Female; Injections, Spinal; Injections, Subcutaneous; Macaca mulatta; Male; Morphine; Naltrexone; Narcotic Antagonists; Pruritus; Receptors, Opioid, kappa

Antagonistic properties of buprenorphine for epsilon- and micro -opioid receptors were characterized in beta-endorphin- and [d-Ala2,N-Me-Phe4,Gly5-ol]-enkephalin (DAMGO)-induced antinociception, respectively, with the tail-flick test in male ICR mice. epsilon-Opioid receptor agonist beta-endorphin (0.1-1 micro g), micro -opioid receptor agonist DAMGO (0.5-20 ng), or buprenorphine (0.1-20 micro g) administered i.c.v. dose dependently produced antinociception. The antinociception induced by 10 micro g of buprenorphine given i.c.v. was completely blocked by the pretreatment with beta-funaltrexamine (beta-FNA) (0.3 micro g i.c.v.), indicating that the buprenophine-induced antinociception is mediated by the stimulation of the micro -opioid receptor. The antinociceptive effects induced by beta-endorphin (1 micro g i.c.v.) and DAMGO (16 ng i.c.v.) were dose dependently blocked by pretreatment with smaller doses of buprenorphine (0.001-1 micro g i.c.v.), but not by a higher dose of buprenorphine (10 micro g i.c.v.). beta-FNA at a dose (0.3 micro g i.c.v.) that strongly attenuated DAMGO-induced antinociception had no effect on the antinociception produced by beta-endorphin (1 micro g i.c.v.). However, pretreatment with buprenorphine (0.1-10 micro g) in mice pretreated with this same dose of beta-FNA was effective in blocking beta-endorphin-induced antinociception. beta-FNA was 226-fold more effective at antagonizing the antinociception induced by DAMGO (16 ng i.c.v.) than by beta-endorphin (1 micro g i.c.v.). The antinociception induced by delta-opioid receptor agonist [d-Ala2]deltorphin II (10 micro g i.c.v.) or kappa1-opioid receptor agonist trans-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)benzeneacetamine methanesulfonate salt [(-)-U50,488H] (75 micro g i.c.v.) was not affected by pretreatment with buprenorphine (0.1-1.0 micro g i.c.v.). It is concluded that buprenorphine, at small doses, blocks epsilon-opioid receptor-mediated beta-endorphin-induced antinociception and micro -opioid receptor-mediated DAMGO-induced antinociception, and at high doses produces a micro -opioid receptor-mediated antinociception.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Non-Narcotic; Analgesics, Opioid; Animals; beta-Endorphin; Buprenorphine; Disease Models, Animal; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Injections, Intraventricular; Male; Mice; Mice, Inbred ICR; Naltrexone; Narcotic Antagonists; Oligopeptides; Pain; Receptors, Opioid; Receptors, Opioid, delta; Receptors, Opioid, kappa; Receptors, Opioid, mu; Time Factors

Many drug-abusers engage in poly-drug abuse, but there has been relatively little quantification of withdrawal from poly-drug use. Planarians are an advantageous model for these studies due to mammalian-relevant neurotransmitter systems (e.g. dopamine, opioid, and 5-HT). We recently developed a metric that quantified an acute cocaine withdrawal phenomenon in planarians. However, despite much indirect evidence, we lacked direct evidence of a receptor- or carrier-mediated effect. We now report dose-related, naloxone- and nor-binaltorphine-sensitive acute abstinence-induced withdrawal and naloxone-precipitated withdrawal from the kappa-opioid agonist U-50,488H (trans-(+/-)-3,4-dichloro-N-methyl-N-(2-[1-pyrrolidinyl]cyclohexyl)-benzeneacetamide). The less active enantiomer [1R,2R]U-50,488 produced significantly less withdrawal and U-50,488H withdrawal was not due to pH or osmolarity. These data provide pharmacologic evidence of a kappa-opioid receptor-mediated withdrawal phenomenon and neuroadaptation to a pharmacologic stimulus (adaptations in transduction mechanisms) in this model.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Adaptation, Physiological; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Hydrogen-Ion Concentration; Naloxone; Naltrexone; Narcotic Antagonists; Narcotics; Opioid-Related Disorders; Osmolar Concentration; Planarians; Reaction Time; Receptors, Opioid, kappa; Substance Withdrawal Syndrome

To evaluate the possible involvement of kappa opioid receptor-mediated mechanisms in levodopa-induced motor fluctuations, we have investigated the effects of U50,488, a selective kappa opioid agonist, on levodopa-induced motor alterations in rats with unilateral 6-OHDA lesion. Acute and chronic administration of U50,488 has been studied to evaluate the possible reversion or prevention of these levodopa effects. In a first set of experiments, rats were treated with levodopa (25 mg/kg with benserazide, twice daily, ip) for 22 days and, on Day 23 U50,488 (0.5, 1, or 3 mg/kg, i.p.) was administered immediately before levodopa. In a second set of experiments, rats were treated daily for 22 days with levodopa and U50,488 (1 or 3 mg/kg/day, i.p.). The duration of the rotational behavior induced by chronic levodopa decreased after 22 days (P < 0.05). Acute administration of U50,488 on Day 23 reversed this effect when low doses were administered (P < 0.05). Chronic U50,488 administration did not prevent the shortening in response duration induced by levodopa. Our results demonstrate that the kappa opioid receptor agonist U50,488 reverses but does not prevents levodopa-induced motor alterations in parkinsonian rats. These results suggest a role for kappa opioid receptor-mediated mechanisms in the pathophysiology of levodopa-induced motor response complications. These findings suggest that the stimulation of kappa opioid receptors might confer clinical benefit to parkinsonian patients under levodopa therapy suffering from motor complication syndrome.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Antiparkinson Agents; Behavior, Animal; Disease Models, Animal; Drug Administration Schedule; Levodopa; Male; Motor Activity; Oxidopamine; Parkinsonian Disorders; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Time; Treatment Outcome

We investigated the effects of U-50,488H, a kappa-opioid receptor agonist, on the learned helplessness model of depression in mice. Mice pre-exposed to inescapable electric footshock were treated with U-50,488H. Stimulation of the kappa-opioid receptor by U-50,488H (10 mg/kg/day, i.p.) attenuated the escape failure induced by pre-exposure to shock. This attenuation by U-50,488H was blocked by MR2266 (10 mg/kg/day, s.c.), an opioid receptor antagonist. These results suggest that the kappa-opioid system plays an important role in the learned helplessness depression in mice.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Animals; Benzomorphans; Brain; Depression; Depressive Disorder; Disease Models, Animal; Dose-Response Relationship, Drug; Drug Interactions; Helplessness, Learned; Male; Mice; Narcotic Antagonists; Opioid Peptides; Receptors, Opioid, kappa

There is controversy in the literature regarding the involvement of opioid delta (DOP, OP1)- and kappa (KOP,OP2)-receptors in ischemic preconditioning (IPC). Previous studies on this subject in our laboratories and elsewhere have been performed on either isolated heart muscles of experimental animals, or in open-heart surgery rats. To highlight this problem, we introduced an in vivo model of myocardial infarction in rats, which not only allowed electrocardiographic and enzymatic evaluation, but also morphometric assessment of myocardial infarction. In addition to these parameters, a direct receptor ligand study was undertaken, using [3H]-DPDPE, a specific opioid delta-receptor ligand. In our pharmacodynamic studies, we used the selective opioid delta-receptor agonist D-Ala2,D-Leu5 enkephalin (DADLE) and antagonist natrindole. For the evaluation of opioid kappa-receptors, the selective opioid agonist U-50488H and antagonist nor-BNI were employed. Ischemic preconditioning showed the best beneficial effect, compared with pharmacological stimulation of either opioid delta- or kappa-receptors. In normal rat myocytes, two types of opioid delta-receptors exist, namely, low-affinity and high-affinity opioid receptors. In acute myocardial infarction (30-min ischemia), the low-affinity type opioid receptors disappeared, most likely as a result of receptor downregulation due to an excessive release of enkephalins. There was no change in the density of the high-affinity opioid receptor type, but their affinity significantly increased (p < 0.05) by 58%. The radioligand receptor studies showed that opioid delta 1-receptor type was involved not only in triggering, but also in maintaining, the preconditioned state. On the basis of our pharmacodynamic studies, we suggest that both opioid delta 1- and kappa-receptors are involved in the phenomenon of IPC, but with different effects. After 30 min of left coronary artery occlusion, opioid delta-receptor agonist DADLE decreased the infarct size/area at risk from 59.80% in control, untreated, infarcted rats, to 20.40% in treated rats, without a significant effect (p > 0.05) on the occurrence of early cardiac arrhythmias. Opioid kappa-receptor agonist U-50488H produced an opposite effect on the myocardium. It decreased the infarct size/area at risk by 44%, decreased occurrence of early arrhythmias by 77% and also decreased ventricular ectopic beats by 80%. The opioid delta- and kappa-receptor agonists used in this study signifi

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analysis of Variance; Animals; Disease Models, Animal; Hemodynamics; In Vitro Techniques; Ischemic Preconditioning, Myocardial; Male; Myocardial Infarction; Myocardium; Radioligand Assay; Rats; Rats, Wistar; Receptors, Opioid, delta; Receptors, Opioid, kappa

We compared the antinociceptive activity of a kappa-opioid agonist, U-50488H, in streptozotocin-induced diabetic mice with that in non-diabetic mice. Subcutaneously administered U-50488H (3 and 10 mg kg(-1)) showed a more potent antinociceptive effect, as evaluated by the tail-pressure method, in diabetic mice than in non-diabetic mice. Increased antinociceptive activity of U-50488H observed in diabetic mice was also observed in mice given U-50488H intrathecally (3 and 10 microg). However, there were no differences observed between diabetic and non-diabetic mice given U-50488H intracerebroventricularly (3 and 10 microg). Although the antinociceptive effect of U-50488H (3 mg kg(-1), s.c.) in non-diabetic mice was increased by treatment with PD135158 (100 ng, i.c.v.), a cholecystokininB (CCKB) antagonist, the antinociceptive activity of U-50488H which was enhanced in diabetic mice was not influenced by PD135158. Moreover, the increased antinociceptive activity of U-50488H (3 mg kg(-1), s.c.) in diabetic mice diminished when desulfated octapeptide of cholecystokinin (3-100 ng, i.c.v.), a CCKB agonist, was administered. These results suggested that diabetic mice were selectively hyper-responsive to spinal kappa-opioid receptor-mediated antinociception. The function of the analgesia inhibitory system in which cholecystokinin is used as a transmitter might be diminished in diabetic mice.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Analgesics, Non-Narcotic; Animals; Anti-Bacterial Agents; Cholecystokinin; Diabetes Mellitus; Disease Models, Animal; Dose-Response Relationship, Drug; Male; Mice; Pain; Streptozocin

By acting on peripheral opioid receptors, opioid agonists can attenuate nociceptive responses induced by a variety of agents.. This study was conducted to characterize capsaicin-induced thermal hyperalgesia in rats and to evaluate the hypothesis that local administration of either mu or kappa opioid agonists (fentanyl and U50,488, respectively) can attenuate capsaicin-induced nociception.. Capsaicin was administered s. c. in the tail of rats to evoke a nociceptive response, which was measured by the warm-water tail-withdrawal procedure. Either fentanyl or U50,488 was co-administered with capsaicin in the tail to evaluate local antinociceptive effects. In addition, the local antagonism study was performed to confirm the site of action of both opioid agonists.. Capsaicin (0.3-10 microg) dose dependently produced thermal hyperalgesia manifested as reduced tail-withdrawal latencies in 45 degrees C water. Co-administration of either fentanyl (0.32-3.2 microg) or U50,488 (10-100 microg) with capsaicin (3 microg) attenuated capsaicin-induced hyperalgesia in a dose-dependent manner. Furthermore, this local antinociception was antagonized by small doses (10-100 microg) of an opioid antagonist, quadazocine, applied s.c. in the tail. However, the locally effective doses of quadazocine, when applied s.c. in the back (i.e., around the scapular region), did not antagonize either fentanyl or U50,488.. In this experimental pain model, activation of peripheral mu or kappa opioid receptors can attenuate capsaicin-induced thermal hyperalgesia in rats. It supports the notion that peripheral antinociception can be achieved by local administration of analgesics into the injured tissue without producing central side effects.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics, Non-Narcotic; Analgesics, Opioid; Anesthesia, Local; Animals; Azocines; Capsaicin; Disease Models, Animal; Dose-Response Relationship, Drug; Fentanyl; Hot Temperature; Hyperalgesia; Injections, Subcutaneous; Male; Narcotic Antagonists; Pain; Pain Measurement; Rats; Rats, Wistar; Receptors, Opioid, kappa; Receptors, Opioid, mu

The role of the mu-opioid receptor in immune function was investigated using mu-opioid receptor knockout mice (MOR-KO). Morphine modulation of several immune functions, including macrophage phagocytosis and macrophage secretion of TNF-alpha, was not observed in the MOR-KO animals, suggesting that these functions are mediated by the classical mu-opioid receptor. In contrast, morphine reduction of splenic and thymic cell number and mitogen-induced proliferation were unaffected in MOR-KO mice, as was morphine inhibition of IL-1 and IL-6 secretion by macrophages. These latter results are consistent with morphine action on a naloxone insensitive morphine receptor, a conclusion supported by previous studies characterizing a nonopioid morphine binding site on immune cells. Alternatively, morphine may act either directly or indirectly on these cells, by a mechanism mediated by either delta or kappa opioid receptors.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Binding, Competitive; Disease Models, Animal; Drug Implants; Exons; Gene Targeting; Immune System; Immunosuppression Therapy; Interleukin-2; Ligands; Macrophage Activation; Macrophages, Peritoneal; Mice; Mice, Knockout; Mitogens; Morphine; Naltrexone; Organ Size; Phagocytosis; Receptors, Opioid, mu; Spleen; Substance-Related Disorders; Thymidine; Thymus Gland; Tumor Necrosis Factor-alpha

The blockade of veratrine-stimulated phosphoinositide breakdown in rat cerebral cortical miniprisms has been used as a model of drug action on voltage-dependent sodium channels. The kappa-opioid agonists bremazocine, (+/-)- and (+)-trans-U-50488, U-62066 (spiradoline) and U-69593 inhibited the response to veratrine with IC50 values of 35, 13, 15, 9, and > 100 microM, respectively. Bremazocine, at concentrations inhibiting the response to veratrine, did not inhibit the phosphoinositide breakdown response to the sodium ionophore monensin, indicating the specificity of the assay for sodium channels. The inhibitory actions of bremazocine upon veratrine-stimulated phosphoinositide breakdown were not antagonised by naloxone. This study thus confirms previous data suggesting that the kappa-opioid receptor agonists can affect Na(+)-channel function in a manner unrelated to their actions at kappa-opioid receptors. However, for the compounds tested, such effects are only found at rather high concentrations of the compounds.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Benzeneacetamides; Benzomorphans; Brain; Disease Models, Animal; Inositol Phosphates; Naloxone; Pyrrolidines; Rats; Receptors, Opioid, kappa; Sodium Channels

U-50488H, a selective opioid kappa receptor agonist has been shown to be a neuroprotective agent in animal models of spinal cord injury. The mechanism of action of U-50488H is not known. Methylprednisolone, the only neuroprotective drug proven in patients with acute spinal cord injury may prevent the secondary injury after an initial trauma. Secondary vascular injury develops after experimental spinal cord trauma. In this study we examined the effects of U-50488H on post-traumatic vascular injury based on the measurement of vascular permeability, edema and neutrophil infiltration in a rat spinal cord injury model. Vascular permeability was assessed by vascular extravasation of fluorescein isothiocyanate conjugated dextran (FITC-D), a macromolecular tracer. Tissue edema was determined by percentage water content and neutrophil infiltration by myeloperoxidase (MPO) activity, a marker enzyme for neutrophils. U-50488H at doses of 5, 10, 20 and 40 mg/kg i.p. administered twice (0.5 h before and 0.5 h after trauma) reduced vascular permeability in a dose-dependent manner. More frequent dosing (10 mg/kg, 0.5 h before and 0.5, 2, 8 and 22 h after injury) reduced vascular permeability 24 h after injury. U-50488H also reduced edema formation but did not affect neutrophil infiltration. Results from this study raise the possibility that the neuroprotective effect of U-50488H involves a secondary vascular event.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Blood Vessels; Capillary Permeability; Disease Models, Animal; Edema; Female; Neutrophils; Pyrrolidines; Rats; Rats, Sprague-Dawley; Receptors, Opioid, kappa; Spinal Cord Injuries

The aim was to evaluate the effects of an opiate agonist (U50,488H) and an opiate antagonist (naloxone) in myocardial ischaemia.. A left thoracotomy was performed and the left coronary artery was ligated in adult Sprague-Dawley rats of either sex (350-400 g). Blood pressure, heart rate and electrocardiogram were measured before and after injections of U50,488H or naloxone and throughout the 30 min postligation period.. Following coronary artery occlusion, all rats in the control group developed arrhythmias, bradycardia, and hypotension. U50,488H potentiated and naloxone attenuated the ischaemia induced arrhythmias, bradycardia, and hypotension.. The potentiating and blocking effects of U50,488H and naloxone, respectively, suggest that endogenous opioid peptides are involved in the pathophysiology of myocardial ischaemia and play an important role in ischaemic heart disease.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Analgesics; Animals; Arrhythmias, Cardiac; Blood Pressure; Coronary Disease; Disease Models, Animal; Female; Heart Rate; Male; Naloxone; Pyrrolidines; Rats; Rats, Inbred Strains

Subcutaneous or i.c.v. administration of U50,488, a highly selective kappa opioid agonist, resulted in a dose-and time-dependent anticonvulsant action in rats. The anticonvulsant effect was seizure-specific; thus, U50,488 protected against supramaximal electroshock seizures but failed to raise the threshold of flurothyl-induced convulsions. The ED50 for s.c. U50,488 was 8.6 mg/kg, with a duration of action longer than 8 hr. In contrast, the ED50 for i.c.v. U50,488 was 103.8 micrograms, lasting approximately 1 hr. The anticonvulsant effect of U50,488 was partially antagonized by high (10.0 mg/kg), but not low (1.0 mg/kg), doses of s.c. administered naloxone. Results indicate that U50,488 is an efficacious, long-acting anticonvulsant against supramaximal, but not chemical threshold, seizures in rats. Furthermore, the results with naloxone suggest that this effect of U50,488 is mediated by non-mu (probably kappa) binding sites. This structurally novel nonpeptide opioid may offer new insights into the development of therapeutically effective agents in the treatment of grand mal or partial epilepsies.

Topics: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer; Animals; Anticonvulsants; Behavior, Animal; Disease Models, Animal; Dose-Response Relationship, Drug; Electroshock; Flurothyl; Male; Phenytoin; Pyrrolidines; Rats; Receptors, Opioid; Receptors, Opioid, kappa; Seizures