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Acetaminophen Relieves Inflammatory Pain through CB 1 Cannabinoid Receptors in the Rostral Ventromedial Medulla. J Neurosci 2017; 38:322-334. [PMID: 29167401 DOI: 10.1523/jneurosci.1945-17.2017] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 10/27/2017] [Accepted: 11/14/2017] [Indexed: 12/30/2022] Open
Abstract
Acetaminophen (paracetamol) is a widely used analgesic and antipyretic drug with only incompletely understood mechanisms of action. Previous work, using models of acute nociceptive pain, indicated that analgesia by acetaminophen involves an indirect activation of CB1 receptors by the acetaminophen metabolite and endocannabinoid reuptake inhibitor AM 404. However, the contribution of the cannabinoid system to antihyperalgesia against inflammatory pain, the main indication of acetaminophen, and the precise site of the relevant CB1 receptors have remained elusive. Here, we analyzed acetaminophen analgesia in mice of either sex with inflammatory pain and found that acetaminophen exerted a dose-dependent antihyperalgesic action, which was mimicked by intrathecally injected AM 404. Both compounds lost their antihyperalgesic activity in CB1-/- mice, confirming the involvement of the cannabinoid system. Consistent with a mechanism downstream of proinflammatory prostaglandin formation, acetaminophen also reversed hyperalgesia induced by intrathecal prostaglandin E2 To distinguish between a peripheral/spinal and a supraspinal action, we administered acetaminophen and AM 404 to hoxB8-CB1-/- mice, which lack CB1 receptors from the peripheral nervous system and the spinal cord. These mice exhibited unchanged antihyperalgesia indicating a supraspinal site of action. Accordingly, local injection of the CB1 receptor antagonist rimonabant into the rostral ventromedial medulla blocked acetaminophen-induced antihyperalgesia, while local rostral ventromedial medulla injection of AM 404 reduced hyperalgesia in wild-type mice but not in CB1-/- mice. Our results indicate that the cannabinoid system contributes not only to acetaminophen analgesia against acute pain but also against inflammatory pain, and suggest that the relevant CB1 receptors reside in the rostral ventromedial medulla.SIGNIFICANCE STATEMENT Acetaminophen is a widely used analgesic drug with multiple but only incompletely understood mechanisms of action, including a facilitation of endogenous cannabinoid signaling via one of its metabolites. Our present data indicate that enhanced cannabinoid signaling is also responsible for the analgesic effects of acetaminophen against inflammatory pain. Local injections of the acetaminophen metabolite AM 404 and of cannabinoid receptor antagonists as well as data from tissue-specific CB1 receptor-deficient mice suggest the rostral ventromedial medulla as an important site of the cannabinoid-mediated analgesia by acetaminophen.
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Schröder W, Alique M, Herrero J. Effects of the mas-related gene (Mrg) C receptor agonist BAM6-22 on nociceptive reflex activity in naive, monoarthritic and mononeuropathic rats after intraplantar and intrathecal administration. Eur J Pharmacol 2016; 770:147-53. [DOI: 10.1016/j.ejphar.2015.11.042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 11/19/2015] [Accepted: 11/20/2015] [Indexed: 11/25/2022]
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Interaction of the adenosine A1 receptor agonist N6-cyclopentyladenosine and κ-opioid receptors in rat spinal cord nociceptive reflexes. Behav Pharmacol 2014; 25:741-9. [DOI: 10.1097/fbp.0000000000000091] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Sukhtankar DD, Lee H, Rice KC, Ko MC. Differential effects of opioid-related ligands and NSAIDs in nonhuman primate models of acute and inflammatory pain. Psychopharmacology (Berl) 2014; 231:1377-87. [PMID: 24217900 PMCID: PMC3954905 DOI: 10.1007/s00213-013-3341-0] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2013] [Accepted: 10/09/2013] [Indexed: 11/30/2022]
Abstract
RATIONALE 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. OBJECTIVE 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). RESULTS 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. CONCLUSION 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.
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Affiliation(s)
- Devki D. Sukhtankar
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA,Corresponding authors: Dr. D. Sukhtankar () and Dr. H. Lee ()
| | - Heeseung Lee
- Department of Anesthesiology and Pain Medicine, School of Medicine, Ewha Womans University, Seoul 158-710, S. Korea,Corresponding authors: Dr. D. Sukhtankar () and Dr. H. Lee ()
| | - Kenner C. Rice
- Chemical Biology Research Branch, National Institute on Drug Abuse, Bethesda, MD 20892, USA
| | - Mei-Chuan Ko
- Department of Physiology and Pharmacology, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA,Center for Comparative Medicine Research, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA
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Queiroz-Neto A, Zamur G, Mataqueiro MI, D'Angelis FH, Araújo RA, Silva MH, Basile RC, Ferraz GC. Behavioral and Antinociceptive Effects of Alfentanil, Butorphanol, and Flunixin in Horses. J Equine Vet Sci 2013. [DOI: 10.1016/j.jevs.2013.04.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Ramos-Zepeda G, Herrero JF. Interaction of the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) and opioid receptors in spinal cord nociceptive reflexes. Life Sci 2013; 93:233-9. [PMID: 23810661 DOI: 10.1016/j.lfs.2013.06.017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2013] [Revised: 05/13/2013] [Accepted: 06/11/2013] [Indexed: 11/29/2022]
Abstract
AIMS We previously observed that the adenosine A1 receptor agonist N6-cyclopentyladenosine (CPA) is a very effective antinociceptive agent on intact but not on spinalized adult rats with inflammation. Since a close connection between opioid and adenosine A1 receptors has been described, we studied a possible relationship between these systems in the spinal cord. MAIN METHODS CPA-mediated antinociception was challenged by the selective adenosine A1 receptor antagonist 8-cyclopentyl-1, 3-dimethylxanthine (CPT) and by the opioid receptor antagonist naloxone on male adult Wistar rats with carrageenan-induced inflammation. Withdrawal reflexes activated by noxious mechanical and electrical stimulation were recorded using the single motor technique in intact and sham-spinalized animals. KEY FINDINGS CPA was very effective in intact and sham spinalized rats but not in spinalized animals. Full reversal of CPA antinociception was observed with i.v. 1mg/kg of naloxone but not with 20mg/kg of CPT i.v. in responses to noxious mechanical and electrical stimulation. CPT fully prevented CPA from any antinociceptive action whereas naloxone did not modify CPA activity. These results suggest a centrally-mediated action, since CPA depressed the wind-up phenomenon which is derived of the activity of spinal cord neurons. SIGNIFICANCE The present study provides strong in vivo evidence of an antinociceptive activity mediated by the adenosine A1 receptor system in the spinal cord, linked to an activation of opioid receptors in adult animals with inflammation.
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Previous administration of naltrexone did not change synergism between paracetamol and tramadol in mice. Pharmacol Biochem Behav 2012; 102:72-6. [DOI: 10.1016/j.pbb.2012.03.008] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2011] [Revised: 02/19/2012] [Accepted: 03/10/2012] [Indexed: 11/22/2022]
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Pickering G, Moustafa F, Desbrandes S, Cardot JM, Roux D, Dubray C. Paracetamol and opioid pathways: a pilot randomized clinical trial. Fundam Clin Pharmacol 2011; 27:339-45. [PMID: 22092536 DOI: 10.1111/j.1472-8206.2011.01010.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Previous studies suggest that the antinociceptive action of paracetamol (acetaminophen, APAP) might involve descending inhibitory pain pathways and the opioidergic system: this study explores this issue in humans with naloxone, the opioid antagonist. After ethical approval, 12 healthy male volunteers were included in this randomized, controlled, double-blind, crossover, four-arm study. They were administered intravenous paracetamol (APAP 1 g) or saline (placebo, pl) followed at 100 min with IV naloxone (Nal 8 mg) or saline, every week for 4 weeks. The amplitude of cerebral potentials evoked by thermal/painful stimuli applied on the arm was recorded nine times over 150 min, witnessing of pain integration at central level. Amplitude changes as well as areas under the curve (AUCs) over 150 min were compared for the four treatments by repeated measures ANOVA (significance 0.05). Amplitude changes were significant for APAP/pl vs. pl/pl at t150: -44% (95%CI -58 to -30) vs. -27% (95%CI -37 to -17; P < 0.05) but not vs. APAP/Nal. AUC (0-150) of APAP/pl is significantly different from pl/pl (-3452%.min (95%CI -4705 to -2199) vs. -933% min (95%CI -2273 to 407; P = 0.015) but not from APAP/Nal (-1731% min (95%CI -3676 to 214; P = 0.08) and other treatments. AUC (90-150) is not significantly different. This pilot study shows for the first time in human volunteers that naloxone does not inhibit paracetamol antinociception, suggesting no significant implication of the opioid system in paracetamol mechanism of action: this needs be confirmed on a larger number of subjects.
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Affiliation(s)
- Gisèle Pickering
- CHU Clermont-Ferrand, Centre de Pharmacologie Clinique, F-63003 Clermont-Ferrand, France.
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Subeffective doses of nitroparacetamol (NCX-701) enhance the antinociceptive activity of the α2-adrenoceptor agonist medetomidine. Pharmacol Biochem Behav 2011; 99:385-90. [DOI: 10.1016/j.pbb.2011.05.022] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Revised: 05/13/2011] [Accepted: 05/19/2011] [Indexed: 11/20/2022]
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Abstract
There is a legal requirement to provide analgesia for velvet antler removal in New Zealand. Currently, this is achieved using local anaesthetic blockade, with or without systemically administered sedative/analgesic agents, or by compression in 1-year-old stags. Lignocaine hydrochloride 2% is most commonly used and is most effective when administered as a high-dose ring block. Combinations of various amino-amide local anaesthetic agents can achieve rapid onset and prolonged duration of analgesia, though concerns about drug residues and carcinogenic potential of a lignocaine metabolite have led to consideration of the amino-ester family of local anaesthetics as alternatives. Systemically administered analgesics, including opioids, alpha-2-adrenergic agents and ketamine provide dose-dependent sedation and analgesia. However, none are sufficient, alone or in combination, to produce surgical analgesia at currently recommended dose rates and when reversal agents are given, analgesic effects are usually reversed as well as sedation. Thus, local anaesthetic blockade is still indicated, though the potential for drug or drug-metabolite residues in velvet antler remains a concern. The need for and effectiveness of non-steroidal anti-inflammatory drugs (NSAIDs) for post-operative analgesia requires investigation. Amitriptyline, locally administered opioid agonists, tramadol and other systemically administered agents may warrant future investigation for surgical and post-operative analgesia for velvet antler removal.
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Affiliation(s)
- V P Walsh
- Institute of Veterinary Animal and Biomedical Sciences, Massey University, Private Bag 11222, Palmerston North, New Zealand.
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Choi CH, Kim WM, Lee HG, Jeong CW, Kim CM, Lee SH, Yoon MH. Roles of opioid receptor subtype in the spinal antinociception of selective cyclooxygenase 2 inhibitor. Korean J Pain 2010; 23:236-41. [PMID: 21217886 PMCID: PMC3000619 DOI: 10.3344/kjp.2010.23.4.236] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 10/01/2010] [Accepted: 10/05/2010] [Indexed: 11/05/2022] Open
Abstract
BACKGROUND Selective inhibitors of cyclooxygenase (COX)-2 are commonly used analgesics in various pain conditions. Although their actions are largely thought to be mediated by the blockade of prostaglandin (PG) biosynthesis, evidences suggesting endogenous opioid peptide link in spinal antinociception of COX inhibitor have been reported. We investigated the roles of opioid receptor subtypes in the spinal antinociception of selective COX-2 inhibitor. METHODS To examine the antinociception of a selective COX-2 inhibitor, DUP-697 was delivered through an intrathecal catheter, 10 minutes before the formalin test in male Sprague-Dawley rats. Then, the effect of intrathecal pretreatment with CTOP, naltrindole and GNTI, which are µ, δ and κ opioid receptor antagonist, respectively, on the analgesia induced by DUP-697 was assessed. RESULTS Intrathecal DUP-697 reduced the flinching response evoked by formalin injection during phase 1 and 2. Naltrindole and GNTI attenuated the antinociceptive effect of intrathecal DUP-697 during both phases of the formalin test. CTOP reversed the antinociception of DUP-697 during phase 2, but not during phase 1. CONCLUSIONS Intrathecal DUP-697, a selective COX-2 inhibitor, effectively relieved inflammatory pain in rats. The δ and κ opioid receptors are involved in the activity of COX-2 inhibitor on the facilitated state as well as acute pain at the spinal level, whereas the µ opioid receptor is related only to facilitated pain.
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Affiliation(s)
- Cheol Hun Choi
- Department of Anesthesiology and Pain Medicine, Chonnam National University Hospital, Gwangju, Korea
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Rezende RM, Paiva-Lima P, Dos Reis WGP, Camêlo VM, Bakhle YS, de Francischi JN. Celecoxib induces tolerance in a model of peripheral inflammatory pain in rats. Neuropharmacology 2010; 59:551-7. [PMID: 20691196 DOI: 10.1016/j.neuropharm.2010.07.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2010] [Revised: 06/29/2010] [Accepted: 07/26/2010] [Indexed: 02/02/2023]
Abstract
Celecoxib is a non-steroidal anti-inflammatory drug (NSAID) that selectively inhibits cyclooxygenase-2 (COX-2). Like most NSAIDs, celecoxib exhibits analgesic effects in models of inflammatory pain but these appear to be dependent on endogenous opioid release. Therefore, this study has assessed the ability of celecoxib to induce tolerance in rats, comparable to that induced by morphine. Rats were injected subcutaneously (s.c.) twice daily with divided doses of celecoxib, morphine or indomethacin. Inflammation was induced in one hind paw of rats by injecting prostaglandin E(2) (PGE(2); 200 ng) 30 min after drug administration, on days 1, 3, 5 and 6 or 7. Nociceptive thresholds to mechanical stimulation were measured 3 h after PGE(2) injection, on the same days. On days 6 or 7, analgesic effects of the full doses of test drugs were assessed. Celecoxib-induced tolerance, as did morphine, an effect not shown by another NSAID, indomethacin. Cross-tolerance between celecoxib and morphine was observed as they did not induce analgesia when animals were chronically treated with morphine or celecoxib, respectively. In addition, tolerance to celecoxib's analgesic effects persisted for at least two days after the end of the chronic treatment with celecoxib. Naltrexone prevented induction of tolerance to morphine or celecoxib. The present results strengthen the possibility that celecoxib has also mechanisms of analgesia unrelated to COX inhibition but dependent on endogenous opioid release. Our results also imply the existence of a new class of analgesics without the deleterious effects of COX inhibitors.
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Affiliation(s)
- Rafael Machado Rezende
- Federal University of Minas Gerais, Institute of Biological Sciences, Department of Pharmacology, Laboratory of Inflammation and Pain, Av. Antonio Carlos 6627, Pampulha, Belo Horizonte, Brazil
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Acute Pressure Block of the Sciatic Nerve Relieves Clinical Pain But Not Cold Pressor Pain. Clin J Pain 2010; 26:332-8. [PMID: 20393269 DOI: 10.1097/ajp.0b013e3181c8fc68] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Woode E, Danquah C, Boakye-Gya E, Ansah C, Ainooson G. Antinociceptive Effects of an Ethanolic Extract of Capparis erythrocarpos Isert Roots in the Mice Formalin Test. INT J PHARMACOL 2009. [DOI: 10.3923/ijp.2009.354.361] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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15
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The analgesic actions of centrally administered celecoxib are mediated by endogenous opioids. Pain 2009; 142:94-100. [DOI: 10.1016/j.pain.2008.12.005] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2008] [Revised: 10/22/2008] [Accepted: 12/02/2008] [Indexed: 02/02/2023]
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16
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Ruggieri V, Vitale G, Pini LA, Sandrini M. Differential involvement of opioidergic and serotonergic systems in the antinociceptive activity of N-arachidonoyl-phenolamine (AM404) in the rat: comparison with paracetamol. Naunyn Schmiedebergs Arch Pharmacol 2008; 377:219-29. [PMID: 18404260 DOI: 10.1007/s00210-008-0284-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2008] [Accepted: 03/06/2008] [Indexed: 10/22/2022]
Abstract
It is recognized that paracetamol undergoes a metabolic transformation to N-arachydonylphenolamine (AM404), a CB(1) receptor ligand and anandamide uptake inhibitor. Using hot-plate and paw pressure tests, we decided to establish whether AM404 may act through opioidergic and serotonergic mechanisms. Thus, we pretreated rats with opioid mu(1) (naloxonazine) and kappa (MR2266) or 5-HT(1A) (NAN-190), 5-HT(2) (ketanserin), and 5-HT(3) (ondansetron) receptor antagonists. We investigated the possible changes in 5-hydroxyindoleacetic acid/serotonin ratio in the frontal cortex and pons. The antinociceptive effect of AM404 (10 mg/kg, intraperitoneally) or paracetamol (400 mg/kg, intraperitoneally) in either test was abolished by naloxonazine or MR2266. Ondansetron prevented AM404 activity; NAN-190 and ketanserin were ineffective. Ketanserin antagonized paracetamol activity; NAN-190 and ondansetron were inactive. AM404 did not change serotonergic activity, while paracetamol decreased serotonin turnover. The diverse antinociceptive potency of the compounds might be explained by the different influence on the serotonergic system, despite a similar involvement of opioidergic one.
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MESH Headings
- Acetaminophen/pharmacology
- Analgesics, Non-Narcotic/pharmacology
- Animals
- Arachidonic Acids/pharmacology
- Frontal Lobe/drug effects
- Frontal Lobe/metabolism
- Hydroxyindoleacetic Acid/metabolism
- Male
- Pain/drug therapy
- Pain Measurement
- Pons/drug effects
- Pons/metabolism
- Rats
- Rats, Wistar
- Receptor, Serotonin, 5-HT1A/drug effects
- Receptor, Serotonin, 5-HT1A/metabolism
- Receptors, Opioid, kappa/drug effects
- Receptors, Opioid, kappa/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Receptors, Serotonin, 5-HT2/drug effects
- Receptors, Serotonin, 5-HT2/metabolism
- Receptors, Serotonin, 5-HT3/drug effects
- Receptors, Serotonin, 5-HT3/metabolism
- Serotonin/metabolism
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Affiliation(s)
- Valentina Ruggieri
- Sect. of Pharmacology, Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via G.Campi 287, 41100 Modena, Italy
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Bertolini A, Ferrari A, Ottani A, Guerzoni S, Tacchi R, Leone S. Paracetamol: new vistas of an old drug. CNS DRUG REVIEWS 2007; 12:250-75. [PMID: 17227290 PMCID: PMC6506194 DOI: 10.1111/j.1527-3458.2006.00250.x] [Citation(s) in RCA: 348] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Paracetamol (acetaminophen) is one of the most popular and widely used drugs for the treatment of pain and fever. It occupies a unique position among analgesic drugs. Unlike NSAIDs it is almost unanimously considered to have no antiinflammatory activity and does not produce gastrointestinal damage or untoward cardiorenal effects. Unlike opiates it is almost ineffective in intense pain and has no depressant effect on respiration. Although paracetamol has been used clinically for more than a century, its mode of action has been a mystery until about one year ago, when two independent groups (Zygmunt and colleagues and Bertolini and colleagues) produced experimental data unequivocally demonstrating that the analgesic effect of paracetamol is due to the indirect activation of cannabinoid CB(1) receptors. In brain and spinal cord, paracetamol, following deacetylation to its primary amine (p-aminophenol), is conjugated with arachidonic acid to form N-arachidonoylphenolamine, a compound already known (AM404) as an endogenous cannabinoid. The involved enzyme is fatty acid amide hydrolase. N-arachidonoylphenolamine is an agonist at TRPV1 receptors and an inhibitor of cellular anandamide uptake, which leads to increased levels of endogenous cannabinoids; moreover, it inhibits cyclooxygenases in the brain, albeit at concentrations that are probably not attainable with analgesic doses of paracetamol. CB(1) receptor antagonist, at a dose level that completely prevents the analgesic activity of a selective CB(1) receptor agonist, completely prevents the analgesic activity of paracetamol. Thus, paracetamol acts as a pro-drug, the active one being a cannabinoid. These findings finally explain the mechanism of action of paracetamol and the peculiarity of its effects, including the behavioral ones. Curiously, just when the first CB(1) agonists are being introduced for pain treatment, it comes out that an indirect cannabino-mimetic had been extensively used (and sometimes overused) for more than a century.
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Affiliation(s)
- Alfio Bertolini
- Division of Toxicology and Clinical Pharmacology, University of Modena and Reggio Emilia, Modena, Italy.
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Romero-Sandoval EA, Molina C, Alique M, Moreno-Manzano V, Lucio FJ, Herrero JF. Vitamin A active metabolite, all-trans retinoic acid, induces spinal cord sensitization. I. Effects after oral administration. Br J Pharmacol 2006; 149:56-64. [PMID: 16847436 PMCID: PMC1629405 DOI: 10.1038/sj.bjp.0706829] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
BACKGROUND AND PURPOSE Retinoic acid is an active metabolite of vitamin A involved in the modulation of the inflammatory and nociceptive responses. The aim of the present study was to analyze the properties of spinal cord neuronal responses of male Wistar rats treated with all-trans retinoic acid (ATRA) p.o. in the normal situation and under carrageenan-induced inflammation. We also studied the expression and distribution of cyclooxygenases (COX) in the spinal cord. EXPERIMENTAL APPROACH Properties of spinal cord neurons were studied by means of the single motor unit technique. The expression of COX enzymes in the spinal cord was assessed by Western blot analysis and immunohistochemistry. KEY RESULTS Intensity thresholds for mechanical and electrical stimulation (C-fibers) were significantly lower in animals treated with ATRA than vehicle, either in normal rats or in rats with inflammation. The size of cutaneous receptive fields was also larger in animals treated with ATRA in the normal and inflammatory conditions. The expression of COX-2 enzyme, but not COX-1, was significantly higher in animals treated with ATRA. COX-2 labeling was observed in dorsal horn cells and in ventral horn motoneurons. CONCLUSIONS AND IMPLICATIONS In conclusion, the oral treatment with ATRA in rats induces a sensitization-like effect on spinal cord neuronal responses similar to that observed in animals with inflammation and might explain the enhancement of allodynia and hyperalgesia observed in previously published behavioral experiments. The mechanism of action involves an over-expression of COX-2, but not COX-1, in dorsal and ventral horn areas of the lumbar spinal cord.
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Affiliation(s)
- E A Romero-Sandoval
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - C Molina
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - M Alique
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - V Moreno-Manzano
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - F J Lucio
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - J F Herrero
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
- Author for correspondence:
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França DS, Ferreira-Alves DL, Duarte IDG, Ribeiro MC, Rezende RM, Bakhle YS, Francischi JN. Endogenous opioids mediate the hypoalgesia induced by selective inhibitors of cyclo-oxygenase 2 in rat paws treated with carrageenan. Neuropharmacology 2006; 51:37-43. [PMID: 16620880 DOI: 10.1016/j.neuropharm.2006.02.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2005] [Revised: 02/17/2006] [Accepted: 02/21/2006] [Indexed: 02/02/2023]
Abstract
Mechanical hyperalgesia induced in rat paws by carrageenan (250microg) was modified by pre-treatment with three selective inhibitors of cyclo-oxygenase-2 (COX-2); celecoxib, rofecoxib and SC236. These inhibitors raised the nociceptive threshold above the normal, non-inflamed, level, inducing a state of hypoalgesia. Such hypoalgesia was observed in different strains of rat (Holtzman, Wistar and Sprague-Dawley) and after different modes of administration of the COX-2 inhibitor (locally, in the paw, or systemically). A selective inhibitor of COX-1 (SC 560; 1-10mg kg(-1)) decreased hyperalgesia but did not induce hypoalgesia. Pre-treatment with naltrexone (3mg kg(-1)), an opioid receptor antagonist, did not affect carrageenan-induced hyperalgesia but abolished the hypoalgesic effects of COX-2 inhibitors, without diminishing the anti-hyperalgesic effect of indomethacin. In rats made tolerant to the anti-nociceptive effects of morphine, all anti-nociceptive effects of SC236 were abolished but the anti-hyperalgesic effects of indomethacin or SC 560 were unaffected. We conclude that, in our model of inflammatory hyperalgesia, the anti-nociceptive effect of selective COX-2 inhibitors involved the participation of endogenous opioids.
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Affiliation(s)
- Dorothéa S França
- Departamento de Farmacologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Av. Antônio Carlos 6627, Campus da Pampulha, 31270901 Belo Horizonte, Minas Gerais, Brazil
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20
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Molina C, Herrero JF. The influence of the time course of inflammation and spinalization on the antinociceptive activity of the α2-adrenoceptor agonist medetomidine. Eur J Pharmacol 2006; 532:50-60. [PMID: 16473347 DOI: 10.1016/j.ejphar.2005.12.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2005] [Revised: 12/14/2005] [Accepted: 12/15/2005] [Indexed: 11/27/2022]
Abstract
The purpose of the present study was to investigate the influence of the time course of inflammation and the implication of spinal and supraspinal sites on the antihyperalgesic effects of the alpha(2)-adrenoceptor agonist medetomidine. Behavioral experiments showed a more intense antihyperalgesia in the phase of maintenance of inflammation than in the early or resolution stages. Maximum effect, without sedation, was observed with a dose of 40 microg/kg (66+/-12% and 76+/-15% reduction of mechanical and thermal hyperalgesia). No change was observed in the paw swelling, indicating that its effects were not secondary to a reduction of inflammation. In electrophysiological experiments, the effect was more pronounced in animals with an intact spinal cord than in spinalized animals (max. effects of 2+/-0.7% vs. 48+/-11% of control, noxious mechanical stimulation). We conclude that the antihyperalgesic effect of medetomidine depends on the time course of inflammation and that it is mainly located supraspinally.
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Affiliation(s)
- Carlos Molina
- Departamento de Fisiología, Facultad de Medicina, Campus Universitario, Universidad de Alcalá, Alcalá de Henares, 28871 Madrid, Spain
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21
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Ottani A, Leone S, Sandrini M, Ferrari A, Bertolini A. The analgesic activity of paracetamol is prevented by the blockade of cannabinoid CB1 receptors. Eur J Pharmacol 2006; 531:280-1. [PMID: 16438952 DOI: 10.1016/j.ejphar.2005.12.015] [Citation(s) in RCA: 161] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Accepted: 12/12/2005] [Indexed: 01/12/2023]
Abstract
The mechanism of the analgesic activity of paracetamol (acetaminophen), one of the most widely used drugs for the treatment of pain, is still not clear. Here we show that in rats, using the hot plate test, the analgesic effect of paracetamol is prevented by two antagonists at cannabinoid CB1 receptors (AM281 and SR141716A) at doses that prevent the analgesic activity of the cannabinoid CB1 agonist HU210. Our present results suggest that paracetamol-induced antinociception involves the cannabinoid system.
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Affiliation(s)
- Alessandra Ottani
- Department of Biomedical Sciences, Section of Pharmacology, University of Modena and Reggio Emilia, Via G. Campi 287, 41100 Modena, Italy
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22
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Pozzi A, Muir WW, Traverso F. Prevention of central sensitization and pain by N-methyl-D-aspartate receptor antagonists. J Am Vet Med Assoc 2006; 228:53-60. [PMID: 16426166 DOI: 10.2460/javma.228.1.53] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Antonio Pozzi
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, OH 43210, USA
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23
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Zakaria ZA, Safarul M, Valsala R, Sulaiman MR, Fatimah CA, Somchit MN, Mat Jais AM. The influences of temperature and naloxone on the antinociceptive activity of Corchorus olitorius L. in mice. Naunyn Schmiedebergs Arch Pharmacol 2005; 372:55-62. [PMID: 16133487 DOI: 10.1007/s00210-005-1089-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2004] [Accepted: 07/31/2005] [Indexed: 01/28/2023]
Abstract
A series of preliminary studies was carried out to evaluate the antinociceptive (pain relief) activity of the aqueous extract of Corchorus olitorius L. leaves (COAE) and to determine the influence of temperature and opioid receptors on COAE activity using the abdominal constriction and hot plate tests in mice. COAE, at concentrations of 10, 25, 50, 75, and 100%, showed both peripheral and central antinociception that are non-concentration- and concentration-dependent respectively. The peripheral activity was clearly observed at a concentration of 25% and diminished at a concentration of 100%, while the central activity was observed at all the concentrations of COAE used. Furthermore, the insignificant results obtained indicated that this peripheral activity (at concentrations of 25 and 50%) was comparable to that of morphine (0.8 mg/kg). Pre-heating COAE at a temperature of 80 degrees C and 100 degrees C, or 60 degrees C and 80 degrees C was found to enhance its peripheral and central antinociception respectively. Pre-treatment with naloxone (10 mg/kg), a general opioid receptor antagonist, for 5 min, followed by COAE, was found to completely block its peripheral, but not central, antinociceptive activity. Based on this observation, we conclude that the antinociceptive activity exhibited by C. olitorius is enhanced by the increase in temperature and may be mediated peripherally, but not centrally, at least in part, via an opioid receptor.
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Affiliation(s)
- Z A Zakaria
- School of Biotechnology and Life Sciences, Universiti Industri Selangor, Jalan Zirkon A7/A, Seksyen 7, 40000, Shah Alam, Selangor, Malaysia.
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Herrero JF, Romero-Sandoval EA, Gaitan G, Mazario J. Antinociception and the new COX inhibitors: research approaches and clinical perspectives. CNS DRUG REVIEWS 2003; 9:227-52. [PMID: 14530796 PMCID: PMC6741672 DOI: 10.1111/j.1527-3458.2003.tb00251.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
New generations of cyclooxygenase (COX) inhibitors are more potent and efficacious than their traditional parent compounds. They are also safer than the classic non-steroidal anti-inflammatory drugs (NSAIDs) and are starting to be used not only for low to moderate intensity pain, but also for high intensity pain. Three different strategies have been followed to improve the pharmacological profile of COX inhibitors: 1. Development of COX-2 selective inhibitors. This is based on the initial hypothesis that considered COX-2 as the enzyme responsible for the generation of prostaglandins only in inflammation, and, therefore, uniquely responsible for inflammation, pain and fever. Initial expectations gave rise to controversial results, still under discussion. The second generation of these compounds is being developed and should contribute to clarifying both their efficacy and the specific functions of the COX enzymes. 2. Modified non-selective COX inhibitors. Molecules like nitro-NSAIDs or tromethamine salt derivatives have been synthesized considering that both COX-1 and COX-2 are responsible for the synthesis of prostaglandins involved either in homeostatic functions or inflammation. Nitroaspirin, nitroparacetamol or dexketoprofen trometamol are some examples of molecules that are already showing an important clinical efficacy. The modifications performed in their structures seem to lower the unwanted side effects as well as to enhance their analgesic efficacy. 3. Combined therapy of classic NSAIDs with other drugs. This strategy looks for improvements in the incidence of adverse effects or to take advantage of the synergistic enhancement of their therapeutic effects. Some of the molecules resulting from these strategies are very valuable as therapeutic agents and open a wide range of possibilities in the treatment of high intensity pain, including neuropathic pain, and opiate sparing therapy.
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Affiliation(s)
- Juan F Herrero
- Departamento de Fisología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain.
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25
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Poveda R, Planas E, Pol O, Romero A, Sánchez S, Puig MM. Interaction between metamizol and tramadol in a model of acute visceral pain in rats. Eur J Pain 2003; 7:439-48. [PMID: 12935796 DOI: 10.1016/s1090-3801(03)00003-x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Tramadol (TRM) and metamizol (MTZ) are drugs with complex mechanisms of action, extensively used in combination in pain management. In the present investigation we have evaluated the interaction between MTZ:TRM in the ethacrinic acid writhing test in rats. Dose-response curves (s.c.) were obtained for each drug individually, combined in fixed potency ratios (1:0.3, 1:1, 1:3), and for MTZ in presence of a fixed-dose of TRM (3.5 mg/kg). Interactions were analysed using isobolograms, interaction indexes (INT-I) and ANOVA. We used naloxone (1 mg/kg s.c.) to determine the opioid-component of the effects (ED80). Isobolograms demonstrated antagonism at the ED20, for 1:0.3 and 1:3 mixtures (p<0.01), whereas 1:1 was additive. At the ED50 and ED80 all combinations showed synergy. Fixed-dose experiments demonstrated that treatment (p<0.0001), dose (p<0.0001), and their interaction (p<0.0001) were statistically significant. Naloxone partially antagonized TRM (67%), but not MTZ; the percentage reversal of the combinations was directly related to the dose of TRM in the combination. The results show that the MTZ:TRM interaction on antinociception is synergistic or antagonistic depending on the level of effect. Synergy is demonstrated at 50% or higher levels, thus supporting the results obtained in humans by our group. Below the ED50 antagonism or additivity is present depending on the ratio of the combination. The mechanisms of the interaction remain unknown.
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Affiliation(s)
- Raquel Poveda
- Department of Pharmacology, School of Odontology, University of Barcelona, Barcelona 08807, Spain
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26
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You HJ, Mørch CD, Chen J, Arendt-Nielsen L. Differential antinociceptive effects induced by a selective cyclooxygenase-2 inhibitor (SC-236) on dorsal horn neurons and spinal withdrawal reflexes in anesthetized spinal rats. Neuroscience 2003; 121:459-72. [PMID: 14522004 DOI: 10.1016/s0306-4522(03)00296-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The aim of present study was to examine the effect of a selective cyclooxygenase-2 (COX-2) inhibitor SC-236 (4 mg/kg) on the simultaneous responsiveness of spinal wide-dynamic range (WDR) neurons and single motor units (SMUs) from gastrocnemius soleus muscles to mechanical stimuli (pressure and pinch) and repeated suprathreshold (1.5xT, the intensity threshold) electrical stimuli with different frequencies (3 Hz, 20 Hz) under normal conditions and bee venom (BV, 0.2 mg/50 microl)-induced inflammation and central sensitization. During normal conditions, the responses of SMUs, but not WDR neurons, to mechanical and repeated electrical stimuli (3 Hz, wind-up) were depressed by systemic administration of SC-236 as well as its vehicle (100% dimethyl sulfoxide (DMSO)). The after-discharges of both the WDR neurons and the simultaneously recorded SMUs after electrical stimuli with 20 Hz were markedly depressed only by SC-236, indicating that the mechanisms underlying the generation of the C-fiber mediated late responses and the after-discharges may be different. The enhanced responsiveness of both WDR neurons and SMUs to mechanical pressure stimuli (allodynia) and pinch stimuli (hyperalgesia) in the BV experiments was apparently depressed by SC-236, but not its vehicle. For electrical stimulation, the enhanced late responses and after-discharges, but not early responses, of both the WDR neurons and the simultaneously recorded SMUs were markedly depressed only by SC-236. This indicates that different central pharmacological mechanisms underlie the generation of these enhanced early, late responses, and after-discharges during BV-induced inflammation. The data suggest that the COX-2 inhibitor SC-236 apparently depress the activities of both spinal cord dorsal horn neuron and spinal withdrawal reflex during BV-induced sensitization, indicating that COX-2 plays an important role in the maintenance of central sensitization.
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Affiliation(s)
- H J You
- Center for Sensory-Motor Interaction, Laboratory for Experimental Pain Research, Aalborg University, Fredrik Bajers Vej 7D-3, DK-9220, Aalborg, Denmark.
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27
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Alfonso Romero-Sandoval E, Del Soldato P, Herrero JF. The effects of sham and full spinalization on the antinociceptive effects of NCX-701 (nitroparacetamol) in monoarthritic rats. Neuropharmacology 2003; 45:412-9. [PMID: 12871658 DOI: 10.1016/s0028-3908(03)00193-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Nitric oxide (NO)-releasing NSAIDs have been shown to be safer and more potent as antinociceptive and anti-inflammatory agents than their parent compounds. NCX-701 (nitroparacetamol), in contrast to paracetamol, is an effective antinociceptive drug in normal animals but their effectiveness in monoarthritis has not been compared. We have now investigated this question by comparing the antinociceptive effects of i.v. NCX-701 and paracetamol in monoarthritic rats under alpha-chloralose anesthesia. The influence of spinalization on the effects of NCX-701 was also studied. NCX-701 and paracetamol were equipotent in reducing single motor unit responses to noxious mechanical stimulation, ID50s of 320+/-1.2 and 305+/-1.2 micromol/kg, respectively. The mechanism of action seems to be different since NCX-701, but not paracetamol, reduced wind-up. This effect suggests a central action, probably within the spinal cord. Sham spinalization reduced the effect of NCX-701 on nociceptive responses drastically. In spinalized animals, however, the effect was similar to that observed in intact animals, indicating a strong effect of NCX-701 at spinal sites, which counterbalances the decrease in the activity induced by the surgery. We conclude that NCX-701 is an effective antinociceptive drug in arthritic animals, with a mechanism of action located in the spinal cord, and different to that of paracetamol.
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Affiliation(s)
- E Alfonso Romero-Sandoval
- Departamento de Fisiología, Facultad de Medicina, Campus Universitario, Universidad de Alcalá, Alcalá de Henares, 28871, Madrid, Spain
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28
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Page GG, Ben-Eliyahu S. Indomethacin attenuates the immunosuppressive and tumor-promoting effects of surgery. THE JOURNAL OF PAIN 2002; 3:301-8. [PMID: 14622754 DOI: 10.1054/jpai.2002.125184] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
We have previously shown in rats that both intrathecal and systemic analgesia regimens attenuate surgery-induced increases in tumor susceptibility. The current study used indomethacin to assess the role of prostaglandins and inflammation-associated pain in mediating the deleterious effects of surgery on immunity and tumor susceptibility. Male and female Fischer 344 rats were anesthetized with halothane and were either subjected or not to experimental laparotomy, followed by the administration of indomethacin or vehicle. Tumor susceptibility was assessed by the lung retention assay using the syngeneic MADB106 mammary adenocarcinoma cell line, a natural killer (NK)-sensitive tumor that colonizes only in the lungs. Surgery resulted in a 2- to 3.5-fold increase in lung tumor retention, and indomethacin administration significantly reduced this effect in both sexes without affecting unoperated animals. Indomethacin also attenuated the reductions in rearing behavior evident after surgery, suggesting that it relieved abdominal discomfort. Surgery increased interleukin-6 levels and suppressed NK activity per milliliter blood. Indomethacin restored NK activity in both male and female rats but attenuated surgery-induced interleukin-6 increases only in the male rats. These findings further support our previous work implicating pain in mediating the tumor-enhancing effects of surgery and implicate prostaglandins in mediating this effect. If similar relationships occur in humans, controlling postoperative pain and inflammation must become a priority in the management of cancer patients undergoing surgery.
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Affiliation(s)
- Gayle G Page
- School of Nursing, Johns Hopkins University, Baltimore, MD 21205, USA.
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29
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Romero-Sandoval EA, Mazario J, Howat D, Herrero JF. NCX-701 (nitroparacetamol) is an effective antinociceptive agent in rat withdrawal reflexes and wind-up. Br J Pharmacol 2002; 135:1556-62. [PMID: 11906970 PMCID: PMC1573254 DOI: 10.1038/sj.bjp.0704589] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. Non-steroidal anti-inflammatory drugs (NSAIDs) are effective anti-inflammatory and analgesic drugs although they also induce unwanted side effects due to the inhibition of the physiological effects regulated by prostaglandins. This has led to the search for new compounds with fewer side effects, such as the nitro-NSAIDs (NO-NSAIDs). Paracetamol is an analgesic drug devoid of some of the side effect of the NSAIDs but without anti-inflammatory activity. NCX-701 is a nitric oxide releasing version of paracetamol with anti-inflammatory and analgesic properties. 2. We have tested, in the single motor unit technique, the antinociceptive actions of intravenous cumulative doses of NCX-701 vs paracetamol, studying their antinociceptive effects in responses to noxious mechanical and electrical stimulation (wind-up). 3. Paracetamol did not induce any significant effect at the doses tested (maximum of 480 micromol kg(-1), 72.5 mg kg(-1)). NCX-701 however was very effective in reducing responses to noxious mechanical stimulation (32+/-10% of control response) and wind-up (ED(50) of 147+/-1 micromol kg(-1), 41.5+/-0.3 mg kg(-1)). The inhibition was not reversed by 1 mg kg(-1) of the opioid antagonist naloxone. In control experiments performed with either the vehicle or the NO donor NOC-18, no significant changes were observed in the nociceptive responses studied. 4. We conclude that NCX-701 is a very effective non-opioid antinociceptive agent in normal animals and its action is located mainly at central areas. The antinociceptive effect was not due solely to the release of NO.
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Affiliation(s)
| | - Javier Mazario
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | | | - Juan F Herrero
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
- Author for correspondence:
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30
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Gaitán G, Herrero JF. Subeffective doses of dexketoprofen trometamol enhance the potency and duration of fentanyl antinociception. Br J Pharmacol 2002; 135:393-8. [PMID: 11815374 PMCID: PMC1573153 DOI: 10.1038/sj.bjp.0704491] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The combination of classic non-steroidal antiinflammatory drugs (NSAIDs) with opiates induces more analgesia than the summed effect of each drug given separately. No studies have been performed using new generation NSAIDs and fentanyl nor on the duration of this effect. We have studied the analgesic effect of fentanyl alone and after the administration of subeffective doses of dexketoprofen trometamol in rat nociceptive responses. The responses were evoked by noxious mechanical stimulation and were recorded as single motor units in male Wistar rats anaesthetized with alpha-chloralose. The effective dose 50 (ED(50)) observed with fentanyl was 22.4 +/- 1.5 microg kg(-1) and full recovery was apparent 20 min later. The administration of a total dose of 40 microg kg(-1) of dexketoprofen trometamol did not induce any significant effect on the nociceptive responses. In the presence of dexketoprofen trometamol, the ED(50) for fentanyl was 5 fold lower than before: 3.8 +/- 1.1 microg kg(-1) and no significant recovery was observed 45 min later. The opioid antagonist naloxone (200 microg kg(-1)) did not reverse the effect, although in control experiments the same dose was able to prevent any action of fentanyl given alone. We conclude that the combination of fentanyl and subeffective doses of dexketoprofen trometamol induces a more potent and longer lasting analgesic effect than that observed with fentanyl alone, and that this is not an opioid mediated action.
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Affiliation(s)
- Gema Gaitán
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
| | - Juan F Herrero
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
- Author for correspondence:
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França DS, Souza AL, Almeida KR, Dolabella SS, Martinelli C, Coelho MM. B vitamins induce an antinociceptive effect in the acetic acid and formaldehyde models of nociception in mice. Eur J Pharmacol 2001; 421:157-64. [PMID: 11516431 DOI: 10.1016/s0014-2999(01)01038-x] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
The effect of some B vitamins in chemical and thermal models of nociception in mice was investigated. The association thiamine/pyridoxine/cyanocobalamin (TPC, 20-200 mg/kg, i.p. or per os), thiamine, pyridoxine (50-200 mg/kg, i.p.) or riboflavin (3-100 mg/kg, i.p) induced an antinociceptive effect, not changed by naloxone (10 mg/kg, i.p.), in the acetic acid writhing model. Treatment for 7 days with thiamine/pyridoxine/cyanocobalamin (100 or 200 mg/kg, i.p.), thiamine (50 or 100 mg/kg) or pyridoxine (50 or 100 mg/kg) or acute treatment with riboflavin (6 or 12 mg/kg, i.p) inhibited the nociceptive response induced by formaldehyde. The B vitamins did not inhibit the nociceptive response in the hot-plate model. Both 7-day thiamine/pyridoxine/cyanocobalamin (100 mg/kg, i.p.) or acute riboflavin (25 or 50 mg/kg, i.p.) treatment partially reduced formaldehyde-induced hindpaw oedema. The B vitamins antinociceptive effect may involve inhibition of the synthesis and/or action of inflammatory mediators since it was not observed in the hot-plate model, was not reversed by naloxone, only the second phase of the formaldehyde-induced nociceptive response was inhibited, and formaldehyde-induced hindpaw oedema was reduced.
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Affiliation(s)
- D S França
- Laboratory of Pharmacology, Faculty of Pharmacy, Federal University of Minas Gerais, Avenida Olegário Maciel 2360, 30180-112 MG, Belo Horizonte, Brazil
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32
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Mazario J, Gaitan G, Herrero JF. Cyclooxygenase-1 vs. cyclooxygenase-2 inhibitors in the induction of antinociception in rodent withdrawal reflexes. Neuropharmacology 2001; 40:937-46. [PMID: 11378164 DOI: 10.1016/s0028-3908(01)00020-x] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Non-steroidal antiinflammatory drugs (NSAIDs) inhibit the cyclooxygenase (COX) enzyme and so they are effective analgesic, antiinflammatory and antipyretic drugs. The discovery of COX-2 led to the search for new NSAIDs with a selective action over this isoenzyme. The experiments performed to date have shown either more, less or no different efficacy of new COX-2 selective NSAIDs when compared to the non-selective inhibitors, probably because the comparison has not been performed under similar conditions. We have therefore compared the analgesic activity of six NSAIDs with different selectivity for the COX isoenzymes. The experiments were performed using the recording of spinal cord nociceptive reflexes in anaesthetised rats and in awake mice. The non-selective COX inhibitors, such as dexketoprofen trometamol, were effective in reducing nociceptive responses both in normal and monoarthritic rats (ED50s: 0.31 and 3.97 micromol/kg, respectively), and in mice with paw inflammation (12.5 micromol/kg, p < 0.01). The COX-1 selective inhibitor SC-58560 showed efficacy in normal rats (ED50: 0.8 micromol/kg) and in mice with paw inflammation (15 micromol/kg, p < 0.05), but not in monoarthritic rats. The COX-2 selective inhibitors celecoxib (105 micromol/kg) and rofecoxib (128 micromol/kg) however, were not effective in any of the groups studied. We conclude that inhibition of both COX isoenzymes is needed to achieve an effective analgesia in inflammation.
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Affiliation(s)
- J Mazario
- Departamento de Fisiología, Facultad de Medicina, Campus Universitario, Universidad de Alcalá, Alcala de Henares 28871, Madrid, Spain
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Abstract
The substantial increase in our collective knowledge of pain physiology and pharmacology over the past decade has had a significant effect on the practice of clinical veterinary medicine. An overview of the basic anatomical and physiologic components of nociceptive processing is presented, as well as a discussion of the sensitizing events that occur within the nervous system in acute and chronic pathologic pain states. The unique features of visceral and neuropathic pain are also outlined. With the goal of improving the success of our therapeutic interventions, the final section is devoted to the various classes of analgesic drugs and techniques, and how they are best incorporated into pain management strategies.
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Affiliation(s)
- L A Lamont
- Department of Veterinary Clinical Medicine, College of Veterinary Medicine, University of Illinois, Urbana, USA
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34
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Herrero JF, Laird JM, López-García JA. Wind-up of spinal cord neurones and pain sensation: much ado about something? Prog Neurobiol 2000; 61:169-203. [PMID: 10704997 DOI: 10.1016/s0301-0082(99)00051-9] [Citation(s) in RCA: 489] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Wind-up is a frequency-dependent increase in the excitability of spinal cord neurones, evoked by electrical stimulation of afferent C-fibres. Although it has been studied over the past thirty years, there are still uncertainties about its physiological meaning. Glutamate (NMDA) and tachykinin NK1 receptors are required to generate wind-up and therefore a positive modulation between these two receptor types has been suggested by some authors. However, most drugs capable of reducing the excitability of spinal cord neurones, including opioids and NSAIDs, can also reduce or even abolish wind-up. Thus, other theories involving synaptic efficacy, potassium channels, calcium channels, etc. have also been proposed for the generation of this phenomenon. Whatever the mechanisms involved in its generation, wind-up has been interpreted as a system for the amplification in the spinal cord of the nociceptive message that arrives from peripheral nociceptors connected to C-fibres. This probably reflects the physiological system activated in the spinal cord after an intense or persistent barrage of afferent nociceptive impulses. On the other hand, wind-up, central sensitisation and hyperalgesia are not the same phenomena, although they may share common properties. Wind-up can be an important tool to study the processing of nociceptive information in the spinal cord, and the central effects of drugs that modulate the nociceptive system. This paper reviews the physiological and pharmacological data on wind-up of spinal cord neurones, and the perceptual correlates of wind-up in human subjects, in the context of its possible relation to the triggering of hyperalgesic states, and also the multiple factors which contribute to the generation of wind-up.
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MESH Headings
- Afferent Pathways/physiology
- Analgesics/pharmacology
- Anesthetics, Local/pharmacology
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Cats
- Humans
- Hyperalgesia/physiopathology
- Inflammation
- Ion Transport/drug effects
- Models, Neurological
- Morphine/pharmacology
- Nerve Fibers/drug effects
- Nerve Fibers/physiology
- Nerve Tissue Proteins/drug effects
- Nerve Tissue Proteins/physiology
- Neuralgia/physiopathology
- Neuronal Plasticity/drug effects
- Neuronal Plasticity/physiology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Neuropeptides/physiology
- Nociceptors/physiology
- Pain/drug therapy
- Pain/physiopathology
- Receptors, Metabotropic Glutamate/drug effects
- Receptors, Metabotropic Glutamate/physiology
- Receptors, N-Methyl-D-Aspartate/drug effects
- Receptors, N-Methyl-D-Aspartate/physiology
- Receptors, Neurokinin-1/drug effects
- Receptors, Neurokinin-1/physiology
- Reflex/physiology
- Spinal Cord/cytology
- Spinal Cord/physiopathology
- Substance P/physiology
- Synaptic Transmission/drug effects
- Viscera/innervation
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Affiliation(s)
- J F Herrero
- Departamento de Fisiología, Edificio de Medicina, Campus Universitario, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid, Spain.
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Abstract
Metamizol has been considered as a peripherally acting non-steroidal antiinflammatory drug, though a central action is possible. The aim of the present study was to elucidate if metamizol induces antinociception in the single motor unit preparation, in normal rats versus rats with carrageenan-induced monoarthritis, and whether this action is produced at central and/or peripheral sites. Metamizol induced a potent antinociceptive effect in both groups of animals, though the effect on responses evoked by natural stimulation was stronger in hyperalgesic rats. Metamizol also depressed wind-up in a dose-dependent manner. We conclude that metamizol is a potent antinociceptive agent both in normal and hyperalgesic animals and that the effect was induced both at peripheral and central sites, at the level of the spinal cord.
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Affiliation(s)
- J Mazario
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Madrid, Spain
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36
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Solano R, Herrero JF. Response properties of hind limb single motor units in normal rats and after carrageenan-induced inflammation. Neuroscience 1999; 90:1393-402. [PMID: 10338306 DOI: 10.1016/s0306-4522(98)00549-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The properties of single motor units from hind limb muscles and the changes in situations of hyperalgesia are not known in detail. We have therefore characterized the properties of single motor units in normal Wistar male rats and in rats with carrageenan-induced inflammation, under alpha-chloralose anaesthesia. Units were studied from three different muscles: peroneus longus, tibialis anterior and extensor digitorum longus. The properties of single motor units were not homogeneous in the three muscles studied in normal animals, showing different sizes of cutaneous receptive fields, thresholds for natural and electrical stimulation, and encoding of responses at different intensities of stimulation. Intraplantar injections of carrageenan induced a significant inflammation of the paw and a change in spontaneous behaviour observed in open field experiments. After inflammation, the responses to cutaneous stimulation of the single motor units became more homogeneous. The threshold for mechanical stimulation was lower for peroneus longus and tibialis anterior but not for extensor digitorum longus units when compared to normal animals. The receptive fields were larger when mapped with a 500 mN von Frey hair but not when mapped using a threshold intensity hair. The threshold for thermal stimulation was lower after inflammation than in normal conditions in all cases, whereas the threshold for electrical stimulation was lower in tibialis anterior and extensor digitorum longus units. An enhancement of responses related to the increase of stimulus intensity was seen in normal animals in all muscles for mechanical and electrical stimuli (but not for thermal). After inflammation, a relationship between firing rate and intensity of stimulation was seen in all cases studied. The firing of single motor units showed over 50% adaptation in the normal condition and over 75% after inflammation when stimulated for 10 s at mechanical threshold intensity. After inflammation, the rate of adaptation was significantly lower when suprathreshold intensity was used for mechanical stimulation. No differences were seen in the adaptation of units to thermal stimulation. We conclude that, in situations of hyperalgesia due to inflammation, the threshold, encoding of stimulus intensity and adaptation of single motor units from different muscles changed, resulting in a narrower range of responses and a more homogeneous population of units.
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Affiliation(s)
- R Solano
- Departamento de Fisiología, Facultad de Medicina, Universidad de Alcalá, Alcalá de Henares, Madrid, Spain
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Mazario J, Roza C, Herrero JF. The NSAID dexketoprofen trometamol is as potent as mu-opioids in the depression of wind-up and spinal cord nociceptive reflexes in normal rats. Brain Res 1999; 816:512-7. [PMID: 9878876 DOI: 10.1016/s0006-8993(98)01203-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The aim of this study was to examine the potency of the antinociceptive effects of the non-steroidal antiinflammatory drug (NSAID), Dexketoprofen Trometamol (the active enantiomer of ketoprofen) on spinal cord nociceptive reflexes. These effects were compared with those of the mu-opioid receptor agonist fentanyl in normal animals. The experiments were performed in male Wistar rats anaesthetised with alpha-chloralose. The nociceptive reflexes were recorded as single motor units in peripheral muscles, activated by mechanical and electrical stimulation. Both dexketoprofen and fentanyl inhibited responses evoked by mechanical and electrical stimulation with doses in the same nanomolar range (dexketoprofen ID50s: 100 and 762 nmol kg-1 and fentanyl: 40 and 51 nmol kg-1, respectively). Dexketoprofen and fentanyl also significantly inhibited wind-up. Since fentanyl has been shown to be some 1000 times more potent than morphine in this type of experiments, we conclude that dexketoprofen has central analgesic actions in normal animals and depresses nociceptive responses with a potency similar to that of mu-opioid agonists.
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Affiliation(s)
- J Mazario
- Departamento de Fisiología, Facultad de Medicina, Campus Universitario, Universidad de Alcalá, Alcalá de Henares, 28871, Madrid, Spain
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38
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McClean M, Chizh BA, Headley PM. Effects of NMDA receptor antagonists on nociceptive responses in vivo: comparison of antagonists acting at the glycine site with uncompetitive antagonists. Amino Acids 1999; 14:217-21. [PMID: 9871464 DOI: 10.1007/bf01345265] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
We have shown that members of a new series of tricyclic pyridophthalazine diones, defined as glycineB site NMDA antagonists in vitro, are selective and systemically active NMDA antagonists in vivo. In electrophysiological tests in alpha-chloralose anaesthetised rats, these compounds reduced nociceptive reflex responses. In conscious rats they displayed analgesic properties. These glycineB antagonists were compared electrophysiologically with several uncompetitive NMDA channel blockers. The degree of voltage dependence previously reported in vitro related to the effectiveness of the agents against different amplitude nociceptive responses of spinal cord neurones in vivo.
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Affiliation(s)
- M McClean
- University of Bristol, Department of Physiology, School of Medical Sciences, United Kingdom
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39
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Abstract
Non-steroidal anti-inflammatory drugs inhibit constitutive (COX-1) and induced cyclooxygenase (COX-2), blocking prostaglandin production. We have compared the effects on nociceptive reflexes of meloxicam, which is COX-2 selective, with indomethacin, which is non-selective, using an in vitro spinal cord preparation. Cords were taken from naive rats, and from rats with carrageenan-induced hyperalgesia of one hindpaw. Reflex thresholds were lower in carrageenan preparations. Superfusion with meloxicam (10-100 microM) dose-dependently inhibited baseline reflexes and wind-up in normal and carrageenan preparations, whereas indomethacin (100-300 microM) had no effect. Thus meloxicam inhibits spinal reflexes, whereas indomethacin does not, despite its high affinity for both COX isoforms. We conclude that meloxicam has spinal antinociceptive actions which cannot be explained by the current concept of COX inhibition.
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Affiliation(s)
- J A Lopez-Garcia
- Department of Physiology, School of Medicine, University of Alcalá, Alcalá de Henares, Madrid, Spain
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Herrero JF, Parrado A, Cervero F. Central and peripheral actions of the NSAID ketoprofen on spinal cord nociceptive reflexes. Neuropharmacology 1997; 36:1425-31. [PMID: 9423930 DOI: 10.1016/s0028-3908(97)00120-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Ketoprofen is a non-steroidal antiinflammatory drug (NSAID) which provides effective analgesia in situations of pain provoked by tissue inflammation. However, the location of its analgesic effects, (peripheral tissues versus central nervous system), have not been clearly identified and separated. In the present study the effectiveness of ketoprofen was examined in two different types of experiments: (i) Open field behavioural tests in conscious rats, and (ii) spinal cord nociceptive reflexes (single motor units) activated by electrical and thermal stimulation in chloralose anaesthetised rats. The experiments were performed in rats with carrageenan-induced inflammation of one hindpaw, or of one knee joint. The administration of ketoprofen significantly inhibited the reduction of exploratory movements caused by inflammation in open field experiments. Ketoprofen was also effective in depressing reflex activity evoked by electrical and noxious thermal stimulation of the skin, either in inflamed tissue or in normal tissue of monoarthritic animals. It was also effective in the reduction of reflex wind-up; a phenomenon in which the activity of spinal cord neurones increases progressively with high frequency electrical stimulation. We therefore conclude that ketoprofen has central as well as peripheral analgesic activity.
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Affiliation(s)
- J F Herrero
- Department of Physiology, Faculty of Medicine, University of Alcalá, Madrid, Spain.
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Bradley KJ, Headley PM. Effect of agmatine on spinal nociceptive reflexes: lack of interaction with alpha2-adrenoceptor or mu-opioid receptor mechanisms. Eur J Pharmacol 1997; 331:133-8. [PMID: 9274971 DOI: 10.1016/s0014-2999(97)01043-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Agmatine has been tested i.v. in alpha-chloralose anaesthetised rats for its effects on spinal nociceptive reflexes evoked by mechanical and electrical stimuli. Agmatine did not affect reflexes until very high doses (200 mg/kg, i.v.) which also caused complex cardiovascular disturbances. In spinally intact rats agmatine reduced reflexes; it was slightly less potent when there was carrageenan-induced hind paw inflammation. The alpha2-adrenoceptor antagonist atipamezole (80 microg/kg) did not significantly affect these reductions. In spinalised animals, agmatine caused a generalised increase in background firing which in animals with a non-inflamed paw was significantly reduced after atipamezole. There was no significant change in evoked responses once corrected for background activity. In all groups of animals agmatine, when administered at various doses and times prior to the mu-opioid receptor agonist fentanyl, had no effect on the ID50 of fentanyl.
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MESH Headings
- Adrenergic alpha-Antagonists/pharmacology
- Agmatine/pharmacology
- Analgesics, Opioid/pharmacology
- Animals
- Blood Pressure/drug effects
- Electric Stimulation
- Fentanyl/pharmacology
- Hindlimb/innervation
- Male
- Motor Neurons/drug effects
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/innervation
- Nociceptors/drug effects
- Physical Stimulation
- Rats
- Rats, Wistar
- Receptors, Adrenergic, alpha-2/drug effects
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/drug effects
- Reflex/drug effects
- Spinal Cord/drug effects
- Spinal Cord/physiology
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Affiliation(s)
- K J Bradley
- Department of Physiology, School of Medical Sciences, University Walk, Bristol, UK
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