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Costa AR, Tavares I, Martins I. How do opioids control pain circuits in the brainstem during opioid-induced disorders and in chronic pain? Implications for the treatment of chronic pain. Pain 2024; 165:324-336. [PMID: 37578500 DOI: 10.1097/j.pain.0000000000003026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 07/07/2023] [Indexed: 08/15/2023]
Abstract
ABSTRACT Brainstem areas involved in descending pain modulation are crucial for the analgesic actions of opioids. However, the role of opioids in these areas during tolerance, opioid-induced hyperalgesia (OIH), and in chronic pain settings remains underappreciated. We conducted a revision of the recent studies performed in the main brainstem areas devoted to descending pain modulation with a special focus on the medullary dorsal reticular nucleus (DRt), as a distinctive pain facilitatory area and a key player in the diffuse noxious inhibitory control paradigm. We show that maladaptive processes within the signaling of the µ-opioid receptor (MOR), which entail desensitization and a switch to excitatory signaling, occur in the brainstem, contributing to tolerance and OIH. In the context of chronic pain, the alterations found are complex and depend on the area and model of chronic pain. For example, the downregulation of MOR and δ-opioid receptor (DOR) in some areas, including the DRt, during neuropathic pain likely contributes to the inefficacy of opioids. However, the upregulation of MOR and DOR, at the rostral ventromedial medulla, in inflammatory pain models, suggests therapeutic avenues to explore. Mechanistically, the rationale for the diversity and complexity of alterations in the brainstem is likely provided by the alternative splicing of opioid receptors and the heteromerization of MOR. In conclusion, this review emphasizes how important it is to consider the effects of opioids at these circuits when using opioids for the treatment of chronic pain and for the development of safer and effective opioids.
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Affiliation(s)
- Ana Rita Costa
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
| | - Isaura Tavares
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
| | - Isabel Martins
- Department of Biomedicine, Unit of Experimental Biology, Faculty of Medicine, University of Porto, Porto, Portugal
- IBMC-Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- I3S- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal. Costa is now with the Department of Biochemistry and Biophysics, Stockholm University, Stockholm, Sweden and Science for Life Laboratory, Solna, Sweden
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Coutens B, Ingram SL. Key differences in regulation of opioid receptors localized to presynaptic terminals compared to somas: Relevance for novel therapeutics. Neuropharmacology 2023; 226:109408. [PMID: 36584882 PMCID: PMC9898207 DOI: 10.1016/j.neuropharm.2022.109408] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 12/05/2022] [Accepted: 12/27/2022] [Indexed: 12/29/2022]
Abstract
Opioid receptors are G protein-coupled receptors (GPCRs) that regulate activity within peripheral, subcortical and cortical circuits involved in pain, reward, and aversion processing. Opioid receptors are expressed in both presynaptic terminals where they inhibit neurotransmitter release and postsynaptic locations where they act to hyperpolarize neurons and reduce activity. Agonist activation of postsynaptic receptors at the plasma membrane signal via ion channels or cytoplasmic second messengers. Agonist binding initiates regulatory processes that include phosphorylation by G protein receptor kinases (GRKs) and recruitment of beta-arrestins that desensitize and internalize the receptors. Opioid receptors also couple to effectors from endosomes activating intracellular enzymes and kinases. In contrast to postsynaptic opioid receptors, receptors localized to presynaptic terminals are resistant to desensitization such that there is no loss of signaling in the continuous presence of opioids over the same time scale. Thus, the balance of opioid signaling in circuits expressing pre- and postsynaptic opioid receptors is shifted toward inhibition of presynaptic neurotransmitter release during continuous opioid exposure. The functional implication of this shift is not often acknowledged in behavioral studies. This review covers what is currently understood about regulation of opioid/nociceptin receptors, with an emphasis on opioid receptor signaling in pain and reward circuits. Importantly, the review covers regulation of presynaptic receptors and the critical gaps in understanding this area, as well as the opportunities to further understand opioid signaling in brain circuits. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".
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Affiliation(s)
- Basile Coutens
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA
| | - Susan L Ingram
- Department of Anesthesiology, University of Colorado Anschutz Medical Campus, Aurora, CO, 80045, USA.
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Reeves KC, Shah N, Muñoz B, Atwood BK. Opioid Receptor-Mediated Regulation of Neurotransmission in the Brain. Front Mol Neurosci 2022; 15:919773. [PMID: 35782382 PMCID: PMC9242007 DOI: 10.3389/fnmol.2022.919773] [Citation(s) in RCA: 42] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 05/26/2022] [Indexed: 12/15/2022] Open
Abstract
Opioids mediate their effects via opioid receptors: mu, delta, and kappa. At the neuronal level, opioid receptors are generally inhibitory, presynaptically reducing neurotransmitter release and postsynaptically hyperpolarizing neurons. However, opioid receptor-mediated regulation of neuronal function and synaptic transmission is not uniform in expression pattern and mechanism across the brain. The localization of receptors within specific cell types and neurocircuits determine the effects that endogenous and exogenous opioids have on brain function. In this review we will explore the similarities and differences in opioid receptor-mediated regulation of neurotransmission across different brain regions. We discuss how future studies can consider potential cell-type, regional, and neural pathway-specific effects of opioid receptors in order to better understand how opioid receptors modulate brain function.
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Affiliation(s)
- Kaitlin C. Reeves
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Department of Neuroscience, Charleston Alcohol Research Center, Medical University of South Carolina, Charleston, SC, United States
| | - Nikhil Shah
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Medical Scientist Training Program, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Braulio Muñoz
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
| | - Brady K. Atwood
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN, United States
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, IN, United States
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Tavares I, Costa-Pereira JT, Martins I. Monoaminergic and Opioidergic Modulation of Brainstem Circuits: New Insights Into the Clinical Challenges of Pain Treatment? FRONTIERS IN PAIN RESEARCH 2021; 2:696515. [PMID: 35295506 PMCID: PMC8915776 DOI: 10.3389/fpain.2021.696515] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Accepted: 06/08/2021] [Indexed: 12/22/2022] Open
Abstract
The treatment of neuropathic pain remains a clinical challenge. Analgesic drugs and antidepressants are frequently ineffective, and opioids may induce side effects, including hyperalgesia. Recent results on brainstem pain modulatory circuits may explain those clinical challenges. The dual action of noradrenergic (NA) modulation was demonstrated in animal models of neuropathic pain. Besides the well-established antinociception due to spinal effects, the NA system may induce pronociception by directly acting on brainstem pain modulatory circuits, namely, at the locus coeruleus (LC) and medullary dorsal reticular nucleus (DRt). The serotoninergic system also has a dual action depending on the targeted spinal receptor, with an exacerbated activity of the excitatory 5-hydroxytryptamine 3 (5-HT3) receptors in neuropathic pain models. Opioids are involved in the modulation of descending modulatory circuits. During neuropathic pain, the opioidergic modulation of brainstem pain control areas is altered, with the release of enhanced local opioids along with reduced expression and desensitization of μ-opioid receptors (MOR). In the DRt, the installation of neuropathic pain increases the levels of enkephalins (ENKs) and induces desensitization of MOR, which may enhance descending facilitation (DF) from the DRt and impact the efficacy of exogenous opioids. On the whole, the data discussed in this review indicate the high plasticity of brainstem pain control circuits involving monoaminergic and opioidergic control. The data from studies of these neurochemical systems in neuropathic models indicate the importance of designing drugs that target multiple neurochemical systems, namely, maximizing the antinociceptive effects of antidepressants that inhibit the reuptake of serotonin and noradrenaline and preventing desensitization and tolerance of MOR at the brainstem.
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Affiliation(s)
- Isaura Tavares
- Unit of Experimental Biology, Department of Biomedicine, Faculty of Medicine, University of Porto, Porto, Portugal
- Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal
- *Correspondence: Isaura Tavares
| | - José Tiago Costa-Pereira
- Unit of Experimental Biology, Department of Biomedicine, Faculty of Medicine, University of Porto, Porto, Portugal
- Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal
- Faculty of Nutrition and Food Science, University of Porto, Porto, Portugal
| | - Isabel Martins
- Unit of Experimental Biology, Department of Biomedicine, Faculty of Medicine, University of Porto, Porto, Portugal
- Institute of Molecular and Cell Biology, University of Porto, Porto, Portugal
- Institute of Investigation and Innovation in Health, University of Porto, Porto, Portugal
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5
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Bagley EE, Ingram SL. Endogenous opioid peptides in the descending pain modulatory circuit. Neuropharmacology 2020; 173:108131. [PMID: 32422213 DOI: 10.1016/j.neuropharm.2020.108131] [Citation(s) in RCA: 70] [Impact Index Per Article: 17.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 05/01/2020] [Accepted: 05/04/2020] [Indexed: 02/07/2023]
Abstract
The opioid epidemic has led to a serious examination of the use of opioids for the treatment of pain. Opioid drugs are effective due to the expression of opioid receptors throughout the body. These receptors respond to endogenous opioid peptides that are expressed as polypeptide hormones that are processed by proteolytic cleavage. Endogenous opioids are expressed throughout the peripheral and central nervous system and regulate many different neuronal circuits and functions. One of the key functions of endogenous opioid peptides is to modulate our responses to pain. This review will focus on the descending pain modulatory circuit which consists of the ventrolateral periaqueductal gray (PAG) projections to the rostral ventromedial medulla (RVM). RVM projections modulate incoming nociceptive afferents at the level of the spinal cord. Stimulation within either the PAG or RVM results in analgesia and this circuit has been studied in detail in terms of the actions of exogenous opioids, such as morphine and fentanyl. Further emphasis on understanding the complex regulation of endogenous opioids will help to make rational decisions with regard to the use of opioids for pain. We also include a discussion of the actions of endogenous opioids in the amygdala, an upstream brain structure that has reciprocal connections to the PAG that contribute to the brain's response to pain.
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Affiliation(s)
- Elena E Bagley
- Discipline of Pharmacology and Charles Perkins Centre, University of Sydney, NSW, 2006, Australia
| | - Susan L Ingram
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, 97239, USA.
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A bifunctional-biased mu-opioid agonist-neuropeptide FF receptor antagonist as analgesic with improved acute and chronic side effects. Pain 2019; 159:1705-1718. [PMID: 29708942 DOI: 10.1097/j.pain.0000000000001262] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Opioid analgesics, such as morphine, oxycodone, and fentanyl, are the cornerstones for treating moderate to severe pain. However, on chronic administration, their efficiency is limited by prominent side effects such as analgesic tolerance and dependence liability. Neuropeptide FF (NPFF) and its receptors (NPFF1R and NPFF2R) are recognized as an important pronociceptive system involved in opioid-induced hyperalgesia and analgesic tolerance. In this article, we report the design of multitarget peptidomimetic compounds that show high-affinity binding to the mu-opioid receptor (MOPr) and NPFFRs. In vitro characterization of these compounds led to identification of KGFF03 and KGFF09 as G-protein-biased MOPr agonists with full agonist or antagonist activity at NPFFRs, respectively. In agreement with their biased MOPr agonism, KGFF03/09 showed reduced respiratory depression in mice, as compared to the unbiased parent opioid agonist KGOP01. Chronic subcutaneous administration of KGOP01 and KGFF03 in mice rapidly induced hyperalgesia and analgesic tolerance, effects that were not observed on chronic treatment with KGFF09. This favorable profile was further confirmed in a model of persistent inflammatory pain. In addition, we showed that KGFF09 induced less physical dependence compared with KGOP01 and KGFF03. Altogether, our data establish that combining, within a single molecule, the G-protein-biased MOPr agonism and NPFFR antagonism have beneficial effects on both acute and chronic side effects of conventional opioid analgesics. This strategy can lead to the development of novel and potent antinociceptive drugs with limited side effects on acute and chronic administration.
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7
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Weinbroum AA. Postoperative hyperalgesia—A clinically applicable narrative review. Pharmacol Res 2017; 120:188-205. [DOI: 10.1016/j.phrs.2017.02.012] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2016] [Revised: 02/08/2017] [Accepted: 02/08/2017] [Indexed: 02/08/2023]
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8
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Effects of combined opioids on pain and mood in mammals. PAIN RESEARCH AND TREATMENT 2012; 2012:145965. [PMID: 22550575 PMCID: PMC3324919 DOI: 10.1155/2012/145965] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 01/02/2012] [Indexed: 11/22/2022]
Abstract
The authors review the opioid literature for evidence of increased analgesia and reduced adverse side effects by combining mu-opioid-receptor (MOR) agonists, kappa-opioid-receptor (KOR) agonists, and nonselective low-dose-opioid antagonists (LD-Ant). We tested fentanyl (MOR agonist) and spiradoline (KOR agonist), singly and combined, against somatic and visceral pain models. Combined agonists induced additive analgesia in somatic pain and synergistic analgesia in visceral pain. Other investigators report similar effects and reduced tolerance and dependence with combined MOR agonist and KOR agonist. LD-Ant added to either a MOR agonist or KOR agonist markedly enhanced analgesia of either agonist. In accordance with other place-conditioning (PC) studies, our PC investigations showed fentanyl-induced place preference (CPP) and spiradoline-induced place aversion (CPA). We reduced fentanyl CPP with a low dose of spiradoline and reduced spiradoline CPA with a low dose of fentanyl. We propose combined MOR agonist, KOR agonist, and LD-Ant to produce superior analgesia with reduced adverse side effects, particularly for visceral pain.
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9
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Wang H, Akbar M, Weinsheimer N, Gantz S, Schiltenwolf M. Longitudinal observation of changes in pain sensitivity during opioid tapering in patients with chronic low-back pain. PAIN MEDICINE 2011; 12:1720-6. [PMID: 22082225 DOI: 10.1111/j.1526-4637.2011.01276.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Several studies have shown that exposure to opioids for short or long periods alters pain sensitivity. Little is known about changes in pain sensitivity during and after tapering of long-term prescribed opioid treatment in chronic low-back pain (cLBP) patients. DESIGN The goal of this prospective longitudinal study was to investigate pain sensitivity in a homogeneous patient population (cLBP patients only) after tapering of long-term (17 months) opioid use and to monitor the changes in pain sensitivity for 6 months. METHODS Pain sensitivity (thermal sensation and thermal pain thresholds in low back and nondominant hand) was measured by quantitative sensory testing (QST) at 1 day before (T1), 3 weeks after (T2), and 6 months after the start of opioid tapering (T3) in 35 patients with both cLBP and opioid medication (OP), 35 opioid-naïve cLBP patients (ON), and 28 individuals with neither pain nor opioid intake (HC). RESULTS Significant differences in heat pain thresholds were found among the three groups at all three time points (T1: P=0.001, T2: P=0.015, T3: P=0.008), but not between the two patient groups. OP patients showed lower cold pain thresholds at T2 than ON patients and HC. At T3, the heat pain thresholds of OP patients still remained lower than HC (P=0.017), while those of ON patients were normalized. CONCLUSIONS Our findings suggest that long-term use of opioids does not reduce pain sensitivity in cLBP patients; opioid tapering may induce brief hyperalgesia that can be normalized over a longer period.
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Affiliation(s)
- Haili Wang
- Department of Orthopedics, Trauma Surgery and Paraplegiology, University Hospital of Heidelberg, Heidelberg, Germany.
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10
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Akbari E. The role of cyclo-oxygenase inhibitors in attenuating opioid-induced tolerance, hyperalgesia, and dependence. Med Hypotheses 2011; 78:102-6. [PMID: 22047988 DOI: 10.1016/j.mehy.2011.10.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2011] [Revised: 08/21/2011] [Accepted: 10/04/2011] [Indexed: 11/28/2022]
Abstract
There is no denying that opioids are the most important analgesic drugs which are widely used in clinical situations. Still, prolonged administration of these drugs can cause to reduce their analgesic efficacy due to the development of tolerance. These drugs can also cause induction of hyperalgesia. In addition, long-term administration of opioids through reinforcing- and rewarding pathways of limbic system can result in expression of opioid dependence with the unintended consequences of opioid abuse/misuse and finally opioid addiction. As studies show, over-activity in cyclo-oxygenase pathways and production of prostaglandins due to long-term exposures of opioid have a critical role in the development of tolerance to antinociceptive effect of opioid, hyperalgesia, and opioid dependence. The present study aims at suggesting the hypothesis that through blending a non-steroid anti-inflammatory drug with opioid actively causes reduction in unwanted effects of opioid i.e. by inhibition of opioid-induced cyclo-oxygenase overactivity whereas it is well-known that the combination therapy via reducing opioid dosage reduces the unwanted effects.
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Affiliation(s)
- Esmaeil Akbari
- Department of Physiology, Molecular and Cell Biology Research Center, School of Medicine, Mazandaran University of Medical Sciences, Sari, Iran.
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11
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Abstract
Opioids are the most potent drugs for treatment of acute and chronic pain. However, accumulating evidence suggests that opioids may paradoxically also enhance pain, often referred to as opioid-induced hyperalgesia. Opioid-induced hyperalgesia is defined as an increased sensitivity to pain or a decreased pain threshold in response to opioid therapy. Several mechanisms have been proposed to support opioid-induced hyperalgesia. However, it remains unclear whether opioid-induced hyperalgesia develops during continuous chronic application of opioids or on their withdrawal. This review provides a comprehensive summary of clinical research concerning opioid-induced hyperalgesia and the molecular mechanisms of opioid withdrawal and opioid tolerance and other potential mechanisms which might induce hyperalgesia during opioid therapy will be discussed. The status quo of our knowledge will be summarized and the clinical relevance of opioid-induced hyperalgesia will be discussed.
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Affiliation(s)
- C Zöllner
- Klinik und Poliklinik für Anästhesiologie, Zentrum für Anästhesiologie und Intensivmedizin, Universitätsklinikum Hamburg Eppendorf, Martinistr. 52, 20246 Hamburg, Deutschland.
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12
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Van Bockstaele EJ, Reyes BAS, Valentino RJ. The locus coeruleus: A key nucleus where stress and opioids intersect to mediate vulnerability to opiate abuse. Brain Res 2010; 1314:162-74. [PMID: 19765557 PMCID: PMC3274960 DOI: 10.1016/j.brainres.2009.09.036] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 08/19/2009] [Accepted: 09/10/2009] [Indexed: 12/29/2022]
Abstract
The interaction between the stress axis and endogenous opioid systems has gained substantial clinical attention as it is increasingly recognized that stress predisposes to opiate abuse. For example, stress has been implicated as a risk factor in vulnerability to the initiation and maintenance of opiate abuse and is thought to play an important role in relapse in subjects with a history of abuse. Numerous reports indicating that stress alters individual sensitivity to opiates suggest that prior stress can influence the pharmacodynamics of opiates that are used in clinical settings. Conversely, the effects of opiates on different components of the stress axis can impact on individual responsivity to stressors and potentially predispose individuals to stress-related psychiatric disorders. One site at which opiates and stress substrates may interact to have global effects on behavior is within the locus coeruleus (LC), the major brain norepinephrine (NE)-containing nucleus. This review summarizes our current knowledge regarding the anatomical and neurochemical afferent regulation of the LC. It then presents physiological studies demonstrating opposing interactions between opioids and stress-related neuropeptides in the LC and summarizes results showing that chronic morphine exposure sensitizes the LC-NE system to corticotropin releasing factor and stress. Finally, new evidence for novel presynaptic actions of kappa-opioids on LC afferents is provided that adds another dimension to our model of how this central NE system is co-regulated by opioids and stress-related peptides.
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Affiliation(s)
- E J Van Bockstaele
- Department of Neurosurgery, Thomas Jefferson University, Farber Institute for Neurosciences, 900 Walnut Street, Suite 400, Philadelphia, PA 19107, USA.
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13
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Antinociceptive interactions of mu- and kappa-opioid agonists in the colorectal distension assay in rats. Pharmacol Biochem Behav 2009; 92:343-50. [DOI: 10.1016/j.pbb.2008.12.023] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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14
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Inhibitory effect of low-dose pentazocine on the development of antinociceptive tolerance to morphine. J Anesth 2009; 23:99-107. [DOI: 10.1007/s00540-008-0697-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2008] [Accepted: 09/22/2008] [Indexed: 10/21/2022]
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15
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Shu H, Hayashida M, Huang W, An K, Chiba S, Hanaoka K, Arita H. The comparison of effects of processed Aconiti tuber, U50488H and MK-801 on the antinociceptive tolerance to morphine. JOURNAL OF ETHNOPHARMACOLOGY 2008; 117:158-165. [PMID: 18328652 DOI: 10.1016/j.jep.2008.01.029] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2007] [Revised: 12/17/2007] [Accepted: 01/26/2008] [Indexed: 05/26/2023]
Abstract
In the previous studies, we demonstrated that an oriental herbal medicine, processed Aconiti tuber (PAT), at subanalgesic doses could inhibit or reverse the antinociceptive tolerance to morphine. In the present study, we compared the effect of PAT, trans-(+/-)-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidin)cyclohexyl)-benzeneacetamide methane sulfonate hydrate (U50488H), a selective kappa opioid receptor (KOR) agonist, and (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine-maleate (MK-801), a N-methyl-D-aspartate (NMDA) receptor antagonist, on the antinociceptive tolerance to morphine in the same experimental condition. Mice received subcutaneous morphine (10 mg/kg), and oral PAT at a subanalgesic dose (0.3 g/kg for mechanical or 1.0 g/kg for thermal test), or intraperitoneal U50488H at a subanalgesic dose (3 mg/kg), or MK-801 at a subanalgesic dose (0.1 mg/kg) once daily for 14 days. The mechanical nociceptive threshold was measured before, and at 60 min by tail pressure testing, and thermal nociceptive latency was measured before, and at 30 min by hot plate testing, after daily morphine injections. PAT and U50488H could not only inhibit the development of morphine tolerance but also reverse the already-developed morphine tolerance, while MK-801 could only inhibit the development of morphine tolerance but not reverse the already-developed morphine tolerance, in both mechanical and thermal nociceptive tests. These data suggested that PAT, an indirect-acting KOR agonist, share the common pharmacological property of KOR agonists on morphine tolerance, and that PAT may be superior to some NMDA receptor antagonists which do not reverse already-developed morphine tolerance.
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Affiliation(s)
- Haihua Shu
- Department of Anesthesiology, First Affiliated Hospital of Sun Yat-Sen University, 58# Zhongshan 2nd Road, Guangzhou, 510080, PR China.
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16
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Zöllner C, Schäfer M. [Remifentanil-based intraoperative anaesthesia and postoperative pain therapy. Is there an optimal treatment strategy?]. Anaesthesist 2008; 56:1038-46. [PMID: 17762929 DOI: 10.1007/s00101-007-1246-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Remifentanil is a synthetic opioid derivate with an agonist activity at mu-opioid receptors. The pharmacokinetic profile differs from other synthetic opioids. Remifentanil is rapidly metabolised by unspecific blood and tissue esterases and the metabolites have almost no intrinsic activity. According to its unique pharmacokinetic profile, remifentanil-based anaesthesia might be associated with a high level of postoperative pain, therefore, an appropriate postoperative pain management is an import aspect. In addition, remifentanil withdrawal induces a compensatory up-regulation of secondary messenger pathways, inducing hyperalgesia. This review provides a comprehensive summary of basic and clinical research concerning the intraoperative use of remifentanil and postoperative pain therapy. The relative contribution of rapid degradation and withdrawal-induced hyperalgesia to postoperative pain will be discussed. In addition, this review attempts to identify potential clinical implications and treatment strategies.
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Affiliation(s)
- C Zöllner
- Klinik für Anaesthesiologie und operative Intensivmedizin, Charité - Universitätsmedizin Berlin, Campus Benjamin Franklin, Berlin.
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17
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Tallent MK. Presynaptic inhibition of glutamate release by neuropeptides: use-dependent synaptic modification. Results Probl Cell Differ 2007; 44:177-200. [PMID: 17554500 DOI: 10.1007/400_2007_037] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Neuropeptides are signaling molecules that interact with G-protein coupled receptors located both pre- and postsynaptically. Presynaptically, these receptors are localized in axons and terminals away from presynaptic specializations. Neuropeptides are stored in dense core vesicles that are distinct from the clear synaptic vesicles containing classic neurotransmitters such as glutamate and GABA. Because they require a stronger Ca(2+) signal than synaptic vesicles, dense core vesicles do not release neuropeptides with single action potentials but rather require high-frequency trains. Thus, neuropeptides only modulate strongly stimulated synapses, providing negative or positive feedback. Many neuropeptides have been found to inhibit glutamate release from presynaptic terminals, and the major mechanism is likely direct interaction of betagamma G-protein subunits with presynaptic proteins such as SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor). The use of mouse genetic models and specific receptor antagonists are beginning to unravel the function of inhibitory neuropeptides. The opioid receptors kappa and mu, which are activated by endogenous opioid peptides such as dynorphin, enkephalin, and possibly the endomorphins, are important in modulating pain transmission. Dynorphin, nociceptin/orphanin FQ, and somatostatin and its related peptide cortistatin appear to play a role in modulation of learning and memory. Neuropeptide Y has important functions in ingestive behavior and also in entraining circadian rhythms. The existence of neuropeptides greatly expands the computational ability of the brain by providing additional levels of modulation.
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Affiliation(s)
- Melanie K Tallent
- Department of Pharmacology and Physiology, Philadelphia, PA 19102, USA.
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18
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19
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Koppert W, Schmelz M. The impact of opioid-induced hyperalgesia for postoperative pain. Best Pract Res Clin Anaesthesiol 2007; 21:65-83. [PMID: 17489220 DOI: 10.1016/j.bpa.2006.12.004] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Clinical evidence suggests that--besides their well known analgesic activity - opioids can increase rather than decrease sensitivity to noxious stimuli. Based on the observation that opioids can activate pain inhibitory and pain facilitatory systems, this pain hypersensitivity has been attributed to a relative predominance of pronociceptive mechanisms. Acute receptor desensitization via uncoupling of the receptor from G-proteins, upregulation of the cAMP pathway, activation of the N-methyl-D-aspartate (NMDA)-receptor system, as well as descending facilitation, have been proposed as potential mechanisms underlying opioid-induced hyperalgesia. Numerous reports exist demonstrating that opioid-induced hyperalgesia is observed both in animal and human experimental models. Brief exposures to micro-receptor agonists induce long-lasting hyperalgesic effects for days in rodents, and also in humans large-doses of intraoperative micro-receptor agonists were found to increase postoperative pain and morphine consumption. Furthermore, the prolonged use of opioids in patients is often associated with a requirement for increasing doses and the development of abnormal pain. Successful strategies that may decrease or prevent opioid-induced hyperalgesia include the concomitant administration of drugs like NMDA-antagonists, alpha2-agonists, or non-steroidal anti-inflammatory drugs (NSAIDs), opioid rotation or combinations of opioids with different receptor/selectivity.
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Affiliation(s)
- Wolfgang Koppert
- Klinik für Anästhesiologie, Universitätsklinikum Erlangen, Krankenhousstrasse 12, D-91054 Erlongen, Germany.
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20
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Winkler CW, Hermes SM, Chavkin CI, Drake CT, Morrison SF, Aicher SA. Kappa opioid receptor (KOR) and GAD67 immunoreactivity are found in OFF and NEUTRAL cells in the rostral ventromedial medulla. J Neurophysiol 2006; 96:3465-73. [PMID: 17005613 DOI: 10.1152/jn.00676.2006] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study combines functional and anatomical characterization of neurons in the rostral ventromedial medulla (RVM) to show distinct neurochemical phenotypes between functional classes of neurons. The RVM contains three functional classes of neurons: off cells show a pause in spontaneous activity prior to a nociceptive withdrawal reflex; on cell activity increases prior to a nociceptive reflex; and neutral cell activity does not change significantly during the nociceptive reflex. We determined if serotonin, glutamate decarboxylase (GAD67), or the kappa opioid receptor (KOR) were differentially located within these cell types as predicted by previous studies. In this study, RVM neurons were recorded extracellularly, functionally characterized, and juxtacellularly labeled with biotinamide. Fixed sections were processed for detection of biotinamide and immunfluorescence either for serotonin or for KOR and GAD67. In the first study, serotonin was found exclusively in a subset of neutral cells (33%). These data substantiate previous findings that serotonin is found in some neutral cells whose role in nociception remains unclear. In the second study, we found KOR immunoreactivity in most off (86%) and neutral (80%) cells but rarely in on (13%) cells. We also found GAD67 immunoreactivity in most off (93%) and neutral cells (80%) but less frequently in on cells (63%). Most KOR-immunoreactive cells (16 of 17) also contained GAD67 immunoreactivity regardless of cell classification. These findings support the hypothesis that KOR agonists directly inhibit off and neutral cell activity. The majority of the off and neutral cells are GABAergic, and some on cells are also GABAergic.
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Affiliation(s)
- Clayton W Winkler
- Neurological Sciences Institute, Oregon Health and Science University, 505 NW 185th Ave., Beaverton, OR 97006, USA
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21
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Ma J, Pan ZZ. Contribution of brainstem GABAA synaptic transmission to morphine analgesic tolerance. Pain 2006; 122:163-73. [PMID: 16527406 DOI: 10.1016/j.pain.2006.01.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2005] [Revised: 12/29/2005] [Accepted: 01/26/2006] [Indexed: 10/24/2022]
Abstract
Chronic opioid-induced analgesic tolerance remains a major obstacle to improving clinical management of moderate to severe chronic pain. Our understanding of the underlying mechanisms for opioid tolerance is only partially understood at present. In this study, we investigated the effects of chronic morphine on GABA(A) receptor-mediated synaptic transmission, a major opioid target for pain inhibition, and the behavioral role of GABA synaptic transmission in the development of morphine tolerance. In the nucleus raphe magnus (NRM), a critical brainstem site for opioid analgesia, the GABA(A) receptor-mediated inhibitory postsynaptic current (IPSC) was significantly increased in NRM neurons kept in a morphine-tolerant state from chronic morphine-treated rats. The potency of cAMP analogs for enhancing the GABA IPSC was also enhanced. The protein kinase A (PKA) inhibitor H89 reversed the chronic morphine-induced synaptic adaptation in GABA IPSCs. Behaviorally, a low dose of GABA(A) receptor antagonist bicuculline microinjected into the NRM, ineffective alone, blocked morphine antinociception in control rats, but failed to do so in morphine-tolerant rats. With chronic treatment through daily NRM microinjections, bicuculline augmented the development of morphine tolerance, whereas the GABA(A) receptor agonist muscimol or H89 significantly attenuated the development of morphine tolerance. These results suggest that chronic morphine increases GABA synaptic activity through upregulation of the AMP system in morphine-tolerant NRM neurons and that while chronic GABA(A) receptor antagonism in the NRM augments morphine tolerance, chronic activation of NRM GABA(A) receptors or PKA inhibition reduces morphine tolerance with increased analgesic efficacy of chronic morphine.
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Affiliation(s)
- Junyi Ma
- Department of Anesthesiology and Pain Medicine, The University of Texas-MD Anderson Cancer Center, Houston, TX, USA
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22
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Abstract
Opioids are frequently used for the treatment of moderate to severe acute and chronic pain. However, clinical evidence suggests that opioids can elicit increased sensitivity to noxious stimuli suggesting that administration of opioids can activate both, pain inhibitory and pain facilitatory systems. Acute receptor desensitization via uncoupling of the receptor from G proteins, upregulation of the cAMP pathway, activation of the N-methyl-D-aspartate (NMDA) receptor system and descending facilitation have been proposed as potential mechanisms underlying opioid-induced hyperalgesia. The tolerance results from a pain sensitization process more than from a decrease in the opioid effectiveness. Opioid-induced hyperalgesia and tolerance are observed both in animal and human experimental models. Brief exposures to mu-receptor agonists induce long-lasting hyperalgesic effects for days. Furthermore, the prolonged use of opioids in patients often requires increasing doses and may be accompanied by the development of abnormal pain. Successful strategies that may decrease or prevent opioid-induced hyperalgesia include the concomitant administration of drugs such as NMDA antagonists, alpha(2)-agonists, or nonsteroidal anti-inflammatory drugs (NSAID), opioid rotation, or combinations of opioids with different receptor selectivity.
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Affiliation(s)
- W Koppert
- Klinik für Anästhesiologie, Universitätsklinikum, Erlangen.
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23
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Zhu W, Pan ZZ. Mu-opioid-mediated inhibition of glutamate synaptic transmission in rat central amygdala neurons. Neuroscience 2005; 133:97-103. [PMID: 15893634 DOI: 10.1016/j.neuroscience.2005.02.004] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2005] [Revised: 02/04/2005] [Accepted: 02/07/2005] [Indexed: 12/15/2022]
Abstract
The central nucleus of the amygdala (CeA) plays an important role both in stimulus-reward learning for the reinforcing effects of drugs of abuse and in environmental condition-induced analgesia. Both of these two CeA functions involve the opioid system within the CeA. However, the pharmacological profiles of its opioid receptor system have not been fully studied and the synaptic actions of opioid receptors in the CeA are largely unknown. In this study with whole-cell voltage-clamp recordings in brain slices in vitro, we examined actions of opioid agonists on glutamate-mediated excitatory postsynaptic currents (EPSCs) in CeA neurons. Opioid peptide methionine-enkephalin (ME; 10 microM) produced a significant inhibition (38%) in the amplitude of evoked EPSCs, an action mimicked by the mu-opioid receptor agonist [D-Ala(2),N-MePhe(4),Gly-ol(5)]-enkephalin (DAMGO; 1 microM, 44%). Both effects of ME and DAMGO were abolished by the mu receptor antagonist CTAP (1 microM), suggesting a mu receptor-mediated effect. Neither delta-opioid receptor agonist [D-Pen(2),D-Pen(5)]-enkephalin (1 microM) nor kappa-opioid receptor agonist U69593 (300 nM) had any effect on the glutamate EPSC. ME significantly increased the paired-pulse ratio of the evoked EPSCs and decreased the frequency of miniature EPSCs without altering the amplitude of miniature EPSCs. Furthermore, the mu-opioid inhibition of the EPSC was blocked by 4-aminopyridine (4AP; 100 microM), a voltage-dependent potassium channel blocker, and by phospholipase A(2) inhibitors AACOCF(3) (10 microM) and quinacrine (10 microM). These results indicate that only the mu-opioid receptor is functionally present on presynaptic glutamatergic terminals in normal CeA neurons, and its activation reduces the probability of glutamate release through a signaling pathway involving phospholipase A(2) and the presynaptic, 4AP-sensitive potassium channel. This study provides evidence for the presynaptic regulation of glutamate synaptic transmission by mu-opioid receptors in CeA neurons.
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MESH Headings
- 4-Aminopyridine/pharmacology
- Amygdala/cytology
- Amygdala/drug effects
- Amygdala/physiology
- Analgesics, Opioid/pharmacology
- Animals
- Electrophysiology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Enkephalin, Methionine/pharmacology
- Enzyme Inhibitors/pharmacology
- Excitatory Postsynaptic Potentials/drug effects
- Glutamic Acid/physiology
- Male
- Neurons/physiology
- Patch-Clamp Techniques
- Peptide Fragments
- Peptides/pharmacology
- Phospholipases A/antagonists & inhibitors
- Phospholipases A/metabolism
- Potassium Channel Blockers/pharmacology
- Rats
- Rats, Wistar
- Receptors, Opioid, mu/agonists
- Receptors, Opioid, mu/antagonists & inhibitors
- Receptors, Opioid, mu/physiology
- Receptors, Presynaptic/drug effects
- Receptors, Presynaptic/metabolism
- Signal Transduction/physiology
- Somatostatin
- Synaptic Transmission/drug effects
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Affiliation(s)
- W Zhu
- Department of Anesthesiology, the University of Texas-MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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24
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Souter KJ, Davies JM, Loeser JD, Fitzgibbon DR. Continuous Intrathecal Meperidine for Severe Refractory Cancer Pain. Clin J Pain 2005; 21:193-6. [PMID: 15722815 DOI: 10.1097/00002508-200503000-00013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The control of severe cancer pain may be problematic despite advances in pain management. Patients with severe intractable pain and/or intractable side effects may require aggressive interventional pain management strategies including the administration of medications by the continuous intrathecal route and/or neurosurgical procedures. Various medications, including opioids, local anesthetics, and alpha-2 agonists may be used intrathecally for the control of cancer pain. Failure of the intrathecal route may require the additional use of neurosurgical procedures such as cordotomy for pain control. We describe a case of severe cancer pain refractory to conventional intrathecal medications and cordotomy that was successfully managed by the addition of meperidine to the intrathecal regimen.
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Affiliation(s)
- Karen J Souter
- Pain Service and Department of Anesthesiology, University of Washington School of Medicine, Seattle, WA 98195, USA.
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25
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Bie B, Pan ZZ. Increased glutamate synaptic transmission in the nucleus raphe magnus neurons from morphine-tolerant rats. Mol Pain 2005; 1:7. [PMID: 15813995 PMCID: PMC1074357 DOI: 10.1186/1744-8069-1-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Accepted: 02/09/2005] [Indexed: 05/02/2023] Open
Abstract
Currently, opioid-based drugs are the most effective pain relievers that are widely used in the treatment of pain. However, the analgesic efficacy of opioids is significantly limited by the development of tolerance after repeated opioid administration. Glutamate receptors have been reported to critically participate in the development and maintenance of opioid tolerance, but the underlying mechanisms remain unclear. Using whole-cell voltage-clamp recordings in brainstem slices, the present study investigated chronic morphine-induced adaptations in glutamatergic synaptic transmission in neurons of the nucleus raphe magnus (NRM), a key supraspinal relay for pain modulation and opioid analgesia. Chronic morphine significantly increased glutamate synaptic transmission exclusively in one class of NRM cells that contains μ-opioid receptors in a morphine-tolerant state. The adenylyl cyclase activator forskolin and the cAMP analog 8-bromo-cAMP mimicked the chronic morphine effect in control neurons and their potency in enhancing the glutamate synaptic current was significantly increased in neurons from morphine-tolerant rats. MDL12330a, an adenylyl cyclase inhibitor, and H89, a protein kinase A (PKA) inhibitor, reversed the increase in glutamate synaptic transmission induced by chronic morphine. In addition, PMA, a phorbol ester activator of protein kinase C (PKC), also showed an increased potency in enhancing the glutamate synaptic current in these morphine-tolerant cells. The PKC inhibitor GF109203X attenuated the chronic morphine effect. Taken together, these results suggest that chronic morphine increases presynaptic glutamate release in μ receptor-containing NRM neurons in a morphine-tolerant state, and that the increased glutamate synaptic transmission appears to involve an upregulation of both the cAMP/PKA pathway and the PKC pathway. This glutamate-mediated activation of these NRM neurons that are thought to facilitate spinal pain transmission may contribute to the reduced opioid analgesia during opioid tolerance.
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Affiliation(s)
- Bihua Bie
- Department of Anesthesiology, Unit 110, The University of Texas-MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas, 77030, USA
| | - Zhizhong Z Pan
- Department of Anesthesiology, Unit 110, The University of Texas-MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas, 77030, USA
- Department of Biochemistry & Molecular Biology, The University of Texas-MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, Texas, 77030, USA
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26
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Margolis EB, Hjelmstad GO, Bonci A, Fields HL. Both kappa and mu opioid agonists inhibit glutamatergic input to ventral tegmental area neurons. J Neurophysiol 2004; 93:3086-93. [PMID: 15615834 DOI: 10.1152/jn.00855.2004] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ventral tegmental area (VTA) plays a critical role in motivation and reinforcement. Kappa and mu opioid receptor (KOP-R and MOP-R) agonists microinjected into the VTA produce powerful and largely opposing motivational actions. Glutamate transmission within the VTA contributes to these motivational effects. Therefore information about opioid control of glutamate release onto VTA neurons is important. To address this issue, we performed whole cell patch-clamp recordings in VTA slices and measured excitatory postsynaptic currents (EPSCs). There are several classes of neuron in the VTA: principal, secondary, and tertiary. The KOP-R agonist (trans)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl] benzeneacetamide methane-sulfonate hydrate (U69593; 1 microM) produced a small reduction in EPSC amplitude in principal neurons (14%) and a significantly larger inhibition in secondary (47%) and tertiary (33%) neurons. The MOP-R agonist [D-Ala2, N-Me-Phe4, Gly-ol5]-enkephalin (DAMGO; 3 microM) inhibited glutamate release in principal (42%), secondary (45%), and tertiary neurons (35%). Unlike principal and tertiary neurons, in secondary neurons, the magnitude of the U69593 EPSC inhibition was positively correlated with that produced by DAMGO. Finally, DAMGO did not occlude the U69593 effect in principal neurons, suggesting that some glutamatergic terminals are independently controlled by KOP and MOP receptor activation. These findings show that MOP-R and KOP-R agonists regulate excitatory input onto each VTA cell type.
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Affiliation(s)
- Elyssa B Margolis
- Ernest Gallo Clinic and Research Center, 5858 Horton St., Suite 200, Emeryville, CA 94608, USA.
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27
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Abstract
This paper is the 26th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2003 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology, Doctoral Sub-Program, Queens College, City University of New York, 65-30 Kissena Blvd., Flushing, NY 11367, USA.
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28
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Zhu W, Pan ZZ. Synaptic properties and postsynaptic opioid effects in rat central amygdala neurons. Neuroscience 2004; 127:871-9. [PMID: 15312899 DOI: 10.1016/j.neuroscience.2004.05.043] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/28/2004] [Indexed: 12/15/2022]
Abstract
An important output of amygdaloid nuclei, the central nucleus of the amygdala (CeA) not only mediates negative emotional behaviors, but also participates in the stimulus-reward learning and expression of motivational aspects of many drugs of abuse, and links environmentally stressful conditions such as fear to endogenous pain-inhibiting mechanisms. The endogenous opioid system in the CeA is crucial for both reward behaviors and environmental stress-induced analgesia. In this study using whole-cell voltage-clamp recordings, we investigated synaptic inputs and the postsynaptic effects of opioid agonists in CeA neurons. We found that synaptic inputs evoked within the CeA were mediated by both glutamate and GABA, but those evoked from the basolateral amygdala were primarily glutamatergic. Based on membrane properties, three types of cells were characterized. Type A neurons had no spike accommodation while type B neurons displayed characteristic accommodating response. Type A neurons were further classified as either A1 or A2, based on differences in resting membrane potential and the amplitude of after-hyperpolarizing potential. micro-Opioid receptor agonists hyperpolarized a subpopulation of CeA neurons, of which the vast majority was type A1. This micro agonist-induced hyperpolarization was mediated by the opening of inwardly rectifying potassium channels. In contrast, the kappa-opioid receptor agonist hyperpolarized only type B neurons. These results illustrate three types of CeA neurons with distinctive membrane properties and differential responses to opioid agonists. They may represent functionally distinct CeA cell groups for the integration and execution of CeA outputs in the aforementioned CeA functions.
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Affiliation(s)
- W Zhu
- Department of Symptom Research, Unit 110, The University of Texas-MD Anderson Cancer Center, 1515 Holcombe Boulevard, Houston, TX 77030, USA
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29
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Meng ID, Johansen JP, Harasawa I, Fields HL. Kappa opioids inhibit physiologically identified medullary pain modulating neurons and reduce morphine antinociception. J Neurophysiol 2004; 93:1138-44. [PMID: 15456805 DOI: 10.1152/jn.00320.2004] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Microinjection of kappa opioid receptor (KOR) agonists into the rostral ventromedial medulla (RVM) attenuates mu-opioid receptor mediated antinociception and stress-induced analgesia, yet is also reported to have an analgesic effect. To determine how KOR agonists produce both antinociceptive and antianalgesic actions within the RVM, the KOR agonist U69593 was microinjected directly into the RVM while concurrently monitoring tail flick latencies and RVM neuronal activity. Among RVM neurons recorded in vivo, two types show robust changes in activity just prior to the nocifensive tail flick reflex: ON cells burst just prior to a tail flick and their activity is pronociceptive, whereas OFF cells pause just prior to the tail flick and their activity is antinociceptive. Although RVM microinjection of U69593 did not affect tail flick latencies on its own, it did attenuate the on cell burst, an effect blocked by co-injection of the KOR antagonist, nor-binaltorphimine (nor-BNI). Furthermore, U69593 inhibited ongoing activity in subsets of OFF cells (4/11) and NEUTRAL cells (3/9). Microinjection of U69593 into the RVM also attenuated morphine antinociception and suppressed the excitation of off cells. Together with previous in vivo and in vitro studies, these results are consistent with the idea that KOR agonists can be either pronociceptive through direct inhibition of OFF cells, or antianalgesic through both postsynaptic inhibition and presynaptic inhibition of glutamate inputs to RVM OFF cells.
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Affiliation(s)
- I D Meng
- Department of Neurology, University of California, San Francisco, California, USA.
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30
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de los Santos-Arteaga M, Sierra-Domínguez SA, Fontanella GH, Delgado-García JM, Carrión AM. Analgesia induced by dietary restriction is mediated by the kappa-opioid system. J Neurosci 2003; 23:11120-6. [PMID: 14657170 PMCID: PMC6741040] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/27/2023] Open
Abstract
Progress in the control and treatment of pain may be facilitated by a better understanding of mechanisms underlying nociceptive processing. Here we show that mice subjected to an intermittent fasting diet (IFD) display markedly reduced responses in models of thermal and visceral pain compared with mice fed ad libitum (AL). Pharmacological analyses suggest that a change in the endogenous kappa-opioid system underlies IFD-induced analgesia. The levels of prodynorphin mRNA and kappa-opioid receptors in the spinal cord are higher in IFD than in AL mice. Furthermore, in spinal cord nuclear protein extracts, the activity of the transcriptional repressor DREAM (downstream regulatory element antagonist modulator), the main regulator of prodynorphin expression, is lower in IFD than in AL mice. Finally, c-Fos expression in dorsal spinal cord after noxious stimulation is significantly lower in IFD than in AL animals, indicating that dynorphin could block nociceptive information at the spinal cord. These results suggest that dietary restriction together with administration of kappa-opioid agonists could be useful as a new therapeutic approach for pain relief.
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