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Esch T, Winkler J, Auwärter V, Gnann H, Huber R, Schmidt S. Neurobiological Aspects of Mindfulness in Pain Autoregulation: Unexpected Results from a Randomized-Controlled Trial and Possible Implications for Meditation Research. Front Hum Neurosci 2017; 10:674. [PMID: 28184192 PMCID: PMC5266722 DOI: 10.3389/fnhum.2016.00674] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2016] [Accepted: 12/19/2016] [Indexed: 01/22/2023] Open
Abstract
Background: Research has demonstrated that short meditation training may yield higher pain tolerance in acute experimental pain. Our study aimed at examining underlying mechanisms of this alleged effect. In addition, placebo research has shown that higher pain tolerance is mediated via endogenous neuromodulators: experimental inhibition of opioid receptors by naloxone antagonized this effect. We performed a trial to discern possible placebo from meditation-specific effects on pain tolerance and attention. Objectives: It was proposed that (i) meditation training will increase pain tolerance; (ii) naloxone will inhibit this effect; (iii) increased pain tolerance will correlate with improved attention performance and mindfulness. Methods: Randomized-controlled, partly blinded trial with 31 healthy meditation-naïve adults. Pain tolerance was assessed by the tourniquet test, attention performance was measured by Attention Network Test (ANT), self-perceived mindfulness by Freiburg Mindfulness Inventory. 16 participants received a 5-day meditation training, focusing on body/breath awareness; the control group (N = 15) received no intervention. Measures were taken before the intervention and on 3 consecutive days after the training, with all participants receiving either no infusion, naloxone infusion, or saline infusion (blinded). Blood samples were taken in order to determine serum morphine and morphine glucuronide levels by applying liquid chromatography-tandem mass spectrometry analysis. Results: The meditation group produced fewer errors in ANT. Paradoxically, increases in pain tolerance occurred in both groups (accentuated in control), and correlated with reported mindfulness. Naloxone showed a trend to decrease pain tolerance in both groups. Plasma analyses revealed sporadic morphine and/or morphine metabolite findings with no discernable pattern. Discussion: Main objectives could not be verified. Since underlying study goals had not been made explicit to participants, on purpose (framing effects toward a hypothesized mindfulness-pain tolerance correlation were thus avoided, trainees had not been instructed how to 'use' mindfulness, regarding pain), the question remains open whether lack of meditation effects on pain tolerance was due to these intended 'non-placebo' conditions, cultural effects, or other confounders, or on an unsuitable paradigm. Conclusion: Higher pain tolerance through meditation could not be confirmed.
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Affiliation(s)
- Tobias Esch
- Division of Integrative Health Promotion, Coburg University of Applied SciencesCoburg, Germany; School of Medicine, Faculty of Health, Witten/Herdecke UniversityWitten, Germany; Institute for General Medicine, University Hospital Essen, University of Duisburg-EssenEssen, Germany
| | - Jeremy Winkler
- Department of Psychosomatic Medicine, Medical Center, Medical Faculty, University of Freiburg Freiburg, Germany
| | - Volker Auwärter
- Institute of Forensic Medicine, Forensic Toxicology, Medical Center, Medical Faculty, University of Freiburg Freiburg, Germany
| | - Heike Gnann
- Institute of Forensic Medicine, Forensic Toxicology, Medical Center, Medical Faculty, University of Freiburg Freiburg, Germany
| | - Roman Huber
- Center for Complementary Medicine, Medical Center, Medical Faculty, University of Freiburg Freiburg, Germany
| | - Stefan Schmidt
- Department of Psychosomatic Medicine, Medical Center, Medical Faculty, University of FreiburgFreiburg, Germany; Institute for Transcultural Health Studies, European University ViadrinaFrankfurt (Oder), Germany
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Stefano GB, Mantione KJ, Králíčková M, Ptacek R, Kuzelova H, Esch T, Kream RM. Parkinson's disease, L-DOPA, and endogenous morphine: a revisit. Med Sci Monit 2012; 18:RA133-137. [PMID: 22847214 PMCID: PMC3560700 DOI: 10.12659/msm.883259] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2012] [Accepted: 06/04/2012] [Indexed: 11/09/2022] Open
Abstract
Clinical observations stemming from widespread employment of restorative L-3,4-dihydroxyphenylalanine (L-DOPA) therapy for management of dyskinesia in Parkinson's Disease (PD) patients implicate a regulatory role for endogenous morphine in central nervous system dopamine neurotransmission. Reciprocally, it appears that restorative L-DOPA administration has provided us with a compelling in vivo pharmacological model for targeting peripheral sites involved in endogenous morphine expression in human subjects. The biological activities underlying endogenous morphine expression and its interaction with its major precursor dopamine strongly suggest that endogenous morphine systems are reciprocally dysregulated in PD. These critical issues are examined from historical and current perspectives within our short review.
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Affiliation(s)
- George B. Stefano
- Neuroscience Research Institute, State University of New York – College at Old Westbury, Old Westbury, NY, U.S.A
- Clinic of Psychiatry, 1 Faculty of Medicine, Charles University in Prague, Czech Republic
| | - Kirk J. Mantione
- Neuroscience Research Institute, State University of New York – College at Old Westbury, Old Westbury, NY, U.S.A
| | - Milena Králíčková
- Department of Histology and Embryology, Faculty of Medicine in Pilsen, Charles University in Prague, Czech Republic
| | - Radek Ptacek
- Neuroscience Research Institute, State University of New York – College at Old Westbury, Old Westbury, NY, U.S.A
- Clinic of Psychiatry, 1 Faculty of Medicine, Charles University in Prague, Czech Republic
| | - Hana Kuzelova
- Clinic of Psychiatry, 1 Faculty of Medicine, Charles University in Prague, Czech Republic
- Department of Biology and Medical Genetics, 2 Faculty of Medicine, Charles University in Prague, Czech Republic
| | - Tobias Esch
- Neuroscience Research Institute, State University of New York – College at Old Westbury, Old Westbury, NY, U.S.A
- Division of Integrative Health Promotion, Coburg University of Applied Sciences, Germany
| | - Richard M. Kream
- Neuroscience Research Institute, State University of New York – College at Old Westbury, Old Westbury, NY, U.S.A
- Clinic of Psychiatry, 1 Faculty of Medicine, Charles University in Prague, Czech Republic
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Walwyn W, John S, Maga M, Evans CJ, Hales TG. Delta receptors are required for full inhibitory coupling of mu-receptors to voltage-dependent Ca(2+) channels in dorsal root ganglion neurons. Mol Pharmacol 2009; 76:134-43. [PMID: 19357247 DOI: 10.1124/mol.109.055913] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Recombinant micro and delta opioid receptors expressed in cell lines can form heterodimers with distinctive properties and trafficking. However, a role for opioid receptor heterodimerization in neurons has yet to be identified. The inhibitory coupling of opioid receptors to voltage-dependent Ca(2+) channels (VDCCs) is a relatively inefficient process and therefore provides a sensitive assay of altered opioid receptor function and expression. We examined micro-receptor coupling to VDCCs in dorsal root ganglion neurons of delta(+/+), delta(+/-), and delta(-/-) mice. Neurons deficient in delta receptors exhibited reduced inhibition of VDCCs by morphine and [D-Ala(2),Phe(4),Gly(5)-ol]-enkephalin (DAMGO). An absence of delta receptors caused reduced efficacy of DAMGO without affecting potency. An absence of delta receptors reduced neither the density of VDCCs nor their inhibition by either the GABA(B) receptor agonist baclofen or intracellular guanosine 5'-O-(3-thio)triphosphate. Flow cytometry revealed a reduction in micro-receptor surface expression in delta(-/-) neurons without altered DAMGO-induced internalization. There was no change in micro-receptor mRNA levels. D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2)-sensitive mu-receptor-coupling efficacy was fully restored to delta(+/+) levels in delta(-/-) neurons by expression of recombinant delta receptors. However, the dimerization-deficient delta-15 construct expressed in delta(-/-) neurons failed to fully restore the inhibitory coupling of micro-receptors compared with that seen in delta(+/+) neurons, suggesting that, although not essential for micro-receptor function, micro-delta receptor dimerization contributes to full micro-agonist efficacy. Because DAMGO exhibited a similar potency in delta(+/+) and delta(-/-) neurons and caused similar levels of internalization, the role for heterodimerization is probably at the level of receptor biosynthesis.
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Affiliation(s)
- Wendy Walwyn
- Department of Psychiatry and Biobehavioral Sciences, Center for Health Sciences, University of California, Los Angeles, CA, USA
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Walwyn W, Evans CJ, Hales TG. Beta-arrestin2 and c-Src regulate the constitutive activity and recycling of mu opioid receptors in dorsal root ganglion neurons. J Neurosci 2007; 27:5092-104. [PMID: 17494695 PMCID: PMC6672367 DOI: 10.1523/jneurosci.1157-07.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2007] [Revised: 03/30/2007] [Accepted: 04/01/2007] [Indexed: 11/21/2022] Open
Abstract
Beta-arrestins bind to agonist-activated G-protein-coupled receptors regulating signaling events and initiating endocytosis. In beta-arrestin2-/- (beta arr2-/-) mice, a complex phenotype is observed that includes altered sensitivity to morphine. However, little is known of how beta-arrestin2 affects mu receptor signaling. We investigated the coupling of mu receptors to voltage-gated Ca2+ channels (VGCCs) in beta arr2+/+ and beta arr2-/- dorsal root ganglion neurons. A lack of beta-arrestin2 reduced the maximum inhibition of VGCCs by morphine and DAMGO (D-Ala2-N-Me-Phe4-glycol5-enkephalin) without affecting agonist potency, the onset of receptor desensitization, or the functional contribution of N-type VGCCs. The reduction in inhibition was accompanied by increased naltrexone-sensitive constitutive inhibitory coupling of mu receptors to VGCCs. Agonist-independent mu receptor inhibitory coupling was insensitive to CTAP (Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH2), a neutral antagonist that inhibited the inverse agonist action of naltrexone. These functional changes were accompanied by diminished constitutive recycling and increased cell-surface mu receptor expression in beta arr2-/- compared with beta arr2+/+ neurons. Such changes could not be explained by the classical role of beta-arrestins in agonist-induced endocytosis. The localization of the nonreceptor tyrosine kinase c-Src appeared disrupted in beta arr2-/- neurons, and there was reduced activation of c-Src by DAMGO. Using the Src inhibitor PP2 [4-amino-5-(4-chlorophenyl)-(t-butyl)pyrazolo[3,4-d]pyrimidine], we demonstrated that defective Src signaling mimics the beta arr2-/- cellular phenotype of reduced mu agonist efficacy, increased constitutive mu receptor activity, and reduced constitutive recycling. We propose that beta-arrestin2 is required to target c-Src to constitutively active mu receptors, resulting in their internalization, providing another dimension to the complex role of beta-arrestin2 and c-Src in G-protein-coupled receptor function.
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MESH Headings
- Analgesics, Opioid/pharmacology
- Animals
- Arrestins/genetics
- Arrestins/metabolism
- CSK Tyrosine-Protein Kinase
- Calcium Channels/drug effects
- Calcium Channels/metabolism
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Cells, Cultured
- Endocytosis/drug effects
- Endocytosis/physiology
- Female
- Ganglia, Spinal/metabolism
- Male
- Membrane Potentials/drug effects
- Membrane Potentials/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Neurons, Afferent/drug effects
- Neurons, Afferent/metabolism
- Nociceptors/drug effects
- Nociceptors/metabolism
- Pain/metabolism
- Pain/physiopathology
- Patch-Clamp Techniques
- Protein Transport/drug effects
- Protein Transport/physiology
- Protein-Tyrosine Kinases/metabolism
- Receptors, G-Protein-Coupled/drug effects
- Receptors, G-Protein-Coupled/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- Signal Transduction/drug effects
- Signal Transduction/physiology
- beta-Arrestin 2
- beta-Arrestins
- src-Family Kinases
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Affiliation(s)
- Wendy Walwyn
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Christopher J. Evans
- Department of Psychiatry and Biobehavioral Sciences, Hatos Center, University of California, Los Angeles, Los Angeles, California 90095, and
| | - Tim G. Hales
- Departments of Pharmacology and Physiology, and Anesthesiology and Critical Care Medicine, The George Washington University, Washington, DC 20037
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Sadée W, Wang D, Bilsky EJ. Basal opioid receptor activity, neutral antagonists, and therapeutic opportunities. Life Sci 2005; 76:1427-37. [PMID: 15680308 DOI: 10.1016/j.lfs.2004.10.024] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Accepted: 10/07/2004] [Indexed: 11/24/2022]
Abstract
The mu opioid receptor (MOR, OPRM)--the principal receptor involved in narcotic addiction--has been shown to display basal (spontaneous, constitutive) signaling activity. Interaction with other signaling proteins, such as calmodulin, regulates basal MOR activity. Providing a mechanism for long-lasting regulation, basal MOR activity potentially plays a key role in addiction, in combination with gene regulation and synaptic remodeling. Recent results support a link to physical dependence--one of the main manifestations of addiction to drugs of abuse. The prototypical opioid antagonists, naloxone and naltrexone, were shown to act as inverse agonists in the morphine-dependent state (i.e., they suppress basal MOR signaling) and thereby appear to elicit or contribute to precipitated withdrawal. This affords the opportunity to explore therapeutic applications for neutral antagonists (blocking agonists at MOR without affecting basal activity) with reduced adverse effects. Neutral antagonists are promising drug candidates in the treatment of addiction and overdose, and of peripheral adverse effects of narcotic analgesics.
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Affiliation(s)
- Wolfgang Sadée
- Department of Pharmacology, College of Medicine and Public Health, The Ohio State University, Columbus, OH 43210, USA.
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Abstract
Mutations in the mu-opioid receptor--the primary site of action of opioid analgesics--are candidates for the variability of clinical opioid effects. This has been substantiated by recent advances in genetic research. A common mu-opioid receptor polymorphism was associated with higher demands for alfentanil or morphine for pain relief. It also decreased the potency of morphine for pupil constriction and experimental analgesia, but its molecular mechanisms are unclear. Another opioid receptor mutation greatly impaired receptor signalling in vitro, but is very rare. The accumulated evidence provides a solid basis for continuing research that should address the underlying molecular mechanisms and the role and benefits of OPRM1 genotyping for clinical pain therapy.
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Affiliation(s)
- Jörn Lötsch
- pharmazentrum frankfurt/ZAFES, Institute of Clinical Pharmacology, Johann Wolfgang Goethe-University, Theodor Stern Kai 7, 60590 Frankfurt am Main, Germany.
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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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