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Guerrero-Alba R, Valdez-Morales EE, Jiménez-Vargas NN, Bron R, Poole D, Reed D, Castro J, Campaniello M, Hughes PA, Brierley SM, Bunnett N, Lomax AE, Vanner S. Co-expression of μ and δ opioid receptors by mouse colonic nociceptors. Br J Pharmacol 2018; 175:2622-2634. [PMID: 29579315 DOI: 10.1111/bph.14222] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2017] [Revised: 02/27/2018] [Accepted: 03/01/2018] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND AND PURPOSE To better understand opioid signalling in visceral nociceptors, we examined the expression and selective activation of μ and δ opioid receptors by dorsal root ganglia (DRG) neurons innervating the mouse colon. EXPERIMENTAL APPROACH DRG neurons projecting to the colon were identified by retrograde tracing. δ receptor-GFP reporter mice, in situ hybridization, single-cell RT-PCR and μ receptor-specific antibodies were used to characterize expression of μ and δ receptors. Voltage-gated Ca2+ currents and neuronal excitability were recorded in small diameter nociceptive neurons (capacitance <30 pF) by patch clamp and ex vivo single-unit afferent recordings were obtained from the colon. KEY RESULTS In situ hybridization of oprm1 expression in Fast Blue-labelled DRG neurons was observed in 61% of neurons. μ and δ receptors were expressed by 36-46% of colon DRG neurons, and co-expressed by ~25% of neurons. μ and δ receptor agonists inhibited Ca2+ currents in DRG, effects blocked by opioid antagonists. One or both agonists inhibited action potential firing by colonic afferent endings. Incubation of neurons with supernatants from inflamed colon segments inhibited Ca2+ currents and neuronal excitability. Antagonists of μ, but not δ receptors, inhibited the effects of these supernatant on Ca2+ currents, whereas both antagonists inhibited their actions on neuronal excitability. CONCLUSIONS AND IMPLICATIONS A significant number of small diameter colonic nociceptors co-express μ and δ receptors and are inhibited by agonists and endogenous opioids in inflamed tissues. Thus, opioids that act at μ or δ receptors, or their heterodimers may be effective in treating visceral pain.
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Affiliation(s)
- Raquel Guerrero-Alba
- Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON, Canada
| | | | | | - Romke Bron
- Monash Institute of Pharmaceutical Sciences and Australian Research Council Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Parkville, VIC, Australia
| | - Daniel Poole
- Monash Institute of Pharmaceutical Sciences and Australian Research Council Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Parkville, VIC, Australia.,Department of Anatomy and Neuroscience, The University of Melbourne, Parkville, VIC, Australia
| | - David Reed
- Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON, Canada
| | - Joel Castro
- Visceral Pain Research Group, Human Physiology, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
| | - Melissa Campaniello
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
| | - Patrick A Hughes
- Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
| | - Stuart M Brierley
- Visceral Pain Research Group, Human Physiology, Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, SA, Australia.,Centre for Nutrition and Gastrointestinal Diseases, Discipline of Medicine, University of Adelaide, South Australian Health and Medical Research Institute (SAHMRI), Adelaide, SA, Australia
| | - Nigel Bunnett
- Monash Institute of Pharmaceutical Sciences and Australian Research Council Centre of Excellence in Convergent Bio-Nano Science and Technology, Monash University, Parkville, VIC, Australia.,Department of Pharmacology and Therapeutics, The University of Melbourne, Parkville, VIC, Australia.,Departments of Surgery and Pharmacology, Columbia University College of Physicians and Surgeons, New York, NY, USA
| | - Alan E Lomax
- Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON, Canada
| | - Stephen Vanner
- Gastrointestinal Diseases Research Unit, Queen's University, Kingston, ON, Canada
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Peppin JF, Raffa RB. Delta opioid agonists: a concise update on potential therapeutic applications. J Clin Pharm Ther 2015; 40:155-66. [PMID: 25726896 DOI: 10.1111/jcpt.12244] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2014] [Accepted: 12/24/2014] [Indexed: 01/23/2023]
Abstract
WHAT IS KNOWN AND OBJECTIVE The endogenous opioid system co-evolved with chemical defences, or at times symbiotic relationships, between plants and other autotrophs and heterotrophic predators - thus, it is not surprising that endogenous opioid ligands and exogenous mimetic ligands produce diverse physiological effects. Among the endogenous opioid peptides (endomorphins, enkephalins, dynorphins and nociception/orphanin FQ) derived from the precursors encoded by four genes (PNOC, PENK, PDYN and POMC) are the pentapeptides Met-enkephalin (Tyr-Gly-Gly-Phe-Met) and Leu-enkephalin (Tyr-Gly-Gly-Phe-Leu). The physiological effects of the enkephalins are mediated via 7-transmembrane G protein-coupled receptors, including delta opioid receptor (DOR). We present a concise update on the status of progress and opportunities of this approach. METHODS A literature search of the PUBMED database and a combination of keywords including delta opioid receptor, analgesia, mood and individual compounds identified therein, from industry and other source, and from www.clinicaltrials.com. RESULTS AND DISCUSSION DOR agonist and antagonist ligands have been developed with ever increasing affinity and selectivity for DOR over other opioid receptor subtypes and studied for therapeutic utility, primarily for pain relief, but also for other clinical endpoints. WHAT IS NEW AND CONCLUSION Selective DOR agonists have been designed with a large increase in therapeutic window for a variety of potential CNS applications including pain, depression, and learning and memory among others.
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Affiliation(s)
- J F Peppin
- Center for Bioethics, Pain Management and Medicine, University City, MO, USA; Mallinckrodt Pharmaceuticals, Hazelwood, MO, USA
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Nieto CT, Gonzalez-Nunez V, Rodríguez RE, Diez D, Garrido NM. Design, synthesis, pharmacological evaluation and molecular dynamics of β-amino acids morphan-derivatives as novel ligands for opioid receptors. Eur J Med Chem 2015; 101:150-62. [PMID: 26134550 DOI: 10.1016/j.ejmech.2015.06.025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2014] [Revised: 06/06/2015] [Accepted: 06/09/2015] [Indexed: 10/23/2022]
Abstract
Structure-Activity Relationship (SAR) is a current approach in the design of new pharmacological agents. We previously reported the synthesis of a novel analogue of morphine, a 2-azabicyclo[3.3.1]nonane, which contains a β-amino acid. This bicyclic core exhibits two distinctive chemical handles for further elaboration, which allowed us to create a library of morphan-containing compounds by in silico molecular docking on the μ opioid receptor. Lead candidates were synthesized and biological tests were performed to evaluate their ability to bind to opioid receptors. The four top compounds, three phenyl esters and an N-phenylethyl morphan derivative, were selected for Molecular Dynamics simulations to get topological and thermodynamic information. Aromatic morphan derivatives displayed an interacting domain which fits into a hydrophobic cleft and the effect of the substituents in their affinity was explained by the differences in the calculated binding free energies. Our results indicate that the 3D arrangement of the aromatic ring in the morphine derivatives is not a key issue for a specific ligand - μ receptor interaction. Thus, these morphan derivatives represent a new class of opioid receptor ligands which may be of great use in the clinical practice.
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Affiliation(s)
- Carlos T Nieto
- Departamento de Química Orgánica, Faculty of Chemistry, Universidad de Salamanca, Spain
| | - Veronica Gonzalez-Nunez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Neuroscience Institute of Castilla y Leon (INCyL), University of Salamanca, Institute of Biomedical Research of Salamanca (IBSAL), Spain
| | - Raquel E Rodríguez
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, Neuroscience Institute of Castilla y Leon (INCyL), University of Salamanca, Institute of Biomedical Research of Salamanca (IBSAL), Spain
| | - David Diez
- Departamento de Química Orgánica, Faculty of Chemistry, Universidad de Salamanca, Spain
| | - Narciso M Garrido
- Departamento de Química Orgánica, Faculty of Chemistry, Universidad de Salamanca, Spain.
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Abstract
This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 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, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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