1
|
Dean E, Dominique A, Palillero A, Tran A, Paradis N, Wu C. Probing the Activation Mechanisms of Agonist DPI-287 to Delta-Opioid Receptor and Novel Agonists Using Ensemble-Based Virtual Screening with Molecular Dynamics Simulations. ACS OMEGA 2023; 8:32404-32423. [PMID: 37720760 PMCID: PMC10500586 DOI: 10.1021/acsomega.3c01918] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 08/16/2023] [Indexed: 09/19/2023]
Abstract
Pain drugs targeting mu-opioid receptors face major addiction problems that have caused an epidemic. The delta-opioid receptor (DOR) has shown to not cause addictive effects when bound to an agonist. While the active conformation of the DOR in complex with agonist DPI-287 has been recently solved, there are still no FDA-approved agonists targeting it, providing the opportunity for structure-based virtual screening. In this study, the conformational plasticity of the DOR was probed using molecular dynamics (MD) simulations, identifying two representative conformations from clustering analysis. The two MD conformations as well as the crystal conformation of DOR were used to screen novel compounds from the ZINC database (17 million compounds), in which 69 drugs were picked as potential compounds based on their docking scores. Notably, 37 out of the 69 compounds were obtained from the simulated conformations. The binding stability of the 69 compounds was further investigated using MD simulations. Based on the MM-GBSA binding energy and the predicted drug properties, eight compounds were chosen as the most favorable, six of which were from the simulated conformations. Using a dynamic network model, the communication between the crystal agonist and the top eight molecules with the receptor was analyzed to confirm if these novel compounds share a similar activation mechanism to the crystal ligand. Encouragingly, docking of these eight compounds to the other two opioid receptors (kappa and mu) suggests their good selectivity toward DOR.
Collapse
Affiliation(s)
- Emily Dean
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| | - AnneMarie Dominique
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| | - Americus Palillero
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| | - Annie Tran
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| | - Nicholas Paradis
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| | - Chun Wu
- Department of Molecular &
Cellular Biosciences, College of Science and Mathematics, Rowan University, Glassboro, New Jersey 08028, United States
| |
Collapse
|
2
|
Blaine AT, van Rijn RM. Receptor expression and signaling properties in the brain, and structural ligand motifs that contribute to delta opioid receptor agonist-induced seizures. Neuropharmacology 2023; 232:109526. [PMID: 37004753 PMCID: PMC11078570 DOI: 10.1016/j.neuropharm.2023.109526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Revised: 03/10/2023] [Accepted: 03/28/2023] [Indexed: 04/03/2023]
Abstract
The δ opioid receptor (δOR) is a therapeutic target for the treatment of various neurological disorders, such as migraines, chronic pain, alcohol use, and mood disorders. Relative to μ opioid receptor agonists, δOR agonists show lower abuse liability and may be potentially safer analgesic alternatives. However, currently no δOR agonists are approved for clinical use. A small number of δOR agonists reached Phase II trials, but ultimately failed to progress due to lack of efficacy. One side effect of δOR agonism that remains poorly understood is the ability of δOR agonists to produce seizures. The lack of a clear mechanism of action is partly driven by the fact that δOR agonists range in their propensity to induce seizure behavior, with multiple δOR agonists reportedly not causing seizures. There is a significant gap in our current understanding of why certain δOR agonists are more likely to induce seizures, and what signal-transduction pathway and/or brain area is engaged to produce these seizures. In this review we provide a comprehensive overview of the current state of knowledge of δOR agonist-mediated seizures. The review was structured to highlight which agonists produce seizures, which brain regions have been implicated and which signaling mediators have been examined in this behavior. Our hope is that this review will spur future studies that are carefully designed and aimed to solve the question why certain δOR agonists are seizurogenic. Obtaining such insight may expedite the development of novel δOR clinical candidates without the risk of inducing seizures. This article is part of the Special Issue on "Opioid-induced changes in addiction and pain circuits".
Collapse
Affiliation(s)
- Arryn T Blaine
- Purdue University, Department of Medicinal Chemistry and Molecular Pharmacology, West Lafayette, IN, 47907, USA; Purdue University Interdisciplinary Life Science graduate program, West Lafayette, IN, 47907, USA
| | - Richard M van Rijn
- Purdue University, Department of Medicinal Chemistry and Molecular Pharmacology, West Lafayette, IN, 47907, USA; Purdue Institute for Integrative Neuroscience, West Lafayette, IN, 47907, USA; Purdue Institute for Drug Discovery, West Lafayette, IN, 47907, USA; Septerna Inc., South San Francisco, CA, 94080, USA.
| |
Collapse
|
3
|
Dremencov E, Grinchii D, Romanova Z, Chomanic P, Lacinova L, Jezova D. Effects of chronic delta-opioid receptor agonist on the excitability of hippocampal glutamate and brainstem monoamine neurons, anxiety, locomotion, and habituation in rats. Pharmacol Rep 2023; 75:585-595. [PMID: 37060527 DOI: 10.1007/s43440-023-00485-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2023] [Revised: 04/03/2023] [Accepted: 04/06/2023] [Indexed: 04/16/2023]
Abstract
BACKGROUND Short-term treatment with non-peptide agonists of delta-opioid receptors, such as agonist SNC80, induced behavioral effects in rodents, which could be modulated via changes in central neurotransmission. The present experiments aimed at testing the hypothesis that chronic treatment with SNC80 induces anxiolytic effects associated with changes in hippocampal glutamate and brainstem monoamine pathways. METHODS Adult male Wistar rats were used in experiments. Rats were treated with SNC80 (3 mg/kg/day) for fourteen days. Neuronal excitability was assessed using extracellular in vivo single-unit electrophysiology. The behavioral parameters were examined using the elevated plus maze and open field tests. RESULTS Chronic SNC80 treatment increased the excitability of hippocampal glutamate and ventral tegmental area dopamine neurons and had no effect on the firing activity of dorsal raphe nucleus serotonin cells. Chronic SNC80 treatment induced anxiolytic effects, which were, however, confounded by increased locomotor activity clearly confirmed in an open field test. The ability to cope with stressful situations and habituation processes in a novel environment was not influenced by chronic treatment with SNC80. CONCLUSION Our study suggests that the psychoactive effects of SNC80 might be explained by its ability to stimulate hippocampal glutamate and mesolimbic dopamine transmission.
Collapse
Affiliation(s)
- Eliyahu Dremencov
- Institute of Molecular Physiology and Genetics, Center of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, Slovakia.
- Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia.
| | - Daniil Grinchii
- Institute of Molecular Physiology and Genetics, Center of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, Slovakia
| | - Zuzana Romanova
- Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University Bratislava, Bratislava, Slovakia
| | - Pavol Chomanic
- Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Comenius University Bratislava, Bratislava, Slovakia
| | - Lubica Lacinova
- Institute of Molecular Physiology and Genetics, Center of Biosciences, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava, Slovakia
| | - Daniela Jezova
- Institute of Experimental Endocrinology, Biomedical Research Center, Slovak Academy of Sciences, Bratislava, Slovakia
| |
Collapse
|
4
|
Blaine AT, Miao Y, Yuan J, Palant S, Liu RJ, Zhang ZY, van Rijn RM. Exploration of beta-arrestin isoform signaling pathways in delta opioid receptor agonist-induced convulsions. Front Pharmacol 2022; 13:914651. [PMID: 36059958 PMCID: PMC9428791 DOI: 10.3389/fphar.2022.914651] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2022] [Accepted: 07/13/2022] [Indexed: 11/17/2022] Open
Abstract
The δ-opioid receptor (δOR) has been considered as a therapeutic target in multiple neurological and neuropsychiatric disorders particularly as δOR agonists are deemed safer alternatives relative to the more abuse-liable µ-opioid receptor drugs. Clinical development of δOR agonists, however, has been challenging in part due to the seizure-inducing effects of certain δOR agonists. Especially agonists that resemble the δOR-selective agonist SNC80 have well-established convulsive activity. Close inspection suggests that many of those seizurogenic δOR agonists efficaciously recruit β-arrestin, yet surprisingly, SNC80 displays enhanced seizure activity in β-arrestin 1 knockout mice. This finding led us to hypothesize that perhaps β-arrestin 1 is protective against, whereas β-arrestin 2 is detrimental for δOR-agonist-induced seizures. To investigate our hypothesis, we characterized three different δOR agonists (SNC80, ADL5859, ARM390) in cellular assays and in vivo in wild-type and β-arrestin 1 and β-arrestin 2 knockout mice for seizure activity. We also investigated downstream kinases associated with β-arrestin-dependent signal transduction. We discovered that δOR agonist-induced seizure activity strongly and positively correlates with β-arrestin 2 efficacy for the agonist, but that indirect inhibition of ERK activation using the MEK inhibitor SL327 did not inhibit seizure potency and duration. Inhibition of the PI3K/AKT/mTOR signaling with honokiol but not PQR530, attenuated SNC80 seizure duration in β-arrestin 1 knockout, but honokiol did not reduce SNC80-induced seizures in wild-type mice. Ultimately, our results indicate that β-arrestin 2 is correlated with δOR agonist-induced seizure intensity, but that global β-arrestin 1 knockout mice are a poor model system to investigate their mechanism of action.
Collapse
Affiliation(s)
- Arryn T. Blaine
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
- Purdue Interdisciplinary Life Sciences Graduate Program, West Lafayette, IN, United States
| | - Yiming Miao
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
| | - Jinling Yuan
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
| | - Sophia Palant
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
| | - Rebecca J. Liu
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
| | - Zhong-Yin Zhang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
- Purdue Institute for Drug Discovery, West Lafayette, IN, United States
- Purdue University Cancer Center, West Lafayette, IN, United States
| | - Richard. M. van Rijn
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, United States
- Purdue Institute for Drug Discovery, West Lafayette, IN, United States
- Purdue University Cancer Center, West Lafayette, IN, United States
- Purdue Institute for Integrative Neuroscience, West Lafayette, IN, United States
- *Correspondence: Richard. M. van Rijn,
| |
Collapse
|
5
|
The Opioid System in Depression. Neurosci Biobehav Rev 2022; 140:104800. [PMID: 35914624 PMCID: PMC10166717 DOI: 10.1016/j.neubiorev.2022.104800] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2022] [Revised: 06/20/2022] [Accepted: 07/25/2022] [Indexed: 12/16/2022]
Abstract
Opioid receptors are widely distributed throughout the brain and play an essential role in modulating aspects of human mood, reward, and well-being. Accumulating evidence indicates the endogenous opioid system is dysregulated in depression and that pharmacological modulators of mu, delta, and kappa opioid receptors hold potential for the treatment of depression. Here we review animal and clinical data, highlighting evidence to support: dysregulation of the opioid system in depression, evidence for opioidergic modulation of behavioural processes and brain regions associated with depression, and evidence for opioidergic modulation in antidepressant responses. We evaluate clinical trials that have examined the safety and efficacy of opioidergic agents in depression and consider how the opioid system may be involved in the effects of other treatments, including ketamine, that are currently understood to exert antidepressant effects through non-opioidergic actions. Finally, we explore key neurochemical and molecular mechanisms underlying the potential therapeutic effects of opioid system engagement, that together provides a rationale for further investigation into this relevant target in the treatment of depression.
Collapse
|
6
|
Conibear AE, Asghar J, Hill R, Henderson G, Borbely E, Tekus V, Helyes Z, Palandri J, Bailey C, Starke I, von Mentzer B, Kendall D, Kelly E. A Novel G Protein-Biased Agonist at the δ Opioid Receptor with Analgesic Efficacy in Models of Chronic Pain. J Pharmacol Exp Ther 2019; 372:224-236. [PMID: 31594792 PMCID: PMC6978697 DOI: 10.1124/jpet.119.258640] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2019] [Accepted: 08/26/2019] [Indexed: 11/22/2022] Open
Abstract
Agonists at the δ opioid receptor are known to be potent antihyperalgesics in chronic pain models and effective in models of anxiety and depression. However, some δ opioid agonists have proconvulsant properties while tolerance to the therapeutic effects can develop. Previous evidence indicates that different agonists acting at the δ opioid receptor differentially engage signaling and regulatory pathways with significant effects on behavioral outcomes. As such, interest is now growing in the development of biased agonists as a potential means to target specific signaling pathways and potentially improve the therapeutic profile of δ opioid agonists. Here, we report on PN6047 (3-[[4-(dimethylcarbamoyl)phenyl]-[1-(thiazol-5-ylmethyl)-4-piperidylidene]methyl]benzamide), a novel G protein–biased and selective δ opioid agonist. In cell-based assays, PN6047 fully engages G protein signaling but is a partial agonist in both the arrestin recruitment and internalization assays. PN6047 is effective in rodent models of chronic pain but shows no detectable analgesic tolerance following prolonged treatment. In addition, PN6047 exhibited antidepressant-like activity in the forced swim test, and importantly, the drug had no effect on chemically induced seizures. PN6047 did not exhibit reward-like properties in the conditioned place preference test or induce respiratory depression. Thus, δ opioid ligands with limited arrestin signaling such as PN6047 may be therapeutically beneficial in the treatment of chronic pain states.
Collapse
Affiliation(s)
- Alexandra E Conibear
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Junaid Asghar
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Rob Hill
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Graeme Henderson
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Eva Borbely
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Valeria Tekus
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Zsuzsanna Helyes
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Josephine Palandri
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Chris Bailey
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Ingemar Starke
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Bengt von Mentzer
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - David Kendall
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| | - Eamonn Kelly
- School of Physiology, Pharmacology and Neuroscience, University of Bristol, Biomedical Sciences Building, University Walk, Bristol, United Kingdom (A.E.C., R.H., G.H., E.K.); Faculty of Pharmacy, Gomal University, Khyber Pakhtunkhwa, Pakistan (J.A.); PharmInVivo Ltd., Szentagothai Research Centre, Centre for Neuroscience and Department of Pharmacology and Pharmacotherapy, Medical School, University of Pécs, Pécs, Hungary (E.B., V.T., Z.H.); Department of Pharmacy and Pharmacology, University of Bath, Bath, United Kingdom (J.P., C.B.); and PharmNovo AB, Kungshamn, Sweden (I.S., B.v.M., D.K.)
| |
Collapse
|
7
|
Browne CA, Lucki I. Targeting opioid dysregulation in depression for the development of novel therapeutics. Pharmacol Ther 2019; 201:51-76. [PMID: 31051197 DOI: 10.1016/j.pharmthera.2019.04.009] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 04/23/2019] [Indexed: 02/07/2023]
Abstract
Since the serendipitous discovery of the first class of modern antidepressants in the 1950's, all pharmacotherapies approved by the Food and Drug Administration for major depressive disorder (MDD) have shared a common mechanism of action, increased monoaminergic neurotransmission. Despite the widespread availability of antidepressants, as many as 50% of depressed patients are resistant to these conventional therapies. The significant length of time required to produce meaningful symptom relief with these medications, 4-6 weeks, indicates that other mechanisms are likely involved in the pathophysiology of depression which may yield more viable targets for drug development. For decades, no viable candidate target with a different mechanism of action to that of conventional therapies proved successful in clinical studies. Now several exciting avenues for drug development are under intense investigation. One of these emerging targets is modulation of endogenous opioid tone. This review will evaluate preclinical and clinical evidence pertaining to opioid dysregulation in depression, focusing on the role of the endogenous ligands endorphin, enkephalin, dynorphin, and nociceptin/orphanin FQ (N/OFQ) and their respective receptors, mu (MOR), delta (DOR), kappa (KOR), and the N/OFQ receptor (NOP) in mediating behaviors relevant to depression and anxiety. Finally, putative opioid based antidepressants that are under investigation in clinical trials, ALKS5461, JNJ-67953964 (formerly LY2456302 and CERC-501) and BTRX-246040 (formerly LY-2940094) will be discussed. This review will illustrate the potential therapeutic value of targeting opioid dysregulation in developing novel therapies for MDD.
Collapse
Affiliation(s)
- Caroline A Browne
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, United States of America
| | - Irwin Lucki
- Department of Pharmacology and Molecular Therapeutics, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, United States of America.
| |
Collapse
|
8
|
Stanczyk MA, Livingston KE, Chang L, Weinberg ZY, Puthenveedu MA, Traynor JR. The δ-opioid receptor positive allosteric modulator BMS 986187 is a G-protein-biased allosteric agonist. Br J Pharmacol 2019; 176:1649-1663. [PMID: 30710458 DOI: 10.1111/bph.14602] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2018] [Revised: 12/18/2018] [Accepted: 01/07/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND AND PURPOSE The δ-opioid receptor is an emerging target for the management of chronic pain and depression. Biased signalling, the preferential activation of one signalling pathway over another downstream of δ-receptors, may generate better therapeutic profiles. BMS 986187 is a positive allosteric modulator of δ-receptors. Here, we ask if BMS 986187 can directly activate the receptor from an allosteric site, without an orthosteric ligand, and if a signalling bias is generated. EXPERIMENTAL APPROACH We used several clonal cell lines expressing δ-receptors, to assess effects of BMS 986187 on events downstream of δ-receptors by measuring G-protein activation, β-arrestin 2 recruitment, receptor phosphorylation, loss of surface receptor expression, ERK1/ERK2 phosphorylation, and receptor desensitization. KEY RESULTS BMS 986187 is a G protein biased allosteric agonist, relative to β-arrestin 2 recruitment. Despite showing direct and potent G protein activation, BMS 986187 has a low potency to recruit β-arrestin 2. This appears to reflect the inability of BMS 986187 to elicit any significant receptor phosphorylation, consistent with low receptor internalization and a slower onset of desensitization, compared with the full agonist SNC80. CONCLUSIONS AND IMPLICATIONS This is the first evidence of biased agonism mediated through direct binding to an allosteric site on an opioid receptor, without a ligand at the orthosteric site. Our data suggest that agonists targeting δ-receptors, or indeed any GPCR, through allosteric sites may be a novel way to promote signalling bias and thereby potentially produce a more specific pharmacology than can be observed by activation via the orthosteric site.
Collapse
Affiliation(s)
- M Alexander Stanczyk
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Kathryn E Livingston
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Louise Chang
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Zara Y Weinberg
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - Manojkumar A Puthenveedu
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| | - John R Traynor
- Department of Pharmacology and Edward F. Domino Research Center, University of Michigan Medical School, Ann Arbor, Michigan, USA
| |
Collapse
|
9
|
Vicente-Sanchez A, Dripps IJ, Tipton AF, Akbari H, Akbari A, Jutkiewicz EM, Pradhan AA. Tolerance to high-internalizing δ opioid receptor agonist is critically mediated by arrestin 2. Br J Pharmacol 2018; 175:3050-3059. [PMID: 29722902 DOI: 10.1111/bph.14353] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2017] [Revised: 04/16/2018] [Accepted: 04/20/2018] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND AND PURPOSE Opioid δ receptor agonists are potent antihyperalgesics in chronic pain models, but tolerance develops after prolonged use. Previous evidence indicates that distinct forms of tolerance occur depending on the internalization properties of δ receptor agonists. As arrestins are important in receptor internalization, we investigated the role of arrestin 2 (β-arrestin 1) in mediating the development of tolerance induced by high- and low-internalizing δ receptor agonists. EXPERIMENTAL APPROACH We evaluated the effect of two δ receptor agonists with similar analgesic potencies, but either high-(SNC80) or low-(ARM390) internalization properties in wild-type (WT) and arrestin 2 knockout (KO) mice. We compared tolerance to the antihyperalgesic effects of these compounds in a model of inflammatory pain. We also examined tolerance to the convulsant effect of SNC80. Furthermore, effect of chronic treatment with SNC80 on δ agonist-stimulated [35 S]-GTPγS binding was determined in WT and KO mice. KEY RESULTS Arrestin 2 KO resulted in increased drug potency, duration of action and decreased acute tolerance to the antihyperalgesic effects of SNC80. In contrast, ARM390 produced similar effects in both WT and KO animals. Following chronic treatment, we found a marked decrease in the extent of tolerance to SNC80-induced antihyperalgesia and convulsions in arrestin 2 KO mice. Accordingly, δ receptors remained functionally coupled to G proteins in arrestin 2 KO mice chronically treated with SNC80. CONCLUSIONS AND IMPLICATIONS Overall, these results suggest that δ receptor agonists interact with arrestins in a ligand-specific manner, and tolerance to high- but not low-internalizing agonists are preferentially regulated by arrestin 2.
Collapse
Affiliation(s)
- Ana Vicente-Sanchez
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA
| | - Isaac J Dripps
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA.,Department of Pharmacology, University of Michigan, Ann Arbor, MI, USA
| | - Alycia F Tipton
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA
| | - Heba Akbari
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA
| | - Areeb Akbari
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA
| | | | - Amynah A Pradhan
- Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA
| |
Collapse
|
10
|
Delta/mu opioid receptor interactions in operant conditioning assays of pain-depressed responding and drug-induced rate suppression: assessment of therapeutic index in male Sprague Dawley rats. Psychopharmacology (Berl) 2018; 235:1609-1618. [PMID: 29572653 PMCID: PMC5924452 DOI: 10.1007/s00213-018-4876-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 03/06/2018] [Indexed: 12/23/2022]
Abstract
RATIONALE AND OBJECTIVES Although delta/mu receptor interactions vary as a function of behavioral endpoint, there have been no assessments of these interactions using assays of pain-depressed responding. This is the first report of delta/mu interactions using an assay of pain-depressed behavior. METHODS A mult-cycle FR10 operant schedule was utilized in the presence of (nociception) and in the absence of (rate suppression) a lactic acid inflammatory pain-like manipulation. SNC80 and methadone were used as selective/high efficacy delta and mu agonists, respectively. Both SNC80 and methadone alone produced a dose-dependent restoration of pain-depressed responding and dose-dependent response rate suppression. Three fixed ratio mixtures, based on the relative potencies of the drugs in the nociception assay, also produced dose-dependent antinociception and sedation. Isobolographic analysis indicated that all three mixtures produced supra-additive antinociceptive effects and simply additive sedation effects. CONCLUSIONS The therapeutic index (TI) inversely varied as a function of amount of SNC80 in the mixture, such that lower amounts of SNC80 produced a higher TI, and larger amounts produced a lower TI. Compared to literature using standard pain-elicited assays, the orderly relationship between SNC80 and TI reported here may be a unique function of assessing pain-depressed behavior.
Collapse
|
11
|
Wang D, Tawfik VL, Corder G, Low SA, François A, Basbaum AI, Scherrer G. Functional Divergence of Delta and Mu Opioid Receptor Organization in CNS Pain Circuits. Neuron 2018; 98:90-108.e5. [PMID: 29576387 PMCID: PMC5896237 DOI: 10.1016/j.neuron.2018.03.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Revised: 01/19/2018] [Accepted: 03/02/2018] [Indexed: 12/21/2022]
Abstract
Cellular interactions between delta and mu opioid receptors (DORs and MORs), including heteromerization, are thought to regulate opioid analgesia. However, the identity of the nociceptive neurons in which such interactions could occur in vivo remains elusive. Here we show that DOR-MOR co-expression is limited to small populations of excitatory interneurons and projection neurons in the spinal cord dorsal horn and unexpectedly predominates in ventral horn motor circuits. Similarly, DOR-MOR co-expression is rare in parabrachial, amygdalar, and cortical brain regions processing nociceptive information. We further demonstrate that in the discrete DOR-MOR co-expressing nociceptive neurons, the two receptors internalize and function independently. Finally, conditional knockout experiments revealed that DORs selectively regulate mechanical pain by controlling the excitability of somatostatin-positive dorsal horn interneurons. Collectively, our results illuminate the functional organization of DORs and MORs in CNS pain circuits and reappraise the importance of DOR-MOR cellular interactions for developing novel opioid analgesics.
Collapse
MESH Headings
- Animals
- Anterior Horn Cells/chemistry
- Anterior Horn Cells/metabolism
- Anterior Horn Cells/pathology
- Central Nervous System/chemistry
- Central Nervous System/metabolism
- Central Nervous System/pathology
- Male
- Mice, Inbred C57BL
- Mice, Knockout
- Nerve Net/chemistry
- Nerve Net/metabolism
- Nerve Net/pathology
- Pain/metabolism
- Pain/pathology
- Pain Measurement/methods
- Posterior Horn Cells/chemistry
- Posterior Horn Cells/metabolism
- Posterior Horn Cells/pathology
- Receptors, Opioid, delta/biosynthesis
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, mu/biosynthesis
- Receptors, Opioid, mu/genetics
Collapse
Affiliation(s)
- Dong Wang
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Vivianne L Tawfik
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Gregory Corder
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Sarah A Low
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Amaury François
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA
| | - Allan I Basbaum
- Department of Anatomy, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Grégory Scherrer
- Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, CA 94304, USA; Department of Molecular and Cellular Physiology, Stanford University, Palo Alto, CA 94304, USA; Department of Neurosurgery, Stanford University, Palo Alto, CA 94304, USA; Stanford Neurosciences Institute, Stanford University, Palo Alto, CA 94304, USA; New York Stem Cell Foundation - Robertson Investigator, Stanford University, Palo Alto, CA 94304, USA.
| |
Collapse
|
12
|
Lynch JJ, Van Vleet TR, Mittelstadt SW, Blomme EAG. Potential functional and pathological side effects related to off-target pharmacological activity. J Pharmacol Toxicol Methods 2017; 87:108-126. [PMID: 28216264 DOI: 10.1016/j.vascn.2017.02.020] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 01/24/2017] [Accepted: 02/15/2017] [Indexed: 12/22/2022]
Abstract
Most pharmaceutical companies test their discovery-stage proprietary molecules in a battery of in vitro pharmacology assays to try to determine off-target interactions. During all phases of drug discovery and development, various questions arise regarding potential side effects associated with such off-target pharmacological activity. Here we present a scientific literature curation effort undertaken to determine and summarize the most likely functional and pathological outcomes associated with interactions at 70 receptors, enzymes, ion channels and transporters with established links to adverse effects. To that end, the scientific literature was reviewed using an on-line database, and the most commonly reported effects were summarized in tabular format. The resultant table should serve as a practical guide for research scientists and clinical investigators for the prediction and interpretation of adverse side effects associated with molecules interacting with components of this screening battery.
Collapse
Affiliation(s)
- James J Lynch
- AbbVie Inc., 1 North Waukegan Road, North Chicago, IL 60064, USA.
| | | | | | - Eric A G Blomme
- AbbVie Inc., 1 North Waukegan Road, North Chicago, IL 60064, USA
| |
Collapse
|
13
|
Abstract
Depression is a pervasive and debilitating mental disorder that is inadequately treated by current pharmacotherapies in a majority of patients. Although opioids have long been known to regulate mood states, the use of opioids to treat depression is rarely discussed. This chapter explores the preclinical and clinical evidence supporting the antidepressant-like effects of opioid ligands, and in particular, delta opioid receptor (DOR) agonists. DOR agonists have been shown to produce antidepressant-like effects in a number of animal models. Some DOR agonists also produce convulsions which has limited their clinical utility. However, DOR agonists that generate antidepressant-like effects without convulsions have recently been developed and these drugs are beginning to be evaluated in humans. Work investigating potential mechanisms of action for the antidepressant-like effects of DOR agonists is also explored. Understanding mechanisms that give rise to DOR-mediated behaviors is critical for the development of DOR drugs with improved safety and clinical utility, and future work should be devoted to elucidating these pathways.
Collapse
|
14
|
Chiang T, Sansuk K, van Rijn RM. β-Arrestin 2 dependence of δ opioid receptor agonists is correlated with alcohol intake. Br J Pharmacol 2016; 173:332-43. [PMID: 26507558 DOI: 10.1111/bph.13374] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/30/2015] [Accepted: 10/11/2015] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND AND PURPOSE δ Opioid receptor agonists are being developed as potential treatments for depression and alcohol use disorders. This is particularly interesting as depression is frequently co-morbid with alcohol use disorders. Yet we have previously shown that δ receptor agonists range widely in their ability to modulate alcohol intake; certain δ receptor agonists actually increase alcohol consumption in mice. We propose that variations in β-arrestin 2 recruitment contribute to the differential behavioural profile of δ receptor agonists. EXPERIMENTAL APPROACH We used three diarylmethylpiperazine-based non-peptidic δ receptor selective agonists (SNC80, SNC162 and ARM390) and three structurally diverse δ receptor agonists (TAN-67, KNT127 and NIH11082). We tested these agonists in cAMP and β-arrestin 2 recruitment assays and a behavioural assay of alcohol intake in male C57BL/6 mice. We used β-arrestin 2 knockout mice and a model of depression-like behaviour to further study the role of β-arrestin 2 in δ receptor pharmacology. KEY RESULTS All six tested δ receptor agonists were full agonists in the cAMP assay but displayed distinct β-arrestin 2 recruitment efficacy. The efficacy of δ receptor agonists to recruit β-arrestin 2 positively correlated with their ability to increase alcohol intake (P < 0.01). The effects of the very efficacious recruiter SNC80 on alcohol intake, alcohol place preference and depression-like behaviour were β-arrestin 2-dependent. CONCLUSIONS AND IMPLICATIONS Our finding that δ receptor agonists that strongly recruit β-arrestin 2 can increase alcohol intake carries important ramifications for drug development of δ receptor agonists for treatment of alcohol use disorders and depressive disorders.
Collapse
Affiliation(s)
- T Chiang
- Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA
| | | | | |
Collapse
|
15
|
Pellissier LP, Pujol CN, Becker JAJ, Le Merrer J. Delta Opioid Receptors: Learning and Motivation. Handb Exp Pharmacol 2016; 247:227-260. [PMID: 28035528 DOI: 10.1007/164_2016_89] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Delta opioid receptor (DOR) displays a unique, highly conserved, structure and an original pattern of distribution in the central nervous system, pointing to a distinct and specific functional role among opioid peptide receptors. Over the last 15 years, in vivo pharmacology and genetic models have allowed significant advances in the understanding of this role. In this review, we will focus on the involvement of DOR in modulating different types of hippocampal- and striatal-dependent learning processes as well as motor function, motivation, and reward. Remarkably, DOR seems to play a key role in balancing hippocampal and striatal functions, with major implications for the control of cognitive performance and motor function under healthy and pathological conditions.
Collapse
Affiliation(s)
- L P Pellissier
- Physiologie de la Reproduction et des Comportements, INRA UMR-0085, CNRS UMR-7247, INSERM, Université François Rabelais, IFCE, 37380, Nouzilly, France
| | - C N Pujol
- Département de Neurosciences, Institut de Génomique fonctionnelle, INSERM U-661, CNRS UMR-5203, 34094, Montpellier, France
| | - J A J Becker
- Physiologie de la Reproduction et des Comportements, INRA UMR-0085, CNRS UMR-7247, INSERM, Université François Rabelais, IFCE, 37380, Nouzilly, France
| | - J Le Merrer
- Physiologie de la Reproduction et des Comportements, INRA UMR-0085, CNRS UMR-7247, INSERM, Université François Rabelais, IFCE, 37380, Nouzilly, France.
| |
Collapse
|
16
|
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.
Collapse
Affiliation(s)
- J F Peppin
- Center for Bioethics, Pain Management and Medicine, University City, MO, USA; Mallinckrodt Pharmaceuticals, Hazelwood, MO, USA
| | | |
Collapse
|
17
|
Gibula-Bruzda E, Marszalek-Grabska M, Witkowska E, Izdebski J, Kotlinska JH. Enkephalin analog, cyclo[N(ε),N(β)-carbonyl-D-Lys(2),Dap(5)] enkephalinamide (cUENK6), inhibits the ethanol withdrawal-induced anxiety-like behavior in rats. Alcohol 2015; 49:229-36. [PMID: 25716198 DOI: 10.1016/j.alcohol.2015.01.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2014] [Revised: 01/20/2015] [Accepted: 01/22/2015] [Indexed: 01/08/2023]
Abstract
An analog of enkephalin, cyclo[N(ε),N(β)-carbonyl-D-Lys(2),Dap(5)] enkephalinamide (cUENK6), is predominantly a functional agonist of μ-opioid receptors (MOPr) and, to a lesser extent, of δ-opioid receptors (DOPr) in vitro. The aim of the present study was to determine whether cUENK6 could affect ethanol withdrawal-induced anxiety-like behavior in the elevated plus maze (EPM) test in rats. An anxiety-like effect of withdrawal was predicted to occur in the EPM test 24 h after the last ethanol administration (2 g/kg, intraperitoneally [i.p.]; 15% w/v once daily for 9 days). Ethanol withdrawal decreased the percent of time spent by rats in the open arms and the percent of open-arms entries. cUENK6 (0.25 nmol), given by intracerebroventricular (i.c.v.) injection, significantly reversed these anxiety-like effects of ethanol withdrawal and elevated the percent of time spent by rats in the open arms and the percent of open-arms entries. These effects of cUENK6 were significantly inhibited by the DOPr antagonist naltrindole (NTI) (5 nmol, i.c.v.), but not by the MOPr antagonist β-funaltrexamine (β-FNA) (5 nmol, i.c.v.). The preferential DOPr agonist [Leu(5)]-enkephalin (LeuEnk) (2.7 and 5.4 nmol, i.c.v.) and the MOPr agonist morphine (6.5 and 13 nmol, i.c.v.) reduced the anxiety-like effects of ethanol withdrawal. cUENK6 at the dose of 0.25 nmol did not disturb locomotor activity in the EPM, in contrast to cUENK6 at the dose of 0.5 nmol, and morphine at 6.5 and 13 nmol. However, similarly to LeuEnk, cUENK6 induced the anxiolytic-like effects in naïve rats. Thus, our study suggests that cUENK6 reduced ethanol withdrawal-induced anxiety-like behavior by activation of δ-opioid receptors rather than μ-opioid receptors.
Collapse
|
18
|
A novel anxiogenic role for the delta opioid receptor expressed in GABAergic forebrain neurons. Biol Psychiatry 2015; 77:404-15. [PMID: 25444168 PMCID: PMC4297504 DOI: 10.1016/j.biopsych.2014.07.033] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2014] [Revised: 07/15/2014] [Accepted: 07/24/2014] [Indexed: 01/10/2023]
Abstract
BACKGROUND The delta opioid receptor (DOR) is broadly expressed throughout the nervous system; it regulates chronic pain, emotional responses, motivation, and memory. Neural circuits underlying DOR activities have been poorly explored by genetic approaches. We used conditional mouse mutagenesis to elucidate receptor function in GABAergic neurons of the forebrain. METHODS We characterized DOR distribution in the brain of Dlx5/6-CreXOprd1(fl/fl) (Dlx-DOR) mice and tested main central DOR functions through behavioral testing. RESULTS The DOR proteins were strongly deleted in olfactory bulb and striatum and remained intact in cortex and basolateral amygdala. Olfactory perception, circadian activity, and despair-like behaviors were unchanged. In contrast, locomotor stimulant effects of SNC80 (DOR agonist) and SKF81297 (D1 agonist) were abolished and increased, respectively. The Dlx-DOR mice showed lower levels of anxiety in the elevated plus maze, opposing the known high anxiety in constitutive DOR knockout animals. Also, Dlx-DOR mice reached the food more rapidly in a novelty suppressed feeding task, despite their lower motivation for food reward observed in an operant paradigm. Finally, c-fos protein staining after novelty suppressed feeding was strongly reduced in amygdala, concordant with the low anxiety phenotype of Dlx-DOR mice. CONCLUSIONS We demonstrate that DORs expressed in the forebrain mediate the described locomotor effect of SNC80 and inhibit D1-stimulated hyperactivity. Our data also reveal an unanticipated anxiogenic role for this particular DOR subpopulation, with a potential novel adaptive role. In emotional responses, DORs exert dual anxiolytic and anxiogenic roles, both of which may have implications in the area of anxiety disorders.
Collapse
|
19
|
Mabrouk OS, Viaro R, Volta M, Ledonne A, Mercuri N, Morari M. Stimulation of δ opioid receptor and blockade of nociceptin/orphanin FQ receptor synergistically attenuate parkinsonism. J Neurosci 2014; 34:12953-62. [PMID: 25253844 PMCID: PMC6608339 DOI: 10.1523/jneurosci.4677-13.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2013] [Revised: 06/25/2014] [Accepted: 07/03/2014] [Indexed: 11/21/2022] Open
Abstract
δ opioid peptide (DOP) receptors are considered a therapeutic target in Parkinson's disease, although the use of DOP agonists may be limited by side effects, including convulsions. To circumvent this issue, we evaluated whether blockade of nociceptin/orphanin FQ (N/OFQ) tone potentiated the antiparkinsonian effects of DOP agonists, thus allowing for reduction of their dosage. Systemic administration of the N/OFQ receptor (NOP) antagonist J-113397 [(3R,4R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1,3-dihydro-2H benzimidazol-2-one] and the DOP receptor agonist SNC-80 [(+)-4-[(αR)-α-(2S,5R)-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxy-benzyl]-N-N-diethylbenzamide] revealed synergistic attenuation of motor deficits in 6-hydroxydopamine hemilesioned rats and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated mice. In this model, repeated administration of the combination produced reproducible antiparkinsonian effects and was not associated with rescued striatal dopamine terminals. Microdialysis studies revealed that either systemic administration or local intranigral perfusion of J-113397 and SNC-80 led to the enhancement of nigral GABA, reduction of nigral Glu, and reduction of thalamic GABA levels, consistent with the view that NOP receptor blockade and DOP receptor stimulation caused synergistic overinhibition of nigro-thalamic GABA neurons. Whole-cell recording of GABA neurons in nigral slices confirmed that NOP receptor blockade enhanced the DOP receptor-induced effect on IPSCs via presynaptic mechanisms. Finally, SNC-80 more potently stimulated stepping activity in mice lacking the NOP receptor than wild-type controls, confirming the in vivo occurrence of an NOP-DOP receptor interaction. We conclude that endogenous N/OFQ functionally opposes DOP transmission in substantia nigra reticulata and that NOP receptor antagonists might be used in combination with DOP receptor agonists to reduce their dosage while maintaining their full therapeutic efficacy.
Collapse
Affiliation(s)
- Omar S Mabrouk
- Department of Medical Sciences, Section of Pharmacology, and National Institute of Neuroscience and
| | - Riccardo Viaro
- Department of Biomedical and Specialty Surgical Sciences, Section of Human Physiology, University of Ferrara, 44121 Ferrara, Italy, Department of Robotics, Brain, and Cognitive Sciences, Italian Institute of Technology, 16163 Genoa, Italy
| | - Mattia Volta
- Department of Medical Sciences, Section of Pharmacology, and National Institute of Neuroscience and
| | - Ada Ledonne
- Department of System Medicine, Neurophysiopathology, University of Rome "Tor Vergata," 00133 Rome, Italy, and Foundation S. Lucia, Institute for Inpatient Treatment and Scientific Studies, Laboratory of Experimental Neurology, 00143 Rome Italy
| | - Nicola Mercuri
- Department of System Medicine, Neurophysiopathology, University of Rome "Tor Vergata," 00133 Rome, Italy, and Foundation S. Lucia, Institute for Inpatient Treatment and Scientific Studies, Laboratory of Experimental Neurology, 00143 Rome Italy
| | - Michele Morari
- Department of Medical Sciences, Section of Pharmacology, and National Institute of Neuroscience and
| |
Collapse
|
20
|
Charfi I, Audet N, Bagheri Tudashki H, Pineyro G. Identifying ligand-specific signalling within biased responses: focus on δ opioid receptor ligands. Br J Pharmacol 2014; 172:435-48. [PMID: 24665881 DOI: 10.1111/bph.12705] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 03/17/2014] [Accepted: 03/20/2014] [Indexed: 01/13/2023] Open
Abstract
UNLABELLED Opioids activate GPCRs to produce powerful analgesic actions but at the same time induce side effects and generate tolerance, which restrict their clinical use. Reducing this undesired response profile has remained a major goal of opioid research and the notion of 'biased agonism' is raising increasing interest as a means of separating therapeutic responses from unwanted side effects. However, to fully exploit this opportunity, it is necessary to confidently identify biased signals and evaluate which type of bias may support analgesia and which may lead to undesired effects. The development of new computational tools has made it possible to quantify ligand-dependent signalling and discriminate this component from confounders that may also yield biased responses. Here, we analyse different approaches to identify and quantify ligand-dependent bias and review different types of confounders. Focus is on δ opioid receptor ligands, which are currently viewed as promising agents for chronic pain management. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
Collapse
Affiliation(s)
- I Charfi
- Sainte-Justine Hospital Research Center, Montreal, QC, Canada; Department of Pharmacology, Faculty of Medicine, University of Montreal, Montreal, QC, Canada
| | | | | | | |
Collapse
|
21
|
Gendron L, Mittal N, Beaudry H, Walwyn W. Recent advances on the δ opioid receptor: from trafficking to function. Br J Pharmacol 2014; 172:403-19. [PMID: 24665909 DOI: 10.1111/bph.12706] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Revised: 03/17/2014] [Accepted: 03/18/2014] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED Within the opioid family of receptors, δ (DOPrs) and μ opioid receptors (MOPrs) are typical GPCRs that activate canonical second-messenger signalling cascades to influence diverse cellular functions in neuronal and non-neuronal cell types. These receptors activate well-known pathways to influence ion channel function and pathways such as the map kinase cascade, AC and PI3K. In addition new information regarding opioid receptor-interacting proteins, downstream signalling pathways and resultant functional effects has recently come to light. In this review, we will examine these novel findings focusing on the DOPr and, in doing so, will contrast and compare DOPrs with MOPrs in terms of differences and similarities in function, signalling pathways, distribution and interactions. We will also discuss and clarify issues that have recently surfaced regarding the expression and function of DOPrs in different cell types and analgesia. LINKED ARTICLES This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.
Collapse
Affiliation(s)
- Louis Gendron
- Département de physiologie et biophysique, Institut de pharmacologie de Sherbrooke, Faculté de médecine et des sciences de la santé, Université de Sherbrooke, Sherbrooke, QC, Canada
| | | | | | | |
Collapse
|
22
|
Chu Sin Chung P, Kieffer BL. Delta opioid receptors in brain function and diseases. Pharmacol Ther 2013; 140:112-20. [PMID: 23764370 DOI: 10.1016/j.pharmthera.2013.06.003] [Citation(s) in RCA: 107] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Accepted: 05/15/2013] [Indexed: 01/02/2023]
Abstract
Evidence that the delta opioid receptor (DOR) is an attractive target for the treatment of brain disorders has strengthened in recent years. This receptor is broadly expressed in the brain, binds endogenous opioid peptides, and shows as functional profile highly distinct from those of mu and kappa opioid receptors. Our knowledge of DOR function has enormously progressed from in vivo studies using pharmacological tools and genetic approaches. The important role of this receptor in reducing chronic pain has been extensively overviewed; therefore this review focuses on facets of delta receptor activity relevant to psychiatric and other neurological disorders. Beneficial effects of DOR agonists are now well established in the context of emotional responses and mood disorders. DOR activation also regulates drug reward, inhibitory controls and learning processes, but whether delta compounds may represent useful drugs in the treatment of drug abuse remains open. Epileptogenic and locomotor-stimulating effects of delta agonists appear drug-dependent, and the possibility of biased agonism at DOR for these effects is worthwhile further investigations to increase benefit/risk ratio of delta therapies. Neuroprotective effects of DOR activity represent a forthcoming research area. Future developments in DOR research will benefit from in-depth investigations of DOR function at cellular and circuit levels.
Collapse
Affiliation(s)
- Paul Chu Sin Chung
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, UMR7104 CNRS/Université de Strasbourg, U964 INSERM, Illkirch, France
| | | |
Collapse
|
23
|
Fujii H, Takahashi T, Nagase H. Non-peptidic δ opioid receptor agonists and antagonists (2000 – 2012). Expert Opin Ther Pat 2013; 23:1181-208. [DOI: 10.1517/13543776.2013.804066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
|
24
|
Pradhan AA, Smith ML, Kieffer BL, Evans CJ. Ligand-directed signalling within the opioid receptor family. Br J Pharmacol 2013; 167:960-9. [PMID: 22708627 DOI: 10.1111/j.1476-5381.2012.02075.x] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The classic model of GPCR activation proposed that all agonists induce the same active receptor conformation. However, research over the last decade has shown that GPCRs exist in multiple conformations, and that agonists can stabilize different active states. The distinct receptor conformations induced by ligands result in distinct receptor-effector complexes, which produce varying levels of activation or inhibition of subsequent signalling cascades. This concept, referred to as ligand-directed signalling or biased agonism has important biological and therapeutic implications. Opioid receptors are G(i/o) GPCRs and regulate a number of important physiological functions, including pain, reward, mood, stress, gastrointestinal transport and respiration. A number of in vitro studies have shown biased agonism at the three opioid receptors (µ, δ and κ); however, in vivo consequences of this phenomenon have only recently been demonstrated. For the µ and δ opioid receptors, the majority of reported ligand selective behavioural effects are observed as differential adaptations to repeated drug administration. In terms of the κ opioid receptor, clear links between ligand-selective signalling events and specific in vivo responses have been recently characterized. Drugs for all three receptors are either already used or are being developed for clinical applications. There is clearly a need to better characterize the specific events that occur following agonist stimulation and how these relate to in vivo responses. This understanding could eventually lead to the development of tailor-made pharmacotherapies where advantageous drug effects can be selectively targeted over adverse effects.
Collapse
Affiliation(s)
- Amynah A Pradhan
- Semel Institute for Neuropsychiatry & Human Behavior, University of California Los Angeles, Los Angeles, CA 90024-1759, USA.
| | | | | | | |
Collapse
|
25
|
Lutz PE, Kieffer BL. Opioid receptors: distinct roles in mood disorders. Trends Neurosci 2012; 36:195-206. [PMID: 23219016 DOI: 10.1016/j.tins.2012.11.002] [Citation(s) in RCA: 345] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2012] [Revised: 09/20/2012] [Accepted: 11/05/2012] [Indexed: 12/20/2022]
Abstract
The roles of opioid receptors in pain and addiction have been extensively studied, but their function in mood disorders has received less attention. Accumulating evidence from animal research reveals that mu, delta and kappa opioid receptors (MORs, DORs and KORs, respectively) exert highly distinct controls over mood-related processes. DOR agonists and KOR antagonists have promising antidepressant potential, whereas the risk-benefit ratio of currently available MOR agonists as antidepressants remains difficult to evaluate, in addition to their inherent abuse liability. To date, both human and animal studies have mainly examined MORs in the etiology of depressive disorders, and future studies will address DOR and KOR function in established and emerging neurobiological aspects of depression, including neurogenesis, neurodevelopment, and social behaviors.
Collapse
Affiliation(s)
- Pierre-Eric Lutz
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de Recherche Scientifique (CNRS), Strasbourg, France
| | | |
Collapse
|
26
|
Nozaki C, Le Bourdonnec B, Reiss D, Windh RT, Little PJ, Dolle RE, Kieffer BL, Gavériaux-Ruff C. δ-Opioid mechanisms for ADL5747 and ADL5859 effects in mice: analgesia, locomotion, and receptor internalization. J Pharmacol Exp Ther 2012; 342:799-807. [PMID: 22700431 DOI: 10.1124/jpet.111.188987] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
N,N-diethyl-4-(5-hydroxyspiro[chromene-2,4'-piperidine]-4-yl) benzamide (ADL5859) and N,N-diethyl-3-hydroxy-4-(spiro[chromene-2,4'-piperidine]-4-yl)benzamide (ADL5747) are novel δ-opioid agonists that show good oral bioavailability and analgesic and antidepressive effects in the rat and represent potential drugs for chronic pain treatment. Here, we used genetic approaches to investigate molecular mechanisms underlying their analgesic effects in the mouse. We tested analgesic effects of ADL5859 and ADL5747 in mice by using mechanical sensitivity measures in both complete Freund's adjuvant and sciatic nerve ligation pain models. We examined their analgesic effects in δ-opioid receptor constitutive knockout (KO) mice and mice with a conditional deletion of δ-receptor in peripheral voltage-gated sodium channel (Nav)1.8-expressing neurons (cKO mice). Both ADL5859 and ADL5747, and the prototypical δ agonist 4-[(R)-[(2S,5R)-4-allyl-2,5-dimethyl-piperazin-1-yl]-(3-methoxyphenyl)methyl]-N,N-diethyl-benzamide (SNC80) as a control, significantly reduced inflammatory and neuropathic pain. The antiallodynic effects of all three δ-opioid agonists were abolished in constitutive δ-receptor KO mice and strongly diminished in δ-receptor cKO mice. We also measured two other well described effects of δ agonists, increase in locomotor activity and agonist-induced receptor internalization by using knock-in mice expressing enhanced green fluorescence protein-tagged δ receptors. In contrast to SNC80, ADL5859 and ADL5747 did not induce either hyperlocomotion or receptor internalization in vivo. In conclusion, both ADL5859 and ADL5747 showed efficient pain-reducing properties in the two models of chronic pain. Their effects were mediated by δ-opioid receptors, with a main contribution of receptors expressed on peripheral Nav1.8-positive neurons. The lack of in vivo receptor internalization and locomotor activation, typically induced by SNC80, suggests agonist-biased activity at the receptor for the two drugs.
Collapse
Affiliation(s)
- Chihiro Nozaki
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France
| | | | | | | | | | | | | | | |
Collapse
|
27
|
Negus SS, Rosenberg MB, Altarifi AA, O'Connell RH, Folk JE, Rice KC. Effects of the δ opioid receptor agonist SNC80 on pain-related depression of intracranial self-stimulation (ICSS) in rats. THE JOURNAL OF PAIN 2012; 13:317-27. [PMID: 22424913 DOI: 10.1016/j.jpain.2011.12.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 08/29/2011] [Revised: 12/01/2011] [Accepted: 12/08/2011] [Indexed: 12/16/2022]
Abstract
UNLABELLED The delta opioid receptor agonist SNC80 produces both antinociceptive and antidepressant effects in rodents. This profile suggests that SNC80 may also reverse prodepressant effects of pain. Accordingly, this study compared SNC80 effects in complementary assays of pain-stimulated and pain-depressed behavior in rats. Intraperitoneal injection of dilute acid served as an acute noxious visceral stimulus in rats to stimulate abdominal stretching (a pain-stimulated behavior) or depress intracranial self-stimulation of the medial forebrain bundle (ICSS; a pain-depressed behavior). When administered once per week to minimize acute tolerance, SNC80 (1-10 mg/kg IP) decreased acid-stimulated stretching but had little effect on acid-induced depression of ICSS. More frequent SNC80 administration produced tolerance to SNC80 effects on acid-stimulated stretching, but unmasked antinociception in the assay of acid-depressed ICSS. SNC80 did not facilitate ICSS in the absence of pain, and effects of SNC80 were not duplicated by ARM390, a reputed delta agonist congener of SNC80 that does not internalize delta receptors. These findings support continued consideration of delta agonists as candidate analgesics to treat prodepressant effects of pain and illustrate the potential for diametrically opposite effects of drug treatments on preclinical measures of pain-stimulated and pain-depressed behavior. PERSPECTIVE The delta opioid agonist SNC80 blocked pain-related depression of intracranial self-stimulation in rats, suggesting that delta agonists may be useful to treat prodepressant effects of pain. Repeated SNC80 produced tolerance to SNC80 antinociception in a conventional assay of pain-stimulated behavior but unmasked SNC80 antinociception in an assay of pain-depressed behavior.
Collapse
Affiliation(s)
- S Stevens Negus
- Department of Pharmacology and Toxicology, Virginia Commonwealth University, Richmond, VA 23220, USA.
| | | | | | | | | | | |
Collapse
|
28
|
Pradhan AA, Befort K, Nozaki C, Gavériaux-Ruff C, Kieffer BL. The delta opioid receptor: an evolving target for the treatment of brain disorders. Trends Pharmacol Sci 2011; 32:581-90. [PMID: 21925742 DOI: 10.1016/j.tips.2011.06.008] [Citation(s) in RCA: 218] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2011] [Revised: 06/18/2011] [Accepted: 06/21/2011] [Indexed: 12/14/2022]
Abstract
Compared to the better-known mu opioid receptor, delta opioid receptors have been relatively understudied. However, the development of highly selective delta opioid agonists and the availability of genetic mouse models have extended our knowledge of delta opioid receptors in vivo. Here we review recent developments in the characterization of delta opioid receptor biology and aspects of delta opioid receptor function that have potential for therapeutic targeting. Preclinical data have confirmed that delta opioid receptor activation reduces persistent pain and improves negative emotional states; clinical trials have been initiated to assess the effectiveness of delta opioid agonists in chronic pain and depression. Furthermore, a possible role for these receptors in neuroprotection is being investigated. The usefulness of targeting delta opioid receptors in drug abuse remains open and a role for these receptors in impulse control disorders is emerging. Finally, the recent demonstration of biased agonism at the delta opioid receptor in vivo opens novel perspectives towards targeting specific therapeutic effects through drug design.
Collapse
Affiliation(s)
- Amynah A Pradhan
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université de Strasbourg, 1 Rue Laurent Fries, 67404 Illkirch, France
| | | | | | | | | |
Collapse
|
29
|
Nagi K, Piñeyro G. Regulation of opioid receptor signalling: implications for the development of analgesic tolerance. Mol Brain 2011; 4:25. [PMID: 21663702 PMCID: PMC3138391 DOI: 10.1186/1756-6606-4-25] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2011] [Accepted: 06/13/2011] [Indexed: 11/10/2022] Open
Abstract
Opiate drugs are the most effective analgesics available but their clinical use is restricted by severe side effects. Some of these undesired actions appear after repeated administration and are related to adaptive changes directed at counteracting the consequences of sustained opioid receptor activation. Here we will discuss adaptations that contribute to the development of tolerance. The focus of the first part of the review is set on molecular mechanisms involved in the regulation of opioid receptor signalling in heterologous expression systems and neurons. In the second part we assess how adaptations that take place in vivo may contribute to analgesic tolerance developed during repeated opioid administration.
Collapse
Affiliation(s)
- Karim Nagi
- Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Canada
| | | |
Collapse
|
30
|
Ligand-directed trafficking of the δ-opioid receptor in vivo: two paths toward analgesic tolerance. J Neurosci 2011; 30:16459-68. [PMID: 21147985 DOI: 10.1523/jneurosci.3748-10.2010] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
δ-Opioid receptors are G-protein-coupled receptors that regulate nociceptive and emotional responses. It has been well established that distinct agonists acting at the same G-protein-coupled receptor can engage different signaling or regulatory responses. This concept, known as biased agonism, has important biological and therapeutic implications. Ligand-biased responses are well described in cellular models, however, demonstrating the physiological relevance of biased agonism in vivo remains a major challenge. The aim of this study was to investigate the long-term consequences of ligand-biased trafficking of the δ-opioid receptor, at both the cellular and behavioral level. We used δ agonists with similar binding and analgesic properties, but high [SNC80 ((+)-4-[(αR)-α-((2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl)-3-methoxybenzyl]-N,N-diethylbenzamide)]- or low [ARM390 (N,N-diethyl-4-(phenyl-piperidin-4-ylidenemethyl)-benzamide)]-internalization potencies. As we found previously, a single SNC80-but not ARM390-administration triggered acute desensitization of the analgesic response in mice. However, daily injections of either compound over 5 d produced full analgesic tolerance. SNC80-tolerant animals showed widespread receptor downregulation, and tolerance to analgesic, locomotor and anxiolytic effects of the agonist. Hence, internalization-dependent tolerance developed, as a result of generalized receptor degradation. In contrast, ARM390-tolerant mice showed intact receptor expression, but δ-opioid receptor coupling to Ca²+ channels was abolished in dorsal root ganglia. Concomitantly, tolerance developed for agonist-induced analgesia, but not locomotor or anxiolytic responses. Therefore, internalization-independent tolerance was produced by anatomically restricted adaptations leading to pain-specific tolerance. Hence, ligand-directed receptor trafficking of the δ-opioid receptor engages distinct adaptive responses, and this study reveals a novel aspect of biased agonism in vivo.
Collapse
|
31
|
Pradhan AAA, Becker JAJ, Scherrer G, Tryoen-Toth P, Filliol D, Matifas A, Massotte D, Gavériaux-Ruff C, Kieffer BL. In vivo delta opioid receptor internalization controls behavioral effects of agonists. PLoS One 2009; 4:e5425. [PMID: 19412545 PMCID: PMC2672171 DOI: 10.1371/journal.pone.0005425] [Citation(s) in RCA: 151] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2009] [Accepted: 03/30/2009] [Indexed: 11/19/2022] Open
Abstract
Background GPCRs regulate a remarkable diversity of biological functions, and are thus often targeted for drug therapies. Stimulation of a GPCR by an extracellular ligand triggers receptor signaling via G proteins, and this process is highly regulated. Receptor activation is typically accompanied by desensitization of receptor signaling, a complex feedback regulatory process of which receptor internalization is postulated as a key event. The in vivo significance of GPCR internalization is poorly understood. In fact, the majority of studies have been performed in transfected cell systems, which do not adequately model physiological environments and the complexity of integrated responses observed in the whole animal. Methods and Findings In this study, we used knock-in mice expressing functional fluorescent delta opioid receptors (DOR-eGFP) in place of the native receptor to correlate receptor localization in neurons with behavioral responses. We analyzed the pain-relieving effects of two delta receptor agonists with similar signaling potencies and efficacies, but distinct internalizing properties. An initial treatment with the high (SNC80) or low (AR-M100390) internalizing agonist equally reduced CFA-induced inflammatory pain. However, subsequent drug treatment produced highly distinct responses. Animals initially treated with SNC80 showed no analgesic response to a second dose of either delta receptor agonist. Concomitant receptor internalization and G-protein uncoupling were observed throughout the nervous system. This loss of function was temporary, since full DOR-eGFP receptor responses were restored 24 hours after SNC80 administration. In contrast, treatment with AR-M100390 resulted in retained analgesic response to a subsequent agonist injection, and ex vivo analysis showed that DOR-eGFP receptor remained G protein-coupled on the cell surface. Finally SNC80 but not AR-M100390 produced DOR-eGFP phosphorylation, suggesting that the two agonists produce distinct active receptor conformations in vivo which likely lead to differential receptor trafficking. Conclusions Together our data show that delta agonists retain full analgesic efficacy when receptors remain on the cell surface. In contrast, delta agonist-induced analgesia is abolished following receptor internalization, and complete behavioral desensitization is observed. Overall these results establish that, in the context of pain control, receptor localization fully controls receptor function in vivo. This finding has both fundamental and therapeutic implications for slow-recycling GPCRs.
Collapse
MESH Headings
- Animals
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Benzamides/pharmacology
- Biological Transport, Active/drug effects
- Cell Membrane/metabolism
- Cells, Cultured
- Green Fluorescent Proteins/chemistry
- Green Fluorescent Proteins/genetics
- Green Fluorescent Proteins/metabolism
- In Vitro Techniques
- Ligands
- Mice
- Mice, Transgenic
- Neurons/drug effects
- Neurons/physiology
- Pain/drug therapy
- Pain/physiopathology
- Phosphorylation
- Piperazines/pharmacology
- Piperidines/pharmacology
- Protein Conformation
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, delta/chemistry
- Receptors, Opioid, delta/genetics
- Receptors, Opioid, delta/physiology
- Recombinant Fusion Proteins/chemistry
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
Collapse
Affiliation(s)
- Amynah A. A. Pradhan
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Jérôme A. J. Becker
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Grégory Scherrer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Petra Tryoen-Toth
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Dominique Filliol
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Audrey Matifas
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Dominique Massotte
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Claire Gavériaux-Ruff
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
| | - Brigitte L. Kieffer
- Institut de Génétique et de Biologie Moléculaire et Cellulaire, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur, Illkirch, France
- * E-mail:
| |
Collapse
|
32
|
Bradbury FA, Zelnik JC, Traynor JR. G protein independent phosphorylation and internalization of the delta-opioid receptor. J Neurochem 2009; 109:1526-35. [PMID: 19344370 DOI: 10.1111/j.1471-4159.2009.06082.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Agonist activation of the delta-opioid receptor leads to internalization via G betagamma recruitment of G protein coupled receptor kinase-2, which phosphorylates the receptor at several sites, including Ser363, allowing beta-arrestin binding and localization to clathrin coated pits. Using human embryonic kidney cells expressing a delta-opioid receptor we tested the hypothesis that prevention of receptor coupling to G protein by treatment with pertussis toxin (PTX) will block these processes. PTX treatment did not reduce phosphorylation of delta-opioid receptor Ser363 in response to the agonist [D-Pen2, D-Pen5]enkephalin, or recruitment of beta-arrestin 2-green fluorescent protein to the membrane and only slowed, but did not prevent, [D-Pen2, D-Pen5]enkephalin-induced internalization. Similarly, PTX treatment only partially prevented the ability of the delta-opioid peptide agonists deltorphin II and [Met5]enkephalin and the non-peptide agonist BW373U86 to induce receptor internalization. No internalization was seen with morphine, oxymorphindole or the putative delta(1)-opioid agonist TAN-67 in the presence or absence of PTX, even though TAN-67 showed a strong activation of G protein, as measured by guanosine-5'-O-(3-[(35)S]thio)triphosphate binding. The ability of an agonist to stimulate phosphorylation at Ser363 was predictive of its capacity to induce internalization. The results suggest a role for G protein in delta-opioid receptor internalization, but show that alternative G protein independent pathways exist.
Collapse
Affiliation(s)
- Faye A Bradbury
- Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-5632, USA
| | | | | |
Collapse
|
33
|
Beaudry H, Proteau-Gagné A, Li S, Dory Y, Chavkin C, Gendron L. Differential noxious and motor tolerance of chronic delta opioid receptor agonists in rodents. Neuroscience 2009; 161:381-91. [PMID: 19328839 DOI: 10.1016/j.neuroscience.2009.03.053] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2008] [Revised: 03/19/2009] [Accepted: 03/20/2009] [Indexed: 01/28/2023]
Abstract
In the present study, we asked whether multiple intrathecal injections of deltorphin II, a selective delta opioid receptor (DOPR) agonist, induced DOPR tolerance in three behavioral assays. Unilateral inflammation caused by complete Freund's adjuvant (CFA) injection into the rat or mouse hind paw (CFA model) induced thermal hyperalgesic response that was transiently and dose-dependently reduced by intrathecal administration of deltorphin II or morphine. In both rodent species, the effect of deltorphin II was not modified by a single prior administration of deltorphin II, suggesting an absence of acute tolerance in this paradigm. Repeated administration of intrathecal deltorphin II or s.c. SB-235863 (five consecutive injections over 60 h) also failed to impair the antihyperalgesic response to delta opioid receptor agonist, whereas repeated intrathecal or s.c. injections of morphine induced a significant decrease in the subsequent thermal antihyperalgesic response to morphine. In mice, deltorphin II also induced a rapid, transient motor incoordination/ataxia-like behavior as tested with the accelerating rotarod. In contrast to the antihyperalgesic responses, tolerance to the motoric effect of deltorphin II was evident in mice previously exposed to multiple intrathecal agonist injections, but not multiple saline administrations. Using the tail flick antinociceptive test, we found that DOPR-mediated analgesia was significantly reduced by repeated exposure to deltorphin II. Altogether, these observations suggest that repeated injections of DOPR agonists induce differential tolerance effects on antihyperalgesic, antinociceptive, and motor incoordination/ataxia-like behaviors related to DOPR activation by deltorphin II.
Collapse
Affiliation(s)
- H Beaudry
- Department of Physiology and Biophysics, Université de Sherbrooke, Faculty of Medicine, 3001, 12e Avenue Nord, Sherbrooke, QC, Canada
| | | | | | | | | | | |
Collapse
|
34
|
Saitoh A, Yamada M, Yamada M, Takahashi K, Yamaguchi K, Murasawa H, Nakatani A, Tatsumi Y, Hirose N, Kamei J. Antidepressant-like effects of the delta-opioid receptor agonist SNC80 ([(+)-4-[(alphaR)-alpha-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-methoxyphenyl)methyl]-N,N-diethylbenzamide) in an olfactory bulbectomized rat model. Brain Res 2008; 1208:160-9. [DOI: 10.1016/j.brainres.2007.07.095] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 07/04/2007] [Accepted: 07/05/2007] [Indexed: 10/22/2022]
|
35
|
Jutkiewicz EM, Baladi MG, Folk JE, Rice KC, Woods JH. The delta-opioid receptor agonist SNC80 [(+)-4-[alpha(R)-alpha-[(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl]-(3-methoxybenzyl)-N,N-diethylbenzamide] synergistically enhances the locomotor-activating effects of some psychomotor stimulants, but not direct dopamine agonists, in rats. J Pharmacol Exp Ther 2007; 324:714-24. [PMID: 17986650 DOI: 10.1124/jpet.107.123844] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The nonpeptidic delta-opioid agonist SNC80 [(+)-4-[alpha(R)-alpha-[(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl]-(3-methoxybenzyl)-N,N-diethylbenzamide] produces many stimulant-like behavioral effects in rodents and monkeys, such as locomotor stimulation, generalization to cocaine in discrimination procedures, and antiparkinsonian effects. Tolerance to the locomotor-stimulating effects of SNC80 develops after a single administration of SNC80 in rats; it is not known whether cross-tolerance develops to the effects of other stimulant compounds. In the initial studies to determine whether SNC80 produced cross-tolerance to other stimulant compounds, it was discovered that amphetamine-stimulated locomotor activity was greatly enhanced in SNC80-pretreated rats. This study evaluated acute cross-tolerance between delta-opioid agonists and other locomotor-stimulating drugs. Locomotor activity was measured in male Sprague-Dawley rats implanted with radiotransmitters, and activity levels were recorded in the home cage environment. Three-hour SNC80 pretreatment produced tolerance to further delta-opioid receptor stimulation but also augmented greatly amphetamine-stimulated locomotor activity in a dose-dependent manner. Pretreatments with other delta-opioid agonists, (+)BW373U86 [(+)-4-[alpha(R)-alpha-[(2S,5R)-4-allyl-2,5-dimethyl-1-piperazinyl]-3-hydroxybenzyl]-N,N-diethylbenzamide] and oxymorphindole (17-methyl-6,7-dehydro-4,5-epoxy-3,14-dihydroxy-6,7,2',3'-indolomorphinan), also modified amphetamine-induced activity levels. SNC80 pretreatment enhanced the stimulatory effects of the dopamine/norepinephrine transporter ligands cocaine and nomifensine (1,2,3,4-tetrahydro-2-methyl-4-phenyl-8-isoquinolinanmine maleate salt), but not the direct dopamine receptor agonists SKF81297 [R-(+)-6-chloro-7,8-dihydroxy-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide] and quinpirole [trans-(-)-(4alphaR)-4,4a, 5,6,7,8,8a,9-octahydro-5-propyl-1H-pyrazolo[3,4-g] quinoline monohydrochloride]. In conclusion, SNC80 enhanced the locomotor-stimulating effects of monoamine transporter ligands suggesting that delta-opioid receptor activation might alter the functional activity of monoamine transporters or presynaptic monoamine terminals.
Collapse
Affiliation(s)
- Emily M Jutkiewicz
- Department of Pharmacology, University of Michigan Medical School, 1301 Medical Science Research Building III, 1150 W. Medical Center Drive, Ann Arbor, MI 48109-0632, USA.
| | | | | | | | | |
Collapse
|
36
|
Yadav PN, Chaturvedi K, Howells RD. Inhibition of agonist-induced down-regulation of the delta-opioid receptor with a proteasome inhibitor attenuates opioid tolerance in human embryonic kidney 293 cells. J Pharmacol Exp Ther 2006; 320:1186-94. [PMID: 17159161 DOI: 10.1124/jpet.106.113621] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was designed to test the hypothesis that inhibition of agonist-induced delta-receptor down-regulation would block the development of opioid tolerance in a cell-based model. A human embryonic kidney 293 cell line was established that expressed an epitope-tagged delta-opioid receptor (DOR). Treatment of DOR cells with Tyr-d-Ala-Gly-Phe-d-Leu-enkephalin (DADL) resulted in a time-dependent decrease in the B(max) of delta-opioid receptor binding sites and immunoreactive receptor protein. When cells were coincubated with the proteasome inhibitor N-benzyloxycarbonyl-l-leucyl-l-leucyl-l-leucinal (ZLLL) and DADL, the magnitude of the agonist-induced decrease in B(max) and immunoreactive receptor protein was reduced compared with DADL treatment alone. Acute treatment of DOR cells with DADL caused a 3-fold increase in the level of phosphorylated mitogen-activated protein (MAP) kinase. Prior exposure of DOR cells to DADL completely abrogated the agonist-induced activation of MAP kinase. When DOR cells were coincubated with DADL and ZLLL, the proteasome inhibitor prevented the loss of agonist activation of MAP kinase. Acute treatment of DOR cell membranes with DADL stimulated [(35)S]guanosine 5'-3-O-(thio-)triphosphate (GTPgammaS) binding. When DOR cells were preincubated with DADL, the agonist-induced increase in [(35)S]GTPgammaS binding was attenuated. Coincubation of ZLLL and agonist partially prevented the decreased responsiveness to agonist stimulation. The results of this study demonstrated that inhibition of agonist-induced down regulation with a proteasome inhibitor attenuated opioid tolerance in a cellular model, and suggest that coadministration of a proteasome inhibitor with chronic opioid agonist treatment may be useful for limiting opioid tolerance in vivo.
Collapse
Affiliation(s)
- Prem N Yadav
- Department of Biochemistry and Molecular Biology, UMDNJ-New Jersey Medical School, 185 South Orange Ave., Newark, NJ 07103, USA
| | | | | |
Collapse
|
37
|
Abstract
This paper is the 28th 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 2005 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, neurophysiology and transmitter release (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); immunological responses (Section 17).
Collapse
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.
| | | |
Collapse
|
38
|
Jutkiewicz EM, Baladi MG, Folk JE, Rice KC, Woods JH. The convulsive and electroencephalographic changes produced by nonpeptidic delta-opioid agonists in rats: comparison with pentylenetetrazol. J Pharmacol Exp Ther 2006; 317:1337-48. [PMID: 16537798 DOI: 10.1124/jpet.105.095810] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
delta-Opioid agonists produce convulsions and antidepressant-like effects in rats. It has been suggested that the antidepressant-like effects are produced through a convulsant mechanism of action either through overt convulsions or nonconvulsive seizures. This study evaluated the convulsive and seizurogenic effects of nonpeptidic delta-opioid agonists at doses that previously were reported to produce antidepressant-like effects. In addition, delta-opioid agonist-induced electroencephalographic (EEG) and behavioral changes were compared with those produced by the chemical convulsant pentylenetetrazol (PTZ). For these studies, EEG changes were recorded using a telemetry system before and after injections of the delta-opioid agonists [(+)-4-[(alphaR)-alpha-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-methoxyphenyl)methyl]-N,N-diethylbenz (SNC80) and [(+)-4-[alpha(R)-alpha-[(2S,5R)-2,5-dimethyl-4-(2-propenyl)-1-piperazinyl]-(3-hydroxyphenyl)methyl]-N,N-diethylbenzamide [(+)-BW373U86]. Acute administration of nonpeptidic delta-opioid agonists produced bilateral ictal and paroxysmal spike and/or sharp wave discharges. delta-Opioid agonists produced brief changes in EEG recordings, and tolerance rapidly developed to these effects; however, PTZ produced longer-lasting EEG changes that were exacerbated after repeated administration. Studies with antiepileptic drugs demonstrated that compounds used to treat absence epilepsy blocked the convulsive effects of nonpeptidic delta-opioid agonists. Overall, these data suggest that delta-opioid agonist-induced EEG changes are not required for the antidepressant-like effects of these compounds and that neural circuitry involved in absence epilepsy may be related to delta-opioid agonist-induced convulsions. In terms of therapeutic development, these data suggest that it may be possible to develop delta-opioid agonists devoid of convulsive properties.
Collapse
Affiliation(s)
- Emily M Jutkiewicz
- Department of Pharmacology, 1301 Medical Science Research Bldg. III, University of Michigan Medical School, Ann Arbor, MI 48109-0632, USA.
| | | | | | | | | |
Collapse
|