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Gamble MC, Williams BR, Singh N, Posa L, Freyberg Z, Logan RW, Puig S. Mu-opioid receptor and receptor tyrosine kinase crosstalk: Implications in mechanisms of opioid tolerance, reduced analgesia to neuropathic pain, dependence, and reward. Front Syst Neurosci 2022; 16:1059089. [PMID: 36532632 PMCID: PMC9751598 DOI: 10.3389/fnsys.2022.1059089] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 10/31/2022] [Indexed: 07/30/2023] Open
Abstract
Despite the prevalence of opioid misuse, opioids remain the frontline treatment regimen for severe pain. However, opioid safety is hampered by side-effects such as analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, or reward. These side effects promote development of opioid use disorders and ultimately cause overdose deaths due to opioid-induced respiratory depression. The intertwined nature of signaling via μ-opioid receptors (MOR), the primary target of prescription opioids, with signaling pathways responsible for opioid side-effects presents important challenges. Therefore, a critical objective is to uncouple cellular and molecular mechanisms that selectively modulate analgesia from those that mediate side-effects. One such mechanism could be the transactivation of receptor tyrosine kinases (RTKs) via MOR. Notably, MOR-mediated side-effects can be uncoupled from analgesia signaling via targeting RTK family receptors, highlighting physiological relevance of MOR-RTKs crosstalk. This review focuses on the current state of knowledge surrounding the basic pharmacology of RTKs and bidirectional regulation of MOR signaling, as well as how MOR-RTK signaling may modulate undesirable effects of chronic opioid use, including opioid analgesic tolerance, reduced analgesia to neuropathic pain, physical dependence, and reward. Further research is needed to better understand RTK-MOR transactivation signaling pathways, and to determine if RTKs are a plausible therapeutic target for mitigating opioid side effects.
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Affiliation(s)
- Mackenzie C. Gamble
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
- Molecular and Translational Medicine, Department of Medicine, Boston University School of Medicine, Boston, MA, United States
| | - Benjamin R. Williams
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
| | - Navsharan Singh
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
| | - Luca Posa
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
| | - Zachary Freyberg
- Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, United States
| | - Ryan W. Logan
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
- Center for Systems Neuroscience, Boston University, Boston, MA, United States
| | - Stephanie Puig
- Department of Pharmacology and Experimental Therapeutics, Boston University School of Medicine, Boston, MA, United States
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2
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Kember RL, Vickers-Smith R, Xu H, Toikumo S, Niarchou M, Zhou H, Hartwell EE, Crist RC, Rentsch CT, Davis LK, Justice AC, Sanchez-Roige S, Kampman KM, Gelernter J, Kranzler HR. Cross-ancestry meta-analysis of opioid use disorder uncovers novel loci with predominant effects in brain regions associated with addiction. Nat Neurosci 2022; 25:1279-1287. [PMID: 36171425 PMCID: PMC9682545 DOI: 10.1038/s41593-022-01160-z] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 08/11/2022] [Indexed: 11/09/2022]
Abstract
Despite an estimated heritability of ~50%, genome-wide association studies of opioid use disorder (OUD) have revealed few genome-wide significant loci. We conducted a cross-ancestry meta-analysis of OUD in the Million Veteran Program (N = 425,944). In addition to known exonic variants in OPRM1 and FURIN, we identified intronic variants in RABEPK, FBXW4, NCAM1 and KCNN1. A meta-analysis including other datasets identified a locus in TSNARE1. In total, we identified 14 loci for OUD, 12 of which are novel. Significant genetic correlations were identified for 127 traits, including psychiatric disorders and other substance use-related traits. The only significantly enriched cell-type group was CNS, with gene expression enrichment in brain regions previously associated with substance use disorders. These findings increase our understanding of the biological basis of OUD and provide further evidence that it is a brain disease, which may help to reduce stigma and inform efforts to address the opioid epidemic.
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Affiliation(s)
- Rachel L Kember
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Rachel Vickers-Smith
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
- Department of Epidemiology, University of Kentucky College of Public Health, Lexington, KY, USA
- Center on Drug and Alcohol Research, Department of Behavioral Science, University of Kentucky College of Medicine, Lexington, KY, USA
| | - Heng Xu
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Sylvanus Toikumo
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Maria Niarchou
- Department of Medicine, Division of Genetic Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Hang Zhou
- Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Emily E Hartwell
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Richard C Crist
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Christopher T Rentsch
- Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
- Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London, UK
| | - Lea K Davis
- Department of Medicine, Division of Genetic Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Amy C Justice
- Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
- Department of Health Policy and Management, Yale School of Public Health, New Haven, CT, USA
| | - Sandra Sanchez-Roige
- Department of Medicine, Division of Genetic Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
- Department of Psychiatry, University of California, San Diego, San Diego, CA, USA
| | - Kyle M Kampman
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA
| | - Joel Gelernter
- Veterans Affairs Connecticut Healthcare System, West Haven, CT, USA
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
| | - Henry R Kranzler
- Mental Illness Research, Education and Clinical Center, Crescenz Veterans Affairs Medical Center, Philadelphia, PA, USA.
- Department of Psychiatry, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, USA.
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3
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Puig S, Barker KE, Szott SR, Kann PT, Morris JS, Gutstein HB. Spinal Opioid Tolerance Depends upon Platelet-Derived Growth Factor Receptor- β Signaling, Not μ-Opioid Receptor Internalization. Mol Pharmacol 2020; 98:487-496. [PMID: 32723769 DOI: 10.1124/mol.120.119552] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 07/22/2020] [Indexed: 12/22/2022] Open
Abstract
Opioids are some of the most potent analgesics available. However, their effectiveness is limited by the development of analgesic tolerance. Traditionally, tolerance was thought to occur by termination of μ-opioid receptor (MOR) signaling via desensitization and internalization. Contradictory findings led to a more recent proposal that sustained MOR signaling caused analgesic tolerance. However, this view has also been called into question. We recently discovered that the platelet-derived growth factor receptor(PDGFR)-β signaling system is both necessary and sufficient to cause opioid tolerance. We therefore propose a completely new hypothesis: that opioid tolerance is mediated by selective cellular signals and is independent of MOR internalization. To test this hypothesis, we developed an automated software-based method to perform unbiased analyses of opioid-induced MOR internalization in the rat substantia gelatinosa. We induced tolerance with either morphine, which did not cause MOR internalization, or fentanyl, which did. We also blocked tolerance by administering morphine or fentanyl with the PDGFR-β inhibitor imatinib. We found that imatinib blocked tolerance without altering receptor internalization induced by either morphine or fentanyl. We also showed that imatinib blocked tolerance to other clinically used opioids. Our findings indicate that opioid tolerance is not dependent upon MOR internalization and support the novel hypothesis that opioid tolerance is mediated by intracellular signaling that can be selectively targeted. This suggests the exciting possibility that undesirable opioid side effects can be selectively eliminated, dramatically improving the safety and efficacy of opioids. SIGNIFICANCE STATEMENT: Classically, it was thought that analgesic tolerance to opioids was caused by desensitization and internalization of μ-opioid receptors (MORs). More recently, it was proposed that sustained, rather than reduced, MOR signaling caused tolerance. Here, we present conclusive evidence that opioid tolerance occurs independently of MOR internalization and that it is selectively mediated by platelet-derived growth factor receptor signaling. This novel hypothesis suggests that dangerous opioid side effects can be selectively targeted and blocked, improving the safety and efficacy of opioids.
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Affiliation(s)
- S Puig
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
| | - K E Barker
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
| | - S R Szott
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
| | - P T Kann
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
| | - J S Morris
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
| | - H B Gutstein
- Anesthesiology Institute, Allegheny Health Network, Pittsburgh, Pennsylvania (H.B.G.); University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania (S.P., S.R.S., P.T.K.); MD Anderson Cancer Center, Houston, Texas (K.E.B.); and Biostatistics Division, Perelman School of Medicine, Philadelphia, Pennsylvania (J.S.M.)
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EGFR Signaling Causes Morphine Tolerance and Mechanical Sensitization in Rats. eNeuro 2020; 7:ENEURO.0460-18.2020. [PMID: 32111605 PMCID: PMC7218007 DOI: 10.1523/eneuro.0460-18.2020] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2018] [Revised: 12/29/2018] [Accepted: 02/17/2020] [Indexed: 01/18/2023] Open
Abstract
The safety and efficacy of opioids are compromised as analgesic tolerance develops. Opioids are also ineffective against neuropathic pain. Recent reports have suggested that inhibitors of the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase (RTK), may have analgesic effects in cancer patients suffering from neuropathic pain. It has been shown that the platelet-derived growth factor receptor-β (PDGFR-β), an RTK that has been shown to interact with the EGFR, mediates opioid tolerance but does not induce analgesia. Therefore, we sought to determine whether EGFR signaling was involved in opioid tolerance and whether EGFR and PDGFR signaling could induce pain in rats. We found that gefitinib, an EGFR antagonist, eliminated morphine tolerance. In addition, repeated EGF administration rendered animals unresponsive to subsequent analgesic doses of morphine, a phenomenon we call "pre-tolerance." Using a nerve injury model, we found that gefitinib alone was not analgesic. Rather, it reversed insensitivity to morphine analgesia (pre-tolerance) caused by the release of EGF by injured nerves. We also showed that repeated, but not acute EGF or PDGF-BB administration induced mechanical hypersensitivity in rats. EGFR and PDGFR-β signaling interacted to produce this sensitization. EGFR was widely expressed in primary sensory afferent cell bodies, demonstrating a neuroanatomical substrate for our findings. Taken together, our results suggest a direct mechanistic link between opioid tolerance and mechanical sensitization. EGFR antagonism could eventually play an important clinical role in the treatment of opioid tolerance and neuropathic pain that is refractory to opioid treatment.
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Genome-Wide Association Study of Opioid Cessation. J Clin Med 2020; 9:jcm9010180. [PMID: 31936517 PMCID: PMC7019731 DOI: 10.3390/jcm9010180] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 12/20/2019] [Accepted: 01/03/2020] [Indexed: 01/10/2023] Open
Abstract
The United States is experiencing an epidemic of opioid use disorder (OUD) and overdose-related deaths. However, the genetic basis for the ability to discontinue opioid use has not been investigated. We performed a genome-wide association study (GWAS) of opioid cessation (defined as abstinence from illicit opioids for >1 year or <6 months before the interview date) in 1130 African American (AA) and 2919 European ancestry (EA) participants recruited for genetic studies of substance use disorders and who met lifetime Diagnostic and Statistical Manual of Mental Disorders, 5th Edition (DSM-5) criteria for OUD. Association tests performed separately within each ethnic group were combined by meta-analysis with results obtained from the Comorbidity and Trauma Study. Although there were no genome-wide significant associations, we found suggestive associations with nine independent loci, including three which are biologically relevant: rs4740988 in PTPRD (pAA + EA = 2.24 × 10−6), rs36098404 in MYOM2 (pEA = 2.24 × 10−6), and rs592026 in SNAP25-AS1 (pEA = 6.53 × 10−6). Significant pathways identified in persons of European ancestry (EA) are related to vitamin D metabolism (p = 3.79 × 10−2) and fibroblast growth factor (FGF) signaling (p = 2.39 × 10−2). UK Biobank traits including smoking and drinking cessation and chronic back pain were significantly associated with opioid cessation using GWAS-derived polygenic risk scores. These results provide evidence for genetic influences on opioid cessation, suggest genetic overlap with other relevant traits, and may indicate potential novel therapeutic targets for OUD.
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Growth Factor Signaling Regulates Mechanical Nociception in Flies and Vertebrates. J Neurosci 2019; 39:6012-6030. [PMID: 31138657 DOI: 10.1523/jneurosci.2950-18.2019] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 05/15/2019] [Accepted: 05/21/2019] [Indexed: 02/06/2023] Open
Abstract
Mechanical sensitization is one of the most difficult clinical pain problems to treat. However, the molecular and genetic bases of mechanical nociception are unclear. Here we develop a Drosophila model of mechanical nociception to investigate the ion channels and signaling pathways that regulate mechanical nociception. We fabricated von Frey filaments that span the subthreshold to high noxious range for Drosophila larvae. Using these, we discovered that pressure (force/area), rather than force per se, is the main determinant of aversive rolling responses to noxious mechanical stimuli. We demonstrated that the RTK PDGF/VEGF receptor (Pvr) and its ligands (Pvfs 2 and 3) are required for mechanical nociception and normal dendritic branching. Pvr is expressed and functions in class IV sensory neurons, whereas Pvf2 and Pvf3 are produced by multiple tissues. Constitutive overexpression of Pvr and its ligands or inducible overexpression of Pvr led to mechanical hypersensitivity that could be partially separated from morphological effects. Genetic analyses revealed that the Piezo and Pain ion channels are required for mechanical hypersensitivity observed upon ectopic activation of Pvr signaling. PDGF, but not VEGF, peptides caused mechanical hypersensitivity in rats. Pharmacological inhibition of VEGF receptor Type 2 (VEGFR-2) signaling attenuated mechanical nociception in rats, suggesting a conserved role for PDGF and VEGFR-2 signaling in regulating mechanical nociception. VEGFR-2 inhibition also attenuated morphine analgesic tolerance in rats. Our results reveal that a conserved RTK signaling pathway regulates baseline mechanical nociception in flies and rats.SIGNIFICANCE STATEMENT Hypersensitivity to touch is poorly understood and extremely difficult to treat. Using a refined Drosophila model of mechanical nociception, we discovered a conserved VEGF-related receptor tyrosine kinase signaling pathway that regulates mechanical nociception in flies. Importantly, pharmacological inhibition of VEGF receptor Type 2 signaling in rats causes analgesia and blocks opioid tolerance. We have thus established a robust, genetically tractable system for the rapid identification and functional analysis of conserved genes underlying mechanical pain sensitivity.
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Tang MM, Lin WJ, Pan YQ, Li YC. Fibroblast Growth Factor 2 Modulates Hippocampal Microglia Activation in a Neuroinflammation Induced Model of Depression. Front Cell Neurosci 2018; 12:255. [PMID: 30135647 PMCID: PMC6092504 DOI: 10.3389/fncel.2018.00255] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Accepted: 07/24/2018] [Indexed: 01/08/2023] Open
Abstract
Recent studies indicate that disturbed structure and function of microglia can cause depression and associated neurogenesis impairments. Our previous work has demonstrated that exogenous fibroblast growth factor 2 (FGF2) reverses the depressive-like behaviors and the impaired hippocampal neurogenesis in a neuroinflammatory model of depression. However, whether and how the antidepressant effects of FGF2 involve the modulation of microglia activation has not been elucidated. In this study, to examine the effects of FGF2 on microglia activation, exogenous FGF2 was supplemented to the lateral ventricle of rats during the neuroinflammatory state induced by central lipopolysaccharides (LPS) administrations. It was found that FGF2 infusions reversed the LPS-induced depressive-like behaviors and inhibited the hippocampal microglia activation. In LPS-treated rats, FGF2 decreased the level of pro-inflammatory cytokines including interlukin-1β (IL-1β), IL-6 and tumor necrosis factor (TNF)-α, increased the level of IL-10, the anti-inflammatory cytokine and reversed the decreased expression of CX3CL1, a chemokine mainly expressed by neurons and keeping microglia in surveillance. Further, we examined the effects of inhibited FGF2 signaling by administration of SU5402, an FGFR inhibitor. It was found that SU5402 itself evoked depressive-like behaviors, induced microglia activation, increased production of pro-inflammatory cytokines including IL-1β, IL-6 and TNF-α, and decreased the expression of CX3CL1. Two lines of results that FGF2 signaling and FGFR inhibitor can effectively but oppositely modulate the regulation of microglia and the generation of depressive-like behavior, suggesting that microglia-regulated mechanisms may underlie the antidepressant role of FGF2. The present data provide novel insights into the understanding of mechanism of neuroinflammation-associated depression and may serve as a novel mechanism-based target for the treatment of inflammation-related depression.
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Affiliation(s)
- Ming-Ming Tang
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China.,Institute of Zoology, Chinese Academy of Sciences, Beijing, China
| | - Wen-Juan Lin
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Yu-Qin Pan
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China.,Department of Psychology, University of Chinese Academy of Sciences, Beijing, China
| | - Ying-Cong Li
- CAS Key Laboratory of Mental Health, Institute of Psychology, Beijing, China
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García-Pardo MP, Roger-Sanchez C, Rodríguez-Arias M, Miñarro J, Aguilar MA. Pharmacological modulation of protein kinases as a new approach to treat addiction to cocaine and opiates. Eur J Pharmacol 2016; 781:10-24. [DOI: 10.1016/j.ejphar.2016.03.065] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 03/28/2016] [Accepted: 03/31/2016] [Indexed: 12/13/2022]
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Harada S, Nakamoto K, Tokuyama S. The involvement of midbrain astrocyte in the development of morphine tolerance. Life Sci 2013; 93:573-8. [DOI: 10.1016/j.lfs.2013.08.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 08/02/2013] [Accepted: 08/13/2013] [Indexed: 01/28/2023]
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Abstract
This paper is the thirty-fourth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2011 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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