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Fullerton EF, Karom MC, Streicher JM, Young LJ, Murphy AZ. Age-Induced Changes in µ-Opioid Receptor Signaling in the Midbrain Periaqueductal Gray of Male and Female Rats. J Neurosci 2022; 42:6232-6242. [PMID: 35790399 PMCID: PMC9374133 DOI: 10.1523/jneurosci.0355-22.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/08/2022] [Accepted: 04/16/2022] [Indexed: 11/21/2022] Open
Abstract
Opioids have decreased analgesic potency (but not efficacy) in aged rodents compared with adults; however, the neural mechanisms underlying this attenuated response are not yet known. The present study investigated the impact of advanced age and biological sex on opioid signaling in the ventrolateral periaqueductal gray (vlPAG) in the presence of chronic inflammatory pain. Assays measuring µ-opioid receptor (MOR) radioligand binding, GTPγS binding, receptor phosphorylation, cAMP inhibition, and regulator of G-protein signaling (RGS) protein expression were performed on vlPAG tissue from adult (2-3 months) and aged (16-18 months) male and female rats. Persistent inflammatory pain was induced by intraplantar injection of complete Freund's adjuvant (CFA). Adult males exhibited the highest MOR binding potential (BP) and highest G-protein activation (activation efficiency ratio) in comparison to aged males and females (adult and aged). No impact of advanced age or sex on MOR phosphorylation state was observed. DAMGO-induced cAMP inhibition was highest in the vlPAG of adult males compared with aged males and females (adult and aged). vlPAG levels of RGS4 and RGS9-2, critical for terminating G-protein signaling, were assessed using RNAscope. Adult rats (both males and females) exhibited lower levels of vlPAG RGS4 and RGS9-2 mRNA expression compared with aged males and females. The observed age-related reductions in vlPAG MOR BP, G-protein activation efficiency, and cAMP inhibition, along with the observed age-related increases in RGS4 and RGS9-2 vlPAG expression, provide potential mechanisms whereby the potency of opioids is decreased in the aged population.SIGNIFICANCE STATEMENT Opioids have decreased analgesic potency (but not efficacy) in aged rodents compared with adults; however, the neural mechanisms underlying this attenuated response are not yet known. In the present study, we observed age-related reductions in ventrolateral periaqueductal gray (vlPAG) µ-opioid receptor (MOR) binding potential (BP), G-protein activation efficiency, and cAMP inhibition, along with the observed age-related increases in regulator of G-protein signaling (RGS)4 and RGS9-2 vlPAG expression, providing potential mechanisms whereby the potency of opioids is decreased in the aged population. These coordinated decreases in opioid receptor signaling may explain the previously reported reduced potency of opioids to produce pain relief in females and aged rats.
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Affiliation(s)
- Evan F Fullerton
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
| | - Mary C Karom
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
| | - John M Streicher
- Department of Pharmacology, College of Medicine, University of Arizona, Tucson, Arizona 85724
| | - Larry J Young
- Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Anne Z Murphy
- Neuroscience Institute, Georgia State University, Atlanta, Georgia 30303
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Lamberts JT, Traynor JR. Opioid receptor interacting proteins and the control of opioid signaling. Curr Pharm Des 2014; 19:7333-47. [PMID: 23448476 DOI: 10.2174/138161281942140105160625] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Accepted: 02/18/2013] [Indexed: 12/31/2022]
Abstract
Opioid receptors are seven-transmembrane domain receptors that couple to intracellular signaling molecules by activating heterotrimeric G proteins. However, the receptor and G protein do not function in isolation but their activities are modulated by several accessory and scaffolding proteins. Examples include arrestins, kinases, and regulators of G protein signaling proteins. Accessory proteins contribute to the observed potency and efficacy of agonists, but also to the direction of signaling and the phenomenon of biased agonism. This review will present current knowledge of such proteins and how they may provide targets for future drug design.
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Affiliation(s)
| | - John R Traynor
- Department of Pharmacology, University of Michigan Medical School, 1301 MSRB III, 1150 West Medical Center Drive, Ann Arbor, MI 48109-5632, USA.
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3
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Zhao J, Xin X, Xie GX, Palmer PP, Huang YG. Molecular and cellular mechanisms of the age-dependency of opioid analgesia and tolerance. Mol Pain 2012; 8:38. [PMID: 22612909 PMCID: PMC3517334 DOI: 10.1186/1744-8069-8-38] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 05/09/2012] [Indexed: 01/17/2023] Open
Abstract
The age-dependency of opioid analgesia and tolerance has been noticed in both clinical observation and laboratory studies. Evidence shows that many molecular and cellular events that play essential roles in opioid analgesia and tolerance are actually age-dependent. For example, the expression and functions of endogenous opioid peptides, multiple types of opioid receptors, G protein subunits that couple to opioid receptors, and regulators of G protein signaling (RGS proteins) change with development and age. Other signaling systems that are critical to opioid tolerance development, such as N-methyl-D-aspartic acid (NMDA) receptors, also undergo age-related changes. It is plausible that the age-dependent expression and functions of molecules within and related to the opioid signaling pathways, as well as age-dependent cellular activity such as agonist-induced opioid receptor internalization and desensitization, eventually lead to significant age-dependent changes in opioid analgesia and tolerance development.
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Affiliation(s)
- Jing Zhao
- Department of Anesthesia, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100730, China
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4
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Abstract
SummaryAt times providing pain relief in elderly patients can prove troublesome. Their tolerance and perception of pain can differ from that of younger patients, while the incidence of pain is above that found in those of less advanced years.Conventional approaches to providing pain relief can be successful, but the tolerance to the side-effects of those drugs used to provide pain relief can be less. Furthermore, polypharmacy can have implications for the range of analgesic drugs that can be considered. Fortunately there are an increasing range of medicinal products with reduced potential for side-effects that can be considered when treating older patients with pain.
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Terzi D, Stergiou E, King SL, Zachariou V. Regulators of G protein signaling in neuropsychiatric disorders. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:299-333. [PMID: 20374720 DOI: 10.1016/s1877-1173(09)86010-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Regulators of G protein signaling (RGS) comprise a diverse group of about 40 proteins which determine signaling amplitude and duration via modulation of receptor/G protein or receptor/effector coupling. Several members of the RGS family are expressed in the brain, where they have precise roles in regulation of important physiological processes. The unique functions of each RGS can be attributed to its structure, distinct pattern of expression, and regulation, and its preferential interactions with receptors, Galpha subunits and other signaling proteins. Evidence suggests dysfunction of RGS proteins is related to several neuropathological conditions. Moreover, clinical and preclinical work reveals that the efficacy and/or side effects of treatments are highly influenced by RGS activity. This article summarizes findings on RGS proteins in vulnerability to several neuropsychiatric disorders, the mechanism via which RGS proteins control neuronal responses and their potential use as drug targets.
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Affiliation(s)
- Dimitra Terzi
- Department of Pharmacology, Faculty of Medicine, University of Crete, Heraklion 71003, Crete, Greece
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6
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The R7 RGS protein family: multi-subunit regulators of neuronal G protein signaling. Cell Biochem Biophys 2009; 54:33-46. [PMID: 19521673 DOI: 10.1007/s12013-009-9052-9] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 05/27/2009] [Indexed: 01/09/2023]
Abstract
G protein-coupled receptor signaling pathways mediate the transmission of signals from the extracellular environment to the generation of cellular responses, a process that is critically important for neurons and neurotransmitter action. The ability to promptly respond to rapidly changing stimulation requires timely inactivation of G proteins, a process controlled by a family of specialized proteins known as regulators of G protein signaling (RGS). The R7 group of RGS proteins (R7 RGS) has received special attention due to their pivotal roles in the regulation of a range of crucial neuronal processes such as vision, motor control, reward behavior, and nociception in mammals. Four proteins in this group, RGS6, RGS7, RGS9, and RGS11, share a common molecular organization of three modules: (i) the catalytic RGS domain, (ii) a GGL domain that recruits G beta(5), an outlying member of the G protein beta subunit family, and (iii) a DEP/DHEX domain that mediates interactions with the membrane anchor proteins R7BP and R9AP. As heterotrimeric complexes, R7 RGS proteins not only associate with and regulate a number of G protein signaling pathway components, but have also been found to form complexes with proteins that are not traditionally associated with G protein signaling. This review summarizes our current understanding of the biology of the R7 RGS complexes including their structure/functional organization, protein-protein interactions, and physiological roles.
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Chapter 7 Biology and Functions of the RGS9 Isoforms. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 86:205-27. [DOI: 10.1016/s1877-1173(09)86007-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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8
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Jayaraman M, Zhou H, Jia L, Cain MD, Blumer KJ. R9AP and R7BP: traffic cops for the RGS7 family in phototransduction and neuronal GPCR signaling. Trends Pharmacol Sci 2008; 30:17-24. [PMID: 19042037 DOI: 10.1016/j.tips.2008.10.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2008] [Revised: 10/07/2008] [Accepted: 10/09/2008] [Indexed: 10/21/2022]
Abstract
RGS (regulator of G protein signaling) proteins have emerged as crucial regulators, effectors and integrators in G-protein-coupled receptor (GPCR) signaling networks. Many RGS proteins accelerate GTP hydrolysis by Galpha subunits, thereby regulating G protein activity, whereas certain RGS proteins also transduce Galpha signals to downstream targets. Particularly intriguing are members of the RGS7 (R7) family (RGS6, RGS7, RGS9 and RGS11), which heterodimerize with Gbeta5. In Caenorhabditis elegans, R7-Gbeta5 heterodimers regulate synaptic transmission, anesthetic action and behavior. In vertebrates, they regulate vision, postnatal development, working memory and the action of psychostimulants or morphine. Here we highlight R9AP and R7BP, a related pair of recently identified SNARE-like R7-family binding proteins, which regulate intracellular trafficking, expression and function of R7-Gbeta5 heterodimers in retina and brain. Emerging understanding of R7BP and R9AP promises to provide new insights into neuronal GPCR signaling mechanisms relevant to the causes and treatment of neurological disorders.
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Affiliation(s)
- Muralidharan Jayaraman
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110, USA
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9
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Abstract
In the elderly patient, the barriers to effective treatment of pain are substantial. Even the perception of pain may differ from that in those of less advanced years. Of course, many other factors impinge on the presence of, and treatment of, pain in elderly patients. Issues of physical accessibility to treatment, cost of drugs, the presence of coexisting illness, the use of concomitant medication, and even the ability to understand the complaints of the patient who has cognitive impairment are only some of those factors that contribute to the complexity of the situation.
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Affiliation(s)
- Gary McCleane
- Rampark Pain Centre, 2 Rampark, Dromore Road, Lurgan, Northern Ireland BT66 7JH, UK.
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MPTP administration in mice changes the ratio of splice isoforms of fosB and rgs9. Brain Res 2007; 1182:1-10. [PMID: 17936734 DOI: 10.1016/j.brainres.2007.08.080] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2007] [Revised: 08/20/2007] [Accepted: 08/30/2007] [Indexed: 11/22/2022]
Abstract
Most cases of Parkinson's disease (PD) are sporadic, suggesting an environmental influence on individuals affected by this neurodegenerative disorder. Environmental stresses often lead to changes in the regulation of splicing of pre-mRNA transcripts and this may lead to the pathogenesis of the disease. A 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)/probenecid mouse model was used to examine the changes in the splicing of the fosB and rgs9 transcripts. The ratio of DeltafosB/fosB transcript was decreased in the substantia nigra and unchanged in the striatum after acute MPTP treatment. The DeltafosB/fosB transcript ratio decreased initially and then increased in the striatum of chronically MPTP-treated animals due to different degrees of reduction for the splice variants over time, whereas the ratio was unchanged in the substantia nigra. The ratio of rgs9-2/rgs9-1 transcript decreased in the substantia nigra of mice after acute MPTP treatment and increased temporarily in the striatum after chronic MPTP treatment. There was an increase in the DeltaFosB/FosB and RGS9-2/RGS9-1 protein ratios 3 weeks and 3 days post-treatment, respectively, in chronically treated mice. The data indicate that the pattern of splice isoforms of fosB and rgs9 reflects the brain's immediate and long-term responses to the physiological stress associated with Parkinsonism.
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11
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Piñeyro G, Archer-Lahlou E. Ligand-specific receptor states: Implications for opiate receptor signalling and regulation. Cell Signal 2007; 19:8-19. [PMID: 16842969 DOI: 10.1016/j.cellsig.2006.05.026] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2006] [Accepted: 05/29/2006] [Indexed: 10/24/2022]
Abstract
Opiate drugs produce their effects by acting upon G protein coupled receptors (GPCRs) and although they are among the most effective analgesics available, their clinical use is restricted by unwanted side effects such as tolerance, physical dependence, respiratory depression, nausea and constipation. As a class, opiates share a common profile of unwanted effects but there are also significant differences in ligand liability for producing these actions. A growing number of studies show that GPCRs may exist in multiple active states that differ in their signalling and regulatory properties and which may distinctively bind different agonists. In this review we summarize evidence supporting the existence of multiple active conformations for MORs and DORs, analyze information favouring the existence of ligand-specific receptor states and assess how ligand-selective efficacy may contribute to the production of longer lasting, better tolerated opiate analgesics.
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Affiliation(s)
- Graciela Piñeyro
- Département de Pharmacologie, Faculté de Médecine, Université de Montréal, Canada.
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12
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Xie GX, Palmer PP. How regulators of G protein signaling achieve selective regulation. J Mol Biol 2006; 366:349-65. [PMID: 17173929 PMCID: PMC1805491 DOI: 10.1016/j.jmb.2006.11.045] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2006] [Revised: 11/02/2006] [Accepted: 11/10/2006] [Indexed: 11/30/2022]
Abstract
The regulators of G protein signaling (RGS) are a family of cellular proteins that play an essential regulatory role in G protein-mediated signal transduction. There are multiple RGS subfamilies consisting of over 20 different RGS proteins. They are basically the guanosine triphosphatase (GTPase)-accelerating proteins that specifically interact with G protein alpha subunits. RGS proteins display remarkable selectivity and specificity in their regulation of receptors, ion channels, and other G protein-mediated physiological events. The molecular and cellular mechanisms underlying such selectivity are complex and cooperate at many different levels. Recent research data have provided strong evidence that the spatiotemporal-specific expression of RGS proteins and their target components, as well as the specific protein-protein recognition and interaction through their characteristic structural domains and functional motifs, are determinants for RGS selectivity and specificity. Other molecular mechanisms, such as alternative splicing and scaffold proteins, also significantly contribute to RGS selectivity. To pursue a thorough understanding of the mechanisms of RGS selective regulation will be of great significance for the advancement of our knowledge of molecular and cellular signal transduction.
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Affiliation(s)
| | - Pamela Pierce Palmer
- *Corresponding author: Pamela Pierce Palmer, M.D., Ph.D., University of California, San Francisco, Department of Anesthesia and Perioperative Care, 513 Parnassus Avenue, Box 0464, Room S-455, San Francisco, California 94143, USA, Telephone: (415)476-6783, FAX: (415)502-5375, E-mail:
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13
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Ben-Ari S, Toiber D, Sas AS, Soreq H, Ben-Shaul Y. Modulated splicing-associated gene expression in P19 cells expressing distinct acetylcholinesterase splice variants. J Neurochem 2006; 97 Suppl 1:24-34. [PMID: 16635247 DOI: 10.1111/j.1471-4159.2006.03725.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Alternative splicing configurations and acetylcholinesterase (AChE) gene expression are both modified in neurons under stress. However, it is unclear if these phenomena are functionally interrelated. Using a home-made spotted microarray focused on splicing-associated transcripts, we tested the effects of excess 3' splice variants of human AChE on splicing-related gene expression in semi-differentiated neuronal P19 cells. Of the tested transcripts, 17.3% and 20.2% showed modified expression levels (log2 of the ratio<-0.3 or>0.3) in transfected P19 cells overexpressing the stress-inducible AChE-R variant or the synaptic AChE-S protein, respectively. Multiple transcripts encoding serine-arginine rich (SR) and SR-related splicing regulators were suppressed in cells expressing either of these variants, whereas the gene groups including splicing-related helicases and transcripts involved in apoptosis displayed variant-specific changes. Our findings are compatible with the assumption that both neuronal overexpression and alternative splicing of pre-AChE mRNA may be causally involved in initiating global changes in neuronal alternative splicing, causing subsequent modifications in the expression patterns of numerous target genes.
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Affiliation(s)
- Shani Ben-Ari
- Department of Biological Chemistry and Israel Center for Neuronal Computation, The Hebrew University of Jerusalem, Jerusalem, Israel
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14
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Ambrose LM, Gallagher SM, Unterwald EM, Van Bockstaele EJ. Dopamine-D1 and delta-opioid receptors co-exist in rat striatal neurons. Neurosci Lett 2006; 399:191-6. [PMID: 16517070 DOI: 10.1016/j.neulet.2006.02.027] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2005] [Revised: 01/24/2006] [Accepted: 02/02/2006] [Indexed: 11/22/2022]
Abstract
Cocaine's enhancement of dopaminergic neurotransmission in the mesolimbic pathway plays a critical role in the initial reinforcing properties of this drug. However, other neurotransmitter systems are also integral to the addiction process. A large body of data indicates that opioids and dopamine together mediate emotional and reinforced behaviors. In support of this, cocaine-mediated increases in activation of dopamine D1 receptors (D1R) results in a desensitization of delta-opioid receptor (DOR) signaling through adenylyl cyclase (AC) in striatal neurons. To further define cellular mechanisms underlying this effect, the subcellular distribution of DOR and D1R was examined in the rat dorsolateral striatum. Dual immunoperoxidase/gold-silver detection combined with electron microscopy was used to identify DOR and D1R immunoreactivities in the same section of tissue. Semi-quantitative analysis revealed that a subset of dendritic cellular profiles exhibited both DOR and D1R immunoreactivities. Of 198 randomly sampled D1R immunoreactive profiles, 43% contained DOR. Similarly of 165 DOR-labeled cellular profiles, 52% contained D1R. The present data provide ultrastructural evidence for co-existence between DOR and D1R in striatal neurons, suggesting a possible mechanism whereby D1R modulation may alter DOR function.
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Affiliation(s)
- L M Ambrose
- Farber Institute for Neurosciences, Department of Neurosurgery, Thomas Jefferson University, 900 Walnut Street, Suite 417, Philadelphia, PA 19107, USA.
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15
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Kim KS, Palmer PP, Kim KJ. RGS Proteins and Opioid Signaling. Korean J Pain 2006. [DOI: 10.3344/kjp.2006.19.1.8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Affiliation(s)
- Kyung Seon Kim
- Department of Rehabilitation, Yonsei University College of Medicine, Seoul, Korea
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
| | - Pamela Pierce Palmer
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
| | - Ki Jun Kim
- Department of Anesthesia and Perioperative Care, University of California, San Francisco, CA 94143, USA
- Department of Anesthesiology and Pain Medicine, and Anesthesia and Pain Research Institute, Yonsei University College of Medicine, Seoul, Korea
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