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Huang P, Ho CK, Cao D, Inan S, Rawls SM, Li M, Huang B, Pagare PP, Townsend EA, Poklis JL, Halquist MS, Banks M, Zhang Y, Liu-Chen LY. NCP, a dual kappa and mu opioid receptor agonist, is a potent analgesic against inflammatory pain without reinforcing or aversive properties. J Pharmacol Exp Ther 2024; 389:JPET-AR-2023-001870. [PMID: 38409113 PMCID: PMC10949162 DOI: 10.1124/jpet.123.001870] [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: 08/09/2023] [Revised: 01/24/2024] [Accepted: 01/30/2024] [Indexed: 02/28/2024] Open
Abstract
While agonists of mu (MOR) and kappa (KOR) opioid receptors have analgesic effects, they produce euphoria and dysphoria, respectively. Other side effects include respiratory depression and addiction for MOR agonists and sedation for KOR agonists. We reported that 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-{[4'-(2'-cyanopyridyl)]carboxamido}cmorphinan (NCP) displayed potent KOR full agonist and MOR partial agonist activities (58%) with 6.5x KOR-over-MOR selectivity in vitro Herein, we characterized pharmacological effects of NCP in rodents. In mice, NCP exerted analgesic effects against inflammatory pain in both the formalin test and the acetic acid writhing test, with A50 values of 47.6 and 14.4 microg/kg (s.c.), respectively. The analgesic effects in the acetic acid writhing test were mediated by the KOR. NCP at doses much higher than those effective in reducing inflammatory pain did not produce antinociception in the hot plate and tail flick tests, inhibit compound 48/80-induced scratching, cause conditioned place aversion (CPA) or preference, impair rotarod performance, inhibit locomotor activity, cause respiratory depression, or precipitate morphine withdrawal. However, NCP (10~100 microg/kg) inhibited gastrointestinal transit with a maximum of ~40% inhibition. In MOR knockout mice, NCP caused CPA, demonstrating that its lack of CPA is due to combined actions on the MOR and KOR. Following s.c. injection, NCP penetrated into the mouse brain. In rats trained to self-administer heroin, NCP (1~320 microg/kg/infusion) did not function as a reinforcer. Thus, NCP produces potent analgesic effects via KOR without side effects except constipation. Therefore, dual full KOR/partial MOR agonists with moderate KOR-over-MOR selectivity may be promising as non-addictive analgesics for inflammatory pain. Significance Statement Developing non-addictive analgesics is crucial for reducing opioid overdose deaths, minimizing drug misuse, and promoting safer pain management practices. Herein, pharmacology of a potential non-addictive analgesic, NCP, is reported. NCP has full KOR agonist / partial MOR agonist activities with a 6.5 x selectivity for KOR over MOR. Unlike MOR agonists, analgesic doses of NCP do not lead to self-administration or respiratory depression. Furthermore, NCP does not produce aversion, hypolocomotion, or motor incoordination, side effects typically associated with KOR activation.
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Affiliation(s)
- Peng Huang
- Temple University Lewis Katz School of Medicine, United States
| | - Conrad K Ho
- Temple University Lewis Katz School of Medicine, United States
| | - Danni Cao
- Temple University Lewis Katz School of Medicine, United States
| | - Saadet Inan
- Center for Substance Abuse Research, Lewis Katz School of Medicine, Temple University, Lewis Katz School of Medicine, Temple University, United States
| | - Scott M Rawls
- Temple University Lewis Katz School of Medicine, United States
| | - Mengchu Li
- Virginia Commonwealth University School of Pharmacy, United States
| | - Boshi Huang
- Virginia Commonwealth University School of Pharmacy, United States
| | - Piyusha P Pagare
- Virginia Commonwealth University School of Pharmacy, United States
| | | | | | | | - Matthew Banks
- Virginia Commonwealth University School of Medicine, United States
| | - Yan Zhang
- Virginia Commonwealth University School of Pharmacy, United States
| | - Lee-Yuan Liu-Chen
- Center for Substance Abuse Research, Temple University Lewis Katz School of Medicine, United States
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Youngblood B, Li K, Gehlert DR, Medina JC, Schwartz N. A Novel Maintenance Therapeutic for Opioid Use Disorder. J Pharmacol Exp Ther 2021; 378:133-145. [PMID: 34011529 PMCID: PMC8407529 DOI: 10.1124/jpet.120.000214] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 05/17/2021] [Indexed: 12/23/2022] Open
Abstract
Opioid use disorder (OUD) is a major socioeconomic burden. An ideal OUD pharmacotherapy will mitigate the suffering associated with opioid-withdrawal, inhibit the effects of high efficacy opioids, and minimize opioid-cravings while being safe and accessible to a diverse patient population. Although current OUD pharmacotherapies inhibit the euphoric effects of opioids of abuse, the extent to which they safely alleviate withdrawal and opioid-cravings corresponds with their intrinsic µ opioid receptor (MOR) efficacy. In addition to inhibiting the euphoric effects of opioids of abuse, the medium efficacy MOR agonist buprenorphine alleviates withdrawal and opioid-cravings, but its intrinsic MOR efficacy is sufficient such that its utility is limited by abuse and safety liabilities. Although the MOR antagonist naltrexone minimizes euphoria and has no abuse liability, it exacerbates suffering associated with withdrawal and opioid cravings. Therefore, a therapeutic with intrinsic MOR activity between the partial agonist (buprenorphine) and the antagonist (naltrexone) would strike a balance between the benefits and liabilities of these two therapeutics. To address this need, we derived RM1490, an MOR agonist based on a nonmorphinan scaffold that exhibits approximately half the intrinsic MOR efficacy of buprenorphine. In a series of preclinical assays, we compared RM1490 with buprenorphine and naltrexone at doses that achieve therapeutic levels of central nervous system MOR occupancy. RM1490 exhibited a behavioral profile consistent with reduced reward, dependence, and precipitated withdrawal liabilities. RM1490 was also more effective than buprenorphine at reversing the respiratory depressant effects of fentanyl and did not suppress respiration when combined with diazepam. SIGNIFICANCE STATEMENT: In preclinical studies, RM1490 has a physiological and behavioral profile suitable for opioid use disorder maintenance therapy.
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Affiliation(s)
- Beth Youngblood
- Epiodyne Inc., San Francisco, California (B.Y., D.R.G., J.C.M., N.S.) and R2M Pharma Inc., South San Francisco, California (K.L., J.C.M.)
| | - Kevin Li
- Epiodyne Inc., San Francisco, California (B.Y., D.R.G., J.C.M., N.S.) and R2M Pharma Inc., South San Francisco, California (K.L., J.C.M.)
| | - Donald R Gehlert
- Epiodyne Inc., San Francisco, California (B.Y., D.R.G., J.C.M., N.S.) and R2M Pharma Inc., South San Francisco, California (K.L., J.C.M.)
| | - Julio C Medina
- Epiodyne Inc., San Francisco, California (B.Y., D.R.G., J.C.M., N.S.) and R2M Pharma Inc., South San Francisco, California (K.L., J.C.M.)
| | - Neil Schwartz
- Epiodyne Inc., San Francisco, California (B.Y., D.R.G., J.C.M., N.S.) and R2M Pharma Inc., South San Francisco, California (K.L., J.C.M.)
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Kudla L, Przewlocki R. Influence of G protein-biased agonists of μ-opioid receptor on addiction-related behaviors. Pharmacol Rep 2021; 73:1033-1051. [PMID: 33835467 PMCID: PMC8413226 DOI: 10.1007/s43440-021-00251-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 03/05/2021] [Accepted: 03/16/2021] [Indexed: 01/09/2023]
Abstract
Opioid analgesics remain a gold standard for the treatment of moderate to severe pain. However, their clinical utility is seriously limited by a range of adverse effects. Among them, their high-addictive potential appears as very important, especially in the context of the opioid epidemic. Therefore, the development of safer opioid analgesics with low abuse potential appears as a challenging problem for opioid research. Among the last few decades, different approaches to the discovery of novel opioid drugs have been assessed. One of the most promising is the development of G protein-biased opioid agonists, which can activate only selected intracellular signaling pathways. To date, discoveries of several biased agonists acting via μ-opioid receptor were reported. According to the experimental data, such ligands may be devoid of at least some of the opioid side effects, such as respiratory depression or constipation. Nevertheless, most data regarding the addictive properties of biased μ-opioid receptor agonists are inconsistent. A global problem connected with opioid abuse also requires the search for effective pharmacotherapy for opioid addiction, which is another potential application of biased compounds. This review discusses the state-of-the-art on addictive properties of G protein-biased μ-opioid receptor agonists as well as we analyze whether these compounds can diminish any symptoms of opioid addiction. Finally, we provide a critical view on recent data connected with biased signaling and its implications to in vivo manifestations of addiction.
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Affiliation(s)
- Lucja Kudla
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology Polish Academy of Sciences, ul. Smetna 12, 31-343, Krakow, Poland
| | - Ryszard Przewlocki
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology Polish Academy of Sciences, ul. Smetna 12, 31-343, Krakow, Poland.
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Co-administration of nalbuphine attenuates the morphine-induced anxiety and dopaminergic alterations in morphine-withdrawn rats. Psychopharmacology (Berl) 2021; 238:1193-1211. [PMID: 33655408 DOI: 10.1007/s00213-021-05765-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 01/12/2021] [Indexed: 10/22/2022]
Abstract
INTRODUCTION The classical effects of exogenous opioids, such as morphine, are predominantly mediated through μ-opioid receptors. The chronic use of morphine induces anxiety-like behavior causing functional changes in the mesolimbic dopaminergic system. The mixed μ/κ-agonist, nalbuphine, used either as an analgesic or as an adjuvant with morphine, produces different and opposite effects. However, whether nalbuphine can be used to antagonize morphine-induced anxiety and dopaminergic alterations is not fully known. OBJECTIVE This study aimed to compare acute and chronic effects of nalbuphine on morphine-induced anxiety and dopaminergic alterations in rats. METHODS Male adult Wistar albino rats were made opioid-dependent by administering increasing doses of morphine (5-25 mg/kg; i.p.; b.i.d.). Withdrawal was induced by naloxone (1 mg/kg, i.p.), 4 h after the last morphine injection. Anxiety-like behavior was measured using Activity Monitor (Coulbourn Instruments, Inc. USA). Thereafter, the animals were sacrificed and the brain dissected out and the level of cAMP and the transcriptional and translational expression of TH was measured. Nalbuphine was co-administered with morphine, acutely and chronically, at various doses (0.1, 0.3, 1.0, 3.0 mg/kg, i.p.). RESULTS Morphine-dependent rats showed a significant higher anxiety and cAMP levels and a significant decrease in the expression of TH. Co-administration of chronic doses of nalbuphine attenuates the higher anxiety, cAMP levels, and upregulates the TH expressions; however, the acute nalbuphine treatment does not attenuate the morphine-induced side effects. CONCLUSION Therefore, nalbuphine might have an important role in attenuating the anxiety and the effects of the dopaminergic pathway and may have potential in the treatment of opioid addiction.
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Kaski SW, White AN, Gross JD, Siderovski DP. Potential for Kappa-Opioid Receptor Agonists to Engineer Nonaddictive Analgesics: A Narrative Review. Anesth Analg 2021; 132:406-419. [PMID: 33332902 DOI: 10.1213/ane.0000000000005309] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A serious adverse effect of prescription opioid analgesics is addiction, both to these analgesics and to illicit drugs like heroin that also activate the µ-opioid receptor (MOR). Opioid use disorder (OUD) and opioid overdose deaths represent a current American health crisis, and the prescription of opioid analgesics has contributed significantly to this crisis. While prescription opioids are highly effective analgesics, there currently exists no facile way to use them for extended periods without the risk of addiction. If addiction caused by MOR-targeting analgesics could be blocked by blending in a new "antiaddiction" ingredient that does not diminish analgesia and does not introduce its own therapeutically limiting side effects, then continued clinical use of prescription opioids for treating pain could be maintained (or even enhanced) instead of curtailed. In this narrative review, we contextualize this hypothesis, first with a brief overview of the current American opioid addiction crisis. The neurobiology of 2 key receptors in OUD development, MOR and the κ-opioid receptor (KOR), is then discussed to highlight the neuroanatomical features and circuitry in which signal transduction from these receptors lie in opposition-creating opportunities for pharmacological intervention in curtailing the addictive potential of MOR agonism. Prior findings with mixed MOR/KOR agonists are considered before exploring new potential avenues such as biased KOR agonists. New preclinical data are highlighted, demonstrating that the G protein-biased KOR agonist nalfurafine reduces the rewarding properties of MOR-targeting analgesics and enhances MOR-targeting analgesic-induced antinociception. Finally, we discuss the recent discovery that a regulator of G protein signaling (namely, RGS12) is a key component of signaling bias at KOR, presenting another drug discovery target toward identifying a single agent or adjuvant to be added to traditional opioid analgesics that could reduce or eliminate the addictive potential of the latter drug.
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Affiliation(s)
- Shane W Kaski
- From the Departments of Neuroscience and Behavioral Medicine & Psychiatry, West Virginia University, Morgantown, West Virginia
| | - Allison N White
- From the Departments of Neuroscience and Behavioral Medicine & Psychiatry, West Virginia University, Morgantown, West Virginia
| | - Joshua D Gross
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina
| | - David P Siderovski
- Department of Pharmacology & Neuroscience, University of North Texas Health Science Center, Fort Worth, Texas
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Kudla L, Bugno R, Skupio U, Wiktorowska L, Solecki W, Wojtas A, Golembiowska K, Zádor F, Benyhe S, Buda S, Makuch W, Przewlocka B, Bojarski AJ, Przewlocki R. Functional characterization of a novel opioid, PZM21, and its effects on the behavioural responses to morphine. Br J Pharmacol 2019; 176:4434-4445. [PMID: 31347704 DOI: 10.1111/bph.14805] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 07/15/2019] [Accepted: 07/16/2019] [Indexed: 01/04/2023] Open
Abstract
BACKGROUND AND PURPOSE The concept of opioid ligands biased towards the G protein pathway with minimal recruitment of β-arrestin-2 is a promising approach for the development of novel, efficient, and potentially nonaddictive opioid therapeutics. A recently discovered biased μ-opioid receptor agonist, PZM21, showed analgesic effects with reduced side effects. Here, we aimed to further investigate the behavioural and biochemical properties of PZM21. EXPERIMENT APPROACH We evaluated antinociceptive effects of systemic and intrathecal PZM21 administration. Its addiction-like properties were determined using several behavioural approaches: conditioned place preference, locomotor sensitization, precipitated withdrawal, and self-administration. Also, effects of PZM21 on morphine-induced antinociception, tolerance, and reward were assessed. Effects of PZM21 on striatal release of monoamines were evaluated using brain microdialysis. KEY RESULTS PZM21 caused long-lasting dose-dependent antinociception. It did not induce reward- and reinforcement-related behaviour; however, its repeated administration led to antinociceptive tolerance and naloxone-precipitated withdrawal symptoms. Pretreatment with PZM21 enhanced morphine-induced antinociception and attenuated the expression of morphine reward. In comparison to morphine, PZM21 administration induced a moderate release of dopamine and a robust release of 5-HT in the striatum. CONCLUSIONS AND IMPLICATIONS PZM21 exhibited antinociceptive efficacy, without rewarding or reinforcing properties. However, its clinical application may be restricted, as it induces tolerance and withdrawal symptoms. Notably, its ability to diminish morphine reward implies that PZM21 may be useful in treatment of opioid use disorders.
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Affiliation(s)
- Lucja Kudla
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Ryszard Bugno
- Department of Medicinal Chemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Urszula Skupio
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Lucja Wiktorowska
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Wojciech Solecki
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Adam Wojtas
- Department of Pharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Krystyna Golembiowska
- Department of Pharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Ferenc Zádor
- Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Sándor Benyhe
- Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, Szeged, Hungary
| | - Szymon Buda
- Department of Organic Chemistry, Faculty of Chemistry, Jagiellonian University, Krakow, Poland
| | - Wioletta Makuch
- Department of Pain Pharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Barbara Przewlocka
- Department of Pain Pharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Andrzej J Bojarski
- Department of Medicinal Chemistry, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
| | - Ryszard Przewlocki
- Department of Molecular Neuropharmacology, Maj Institute of Pharmacology, Polish Academy of Sciences, Krakow, Poland
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7
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Kaski SW, White AN, Gross JD, Trexler KR, Wix K, Harland AA, Prisinzano TE, Aubé J, Kinsey SG, Kenakin T, Siderovski DP, Setola V. Preclinical Testing of Nalfurafine as an Opioid-sparing Adjuvant that Potentiates Analgesia by the Mu Opioid Receptor-targeting Agonist Morphine. J Pharmacol Exp Ther 2019; 371:487-499. [PMID: 31492823 DOI: 10.1124/jpet.118.255661] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 07/16/2019] [Indexed: 01/11/2023] Open
Abstract
Mu opioid receptor (MOR)-targeting analgesics are efficacious pain treatments, but notorious for their abuse potential. In preclinical animal models, coadministration of traditional kappa opioid receptor (KOR)-targeting agonists with MOR-targeting analgesics can decrease reward and potentiate analgesia. However, traditional KOR-targeting agonists are well known for inducing antitherapeutic side effects (psychotomimesis, depression, anxiety, dysphoria). Recent data suggest that some functionally selective, or biased, KOR-targeting agonists might retain the therapeutic effects of KOR activation without inducing undesirable side effects. Nalfurafine, used safely in Japan since 2009 for uremic pruritus, is one such functionally selective KOR-targeting agonist. Here, we quantify the bias of nalfurafine and several other KOR agonists relative to an unbiased reference standard (U50,488) and show that nalfurafine and EOM-salvinorin-B demonstrate marked G protein-signaling bias. While nalfurafine (0.015 mg/kg) and EOM-salvinorin-B (1 mg/kg) produced spinal antinociception equivalent to 5 mg/kg U50,488, only nalfurafine significantly enhanced the supraspinal analgesic effect of 5 mg/kg morphine. In addition, 0.015 mg/kg nalfurafine did not produce significant conditioned place aversion, yet retained the ability to reduce morphine-induced conditioned place preference in C57BL/6J mice. Nalfurafine and EOM-salvinorin-B each produced robust inhibition of both spontaneous and morphine-stimulated locomotor behavior, suggesting a persistence of sedative effects when coadministered with morphine. Taken together, these findings suggest that nalfurafine produces analgesic augmentation, while also reducing opioid-induced reward with less risk of dysphoria. Thus, adjuvant administration of G protein-biased KOR agonists like nalfurafine may be beneficial in enhancing the therapeutic potential of MOR-targeting analgesics, such as morphine.
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Affiliation(s)
- Shane W Kaski
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Allison N White
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Joshua D Gross
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Kristen R Trexler
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Kim Wix
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Aubrie A Harland
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Thomas E Prisinzano
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Jeffrey Aubé
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Steven G Kinsey
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Terry Kenakin
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - David P Siderovski
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
| | - Vincent Setola
- Departments of Physiology and Pharmacology (S.W.K., A.N.W., J.D.G., K.W., D.P.S., V.S.), Neuroscience, and Behavioral Medicine and Psychiatry (V.S.), West Virginia University School of Medicine, Morgantown, West Virginia; Department of Psychology, West Virginia University Eberly College of Arts and Sciences, Morgantown, West Virginia (K.R.T., S.G.K.); Department of Medicinal Chemistry, The University of Kansas School of Pharmacy, Lawrence, Kansas (T.E.P.); Division of Chemical Biology and Medicinal Chemistry, The University of North Carolina Eshelman School of Pharmacy, Chapel Hill, North Carolina (A.A.H., J.A.); and Department of Pharmacology, The University of North Carolina School of Medicine, Chapel Hill, North Carolina (T.K.)
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8
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Chronic co-administration of nalbuphine attenuates the development of opioid dependence. Pharmacol Biochem Behav 2018; 175:130-138. [DOI: 10.1016/j.pbb.2018.10.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 09/29/2018] [Accepted: 10/01/2018] [Indexed: 01/21/2023]
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9
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Roversi K, Pase CS, Roversi K, Vey LT, Dias VT, Metz VG, Burger ME. Trans fat intake across gestation and lactation increases morphine preference in females but not in male rats: Behavioral and biochemical parameters. Eur J Pharmacol 2016; 788:210-217. [DOI: 10.1016/j.ejphar.2016.06.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 06/08/2016] [Accepted: 06/20/2016] [Indexed: 10/21/2022]
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10
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Abdel-Ghany R, Nabil M, Abdel-Aal M, Barakat W. Nalbuphine could decrease the rewarding effect induced by tramadol in mice while enhancing its antinociceptive activity. Eur J Pharmacol 2015; 758:11-5. [PMID: 25843409 DOI: 10.1016/j.ejphar.2015.03.062] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2014] [Revised: 03/24/2015] [Accepted: 03/25/2015] [Indexed: 01/08/2023]
Abstract
Nalbuphine, a kappa-opioid agonist and mu-opioid partial agonist, has been used as an analgesic or an adjuvant with morphine to attenuate the development of morphine dependence and rewarding effect. In this study, we investigated the effect of nalbuphine on tramadol rewarding effect and antinociception. Using the conditioned place preference (CPP) paradigm in mice, we demonstrated that co-administration of nalbuphine (7mg/kg, s.c.) with tramadol (70mg/kg, s.c.) during conditioning completely blocked the CPP induced by tramadol. Co-administration of nalbuphine blocked the increase in dopamine level in the nucleus accumbens induced by tramadol. These actions were accompanied by an increase rather than attenuation of the antinociceptive effect of tramadol. These results suggest that nalbuphine could have a great potential as a pharmacotherapy for tramadol abuse.
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Affiliation(s)
- Rasha Abdel-Ghany
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Egypt
| | - Mahmoud Nabil
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Egypt
| | - Mohamed Abdel-Aal
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Egypt
| | - Waleed Barakat
- Department of Pharmacology and Toxicology, Faculty of Pharmacy, Zagazig University, Egypt; Department of Pharmacology and Toxicology, Faculty of Pharmacy, Tabuk University, Saudi Arabia.
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11
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Abstract
Efficient and safe pediatric perioperative pain therapy in the context of a multimodal pain therapy concept requires a slight to moderate opioid analgesic. Nalbuphine is a nearly ideal opioid for this purpose due to its unique pharmacological properties as a μ-receptor antagonist/κ-receptor agonist and a high safety profile. Nalbuphine is used clinically primarily in postoperative pain therapy administered as a bolus, continuous infusion and patient-controlled analgesia. Furthermore, it is administered in different regimens for pediatric diagnostic and interventional sedation.
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Affiliation(s)
- A-M Schultz-Machata
- Universitätsklinik für Anästhesie, Allgemeine Intensivmedizin und Schmerztherapie, Klinische Abteilung für allgemeine Anästhesie und Intensivmedizin, Medizinische Universität Wien, 1090, Wien, Österreich,
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12
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Effects of combined opioids on pain and mood in mammals. PAIN RESEARCH AND TREATMENT 2012; 2012:145965. [PMID: 22550575 PMCID: PMC3324919 DOI: 10.1155/2012/145965] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 01/02/2012] [Indexed: 11/22/2022]
Abstract
The authors review the opioid literature for evidence of increased analgesia and reduced adverse side effects by combining mu-opioid-receptor (MOR) agonists, kappa-opioid-receptor (KOR) agonists, and nonselective low-dose-opioid antagonists (LD-Ant). We tested fentanyl (MOR agonist) and spiradoline (KOR agonist), singly and combined, against somatic and visceral pain models. Combined agonists induced additive analgesia in somatic pain and synergistic analgesia in visceral pain. Other investigators report similar effects and reduced tolerance and dependence with combined MOR agonist and KOR agonist. LD-Ant added to either a MOR agonist or KOR agonist markedly enhanced analgesia of either agonist. In accordance with other place-conditioning (PC) studies, our PC investigations showed fentanyl-induced place preference (CPP) and spiradoline-induced place aversion (CPA). We reduced fentanyl CPP with a low dose of spiradoline and reduced spiradoline CPA with a low dose of fentanyl. We propose combined MOR agonist, KOR agonist, and LD-Ant to produce superior analgesia with reduced adverse side effects, particularly for visceral pain.
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13
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Han J, Cui C, Wu L. Acupuncture-related techniques for the treatment of opiate addiction: a case of translational medicine. Front Med 2011; 5:141-50. [PMID: 21695618 DOI: 10.1007/s11684-011-0136-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2011] [Accepted: 04/11/2011] [Indexed: 11/27/2022]
Abstract
Drug addiction is a chronic brain disorder characterized by withdrawal symptoms that occur during drug abstinence and a high tendency of relapse. Compared with the currently available pharmacological interventions, acupuncture therapy has the potential to help drug addicts stay away from drugs without major adverse side effects. It has taken decades of research to optimize the parameters of electrical acupoint stimulation for detoxification and for relapse prevention, as well as to establish a safe and easy procedure by which drug addicts can use it on themselves. The discovery that acupuncture can trigger the release of opioid substances from the brain in the 1970s provided the inspiration. Following this, basic research on animals made it possible to understand the mechanisms of action and establish the procedure for treating drug addictions. This article reviews the past, present, and foreseeable future regarding the use of acupuncture-related technique for the treatment of opiate addiction from the perspective of translational medicine.
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Affiliation(s)
- Jisheng Han
- Neuroscience Research Institute, Peking University, Beijing 100191, China.
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14
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Rech RH, Briggs SL, Mokler DJ. Fentanyl and Spiradoline Interactions in a Place-Conditioning Black-White Shuttle-Box. Pharmaceuticals (Basel) 2010. [PMCID: PMC4052544 DOI: 10.3390/ph401101] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Rats were trained for multiple sessions in a place-conditioning shuttle-box to explore motivational interactions of mu and kappa opioid agonists, specifically fentanyl reward and spiradoline aversion. In Phase 1, groups of rats received various doses of mu or kappa agonists, or placebo, testing for preference or aversion. Group A always received saline SC before 15-minute sessions. Group B received fentanyl SC (0.003, 0.006, 0.012 mg/kg), Group C received low and medium doses of agonists SC, and Group D received spiradoline (0.3, 0.6, 1.2 mg/kg) SC during Training Sessions 1-4, rats being restricted to the drug-associated compartment. Rats received saline when restricted to the placebo-associate compartment and on test days with access to both shuttle-box compartments. In Phase 2 of the study, Training Session 5, Combinations of mu and kappa agonists were substituted in Groups B, C, and D. Dose-related preference to fentanyl and aversion to spiradoline occurred during Test Sessions 1-4. During Test Session 5, fentanyl preference in Group B was suppressed by spiradoline, rats in Group C had a saline-like response to combined agonists, and spiradoline aversion in Group D was attenuated by fentanyl. These findings suggest that combined doses of mu and kappa agonists, while additive for antinociception, offset the rewarding and punishing effects of each other.
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Affiliation(s)
- Richard H. Rech
- Department of Pharmacology/Toxicology, Michigan State University, East Lansing, MI 48824, USA; E-Mail: (R.H.R.)
| | - Shannon L. Briggs
- Department of Environmental Quality, State of Michigan, Lansing, MI 48909, USA; E-Mail: (S.L.B.)
| | - David J. Mokler
- Department of Biomedical Sciences, College of Osteopathic Medicine, University of New England, 11 Hills Beach Road, Biddeford, ME 04005, USA
- Author to whom correspondence should be addresses: E-Mail: ; Tel.: +1-207-602-2210; Fax: +1-207-60205931
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15
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Huber R, Panksepp JB, Nathaniel T, Alcaro A, Panksepp J. Drug-sensitive reward in crayfish: an invertebrate model system for the study of SEEKING, reward, addiction, and withdrawal. Neurosci Biobehav Rev 2010; 35:1847-53. [PMID: 21182861 DOI: 10.1016/j.neubiorev.2010.12.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2010] [Accepted: 12/14/2010] [Indexed: 11/17/2022]
Abstract
In mammals, rewarding properties of drugs depend on their capacity to activate appetitive motivational states. With the underlying mechanisms strongly conserved in evolution, invertebrates have recently emerged as a powerful new model in addiction research. In crayfish natural reward has proven surprisingly sensitive to human drugs of abuse, opening an unlikely avenue of research into the basic biological mechanisms of drug addiction. In a series of studies we first examined the presence of natural reward systems in crayfish, then characterized its sensitivity to a wide range of human drugs of abuse. A conditioned place preference (CPP) paradigm was used to demonstrate that crayfish seek out those environments that had previously been paired with the psychostimulants cocaine and amphetamine, and the opioid morphine. The administration of amphetamine exerted its effects at a number of sites, including the stimulation of circuits for active exploratory behaviors (i.e., SEEKING). A further study examined morphine-induced reward, extinction and reinstatement in crayfish. Repeated intra-circulatory infusions of morphine served as a reward when paired with distinct visual or tactile cues. Morphine-induced CPP was extinguished after repeated saline injections. Following this extinction phase, morphine-experienced crayfish were once again challenged with the drug. The priming injections of morphine reinstated CPP at all tested doses, suggesting that morphine-induced CPP is unrelenting. In an exploration of drug-associated behavioral sensitization in crayfish we concurrently mapped measures of locomotion and rewarding properties of morphine. Single and repeated intra-circulatory infusions of morphine resulted in persistent locomotory sensitization, even 5 days following the infusion. Moreover, a single dose of morphine was sufficient to induce long-term behavioral sensitization. CPP for morphine and context-dependent cues could not be disrupted over a drug free period of 5 days. This work demonstrates that crayfish offer a comparative and complementary approach in addiction research. Serving as an invertebrate animal model for the exposure to mammalian drugs of abuse, modularly organized and experimentally accessible nervous systems render crayfish uniquely suited for studying (1) the basic biological mechanisms of drug effects, (2) to explore how the appetitive/seeking disposition is implemented in a simple neural system, and (3) how such a disposition is related to the rewarding action of drugs of abuse. This work aimed to contribute an evolutionary, comparative context to our understanding of a key component in learning, and of natural reward as an important life-sustaining process.
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Affiliation(s)
- Robert Huber
- J.P. Scott Center for Neuroscience, Mind & Behavior, Department of Biological Sciences, Bowling Green State University, Bowling Green, OH 43403, USA.
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16
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Nathaniel TI, Panksepp J, Huber R. Drug-seeking behavior in an invertebrate system: evidence of morphine-induced reward, extinction and reinstatement in crayfish. Behav Brain Res 2008; 197:331-8. [PMID: 18822319 DOI: 10.1016/j.bbr.2008.08.043] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 08/26/2008] [Accepted: 08/28/2008] [Indexed: 11/15/2022]
Abstract
Several lines of evidence suggest that exploring the neurochemical basis of reward in invertebrate species may provide clues for the fundamental behavioral and neurobiology underpinnings of drug addiction. How the presence of drug-sensitive reward relates to a decrease in drug-seeking behavior and reinstatement of drug-seeking behavior in invertebrate systems is not known. The present study of a conditioned place preference (CPP) paradigm in crayfish (Orconectes rusticus) explores morphine-induced reward, extinction and reinstatement. Repeated intra-circulatory infusions of 2.5 microg/g, 5.0 microg/g and 10.0 microg/g doses of morphine over 5 days serve as a reward when paired with a distinct visual or tactile environment. Morphine-induced CPP was extinguished after repeated saline injections for 5 days in the previously morphine-paired compartment. After the previously established CPP had been eliminated during the extinction phase, morphine-experienced crayfish were challenged with 2.5 microg/g, 5.0 microg/g and 10.0 microg/g, respectively. The priming injections of morphine reinstated CPP in all training doses, suggesting that morphine-induced CPP is unrelenting, and that with time, it can be reinstated by morphine following extinction in an invertebrate model just like in mammals. Together with other recent studies, this work demonstrates the advantage of using crayfish as an invertebrate animal model to investigate the basic biological processes that underline exposure to mammalian drugs of abuse.
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Affiliation(s)
- Thomas I Nathaniel
- J.P. Scott Center for Neuroscience, Mind and Behavior and Department of Biological Sciences Bowling Green State University, USA.
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17
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Peripheral electrical stimulation-induced suppression of morphine-induced CCP in rats: A role for dopamine in the nucleus accumbens. Brain Res 2008; 1212:63-70. [DOI: 10.1016/j.brainres.2008.03.044] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2007] [Revised: 03/17/2008] [Accepted: 03/19/2008] [Indexed: 11/24/2022]
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18
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Abstract
This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 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 neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, CUNY, 65-30 Kissena Blvd., Flushing, NY 11367, United States.
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19
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Tzschentke TM. Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade. Addict Biol 2007; 12:227-462. [PMID: 17678505 DOI: 10.1111/j.1369-1600.2007.00070.x] [Citation(s) in RCA: 1000] [Impact Index Per Article: 58.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Conditioned place preference (CPP) continues to be one of the most popular models to study the motivational effects of drugs and non-drug treatments in experimental animals. This is obvious from a steady year-to-year increase in the number of publications reporting the use this model. Since the compilation of the preceding review in 1998, more than 1000 new studies using place conditioning have been published, and the aim of the present review is to provide an overview of these recent publications. There are a number of trends and developments that are obvious in the literature of the last decade. First, as more and more knockout and transgenic animals become available, place conditioning is increasingly used to assess the motivational effects of drugs or non-drug rewards in genetically modified animals. Second, there is a still small but growing literature on the use of place conditioning to study the motivational aspects of pain, a field of pre-clinical research that has so far received little attention, because of the lack of appropriate animal models. Third, place conditioning continues to be widely used to study tolerance and sensitization to the rewarding effects of drugs induced by pre-treatment regimens. Fourth, extinction/reinstatement procedures in place conditioning are becoming increasingly popular. This interesting approach is thought to model certain aspects of relapse to addictive behavior and has previously almost exclusively been studied in drug self-administration paradigms. It has now also become established in the place conditioning literature and provides an additional and technically easy approach to this important phenomenon. The enormous number of studies to be covered in this review prevented in-depth discussion of many methodological, pharmacological or neurobiological aspects; to a large extent, the presentation of data had to be limited to a short and condensed summary of the most relevant findings.
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Affiliation(s)
- Thomas M Tzschentke
- Grünenthal GmbH, Preclinical Research and Development, Department of Pharmacology, Aachen, Germany.
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