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Xu B, Guo Y, Zhang M, Zhang R, Chen D, Zhang Q, Xiao J, Xu K, Li N, Qiu Y, Zhu H, Niu J, Zhang X, Fang Q. Central and peripheral modulation of gastrointestinal transit in mice by DN-9, a multifunctional opioid/NPFF receptor agonist. Neurogastroenterol Motil 2020; 32:e13848. [PMID: 32281198 DOI: 10.1111/nmo.13848] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 02/05/2020] [Accepted: 03/19/2020] [Indexed: 02/06/2023]
Abstract
BACKGROUND The nonapeptide DN-9 functions as a multifunctional agonist to opioid and neuropeptide FF (NPFF) receptors and exhibits antinociceptive effects at the central and peripheral levels. METHODS The effects of DN-9 on small and colonic intestinal transit were evaluated using the upper gastrointestinal (GI) transit test and colonic bead expulsion assay, respectively. Opioid and NPFF receptor antagonists were used to investigate the mechanisms of DN-9-induced GI inhibition. Furthermore, the agonism of the DN-9 analog [Phg9 ]-DN-9 to opioid and NPFF receptors was tested by the cAMP assay. KEY RESULTS Intracerebroventricular administration of DN-9 dose-dependently slowed upper GI transit and colonic expulsion via mu- and kappa-opioid receptors in the brain, independent of the delta-opioid receptor. Similarly, intraperitoneal injection of DN-9 dose-dependently inhibited GI propulsion via the peripheral opioid receptors. DN-9-induced GI transit inhibitions were significantly aggravated by the NPFF receptor antagonist RF9. Moreover, the DN-9 analog [Phg9 ]-DN-9, an agonist at mu-, delta-, and kappa-opioid receptors but not NPFF receptors, inhibited GI more potently than DN-9. In addition, intracerebroventricular NPFF significantly attenuated the central inhibitory effects induced by [Phg9 ]-DN-9 and morphine. However, central and peripheral injections of NPFF or RF9 almost had no significant effects on GI transit by itself. CONCLUSION AND INFERENCES Intracerebroventricular and intraperitoneal administrations of DN-9 inhibit GI transit via opioid receptors in mice by central and peripheral mechanisms, respectively. In addition, the NPFF agonism of DN-9 possesses antiopioid effects on GI transit, which might explain the reduced constipation at the antinociceptive doses.
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Affiliation(s)
- Biao Xu
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Yuanyuan Guo
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Mengna Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Run Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Dan Chen
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Qinqin Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Jian Xiao
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Kangtai Xu
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Ning Li
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Yu Qiu
- Department of Pharmacology and Chemical Biology, Institute of Medical Sciences, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Hanwen Zhu
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Jiandong Niu
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Xiaoyu Zhang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
| | - Quan Fang
- Key Laboratory of Preclinical Study for New Drugs of Gansu Province, and Institute of Physiology, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China
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Holmes GM, Hubscher CH, Krassioukov A, Jakeman LB, Kleitman N. Recommendations for evaluation of bladder and bowel function in pre-clinical spinal cord injury research. J Spinal Cord Med 2019; 43:165-176. [PMID: 31556844 PMCID: PMC7054945 DOI: 10.1080/10790268.2019.1661697] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Objective: In order to encourage the inclusion of bladder and bowel outcome measures in preclinical spinal cord injury (SCI) research, this paper identifies and categorizes 1) fundamental, 2) recommended, 3) supplemental and 4) exploratory sets of outcome measures for pre-clinical assessment of bladder and bowel function with broad applicability to animal models of SCI.Methods: Drawing upon the collective research experience of autonomic physiologists and informed in consultation with clinical experts, a critical assessment of currently available bladder and bowel outcome measures (histological, biochemical, in vivo functional, ex vivo physiological and electrophysiological tests) was made to identify the strengths, deficiencies and ease of inclusion for future studies of experimental SCI.Results: Based upon pre-established criteria generated by the Neurogenic Bladder and Bowel Working Group that included history of use in experimental settings, citations in the literature by multiple independent groups, ease of general use, reproducibility and sensitivity to change, three fundamental measures each for bladder and bowel assessments were identified. Briefly defined, these assessments centered upon tissue morphology, voiding efficiency/volume and smooth muscle-mediated pressure studies. Additional assessment measures were categorized as recommended, supplemental or exploratory based upon the balance between technical requirements and potential mechanistic insights to be gained by the study.Conclusion: Several fundamental assessments share reasonable levels of technical and material investment, including some that could assess bladder and bowel function non-invasively and simultaneously. Such measures used more inclusively across SCI studies would advance progress in this high priority area. When complemented with a few additional investigator-selected study-relevant supplemental measures, they are highly recommended for research programs investigating the efficacy of therapeutic interventions in preclinical animal models of SCI that have a bladder and/or bowel focus.
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Affiliation(s)
- Gregory M. Holmes
- Neural and Behavioral Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA,Correspondence to: Gregory M. Holmes, Neural and Behavioral Sciences, Pennsylvania State University College of Medicine, 500 University Dr., Hershey, PA 17036, USA. ;
| | - Charles H. Hubscher
- Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky, USA,Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, Kentucky, USA
| | - Andrei Krassioukov
- ICORD, University of British Columbia, GF Strong Rehabilitation Centre, Vancouver, Canada
| | - Lyn B. Jakeman
- National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, USA
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Vera G, Girón R, Martín-Fontelles MI, Abalo R. Radiographic dose-dependency study of loperamide effects on gastrointestinal motor function in the rat. Temporal relationship with nausea-like behavior. Neurogastroenterol Motil 2019; 31:e13621. [PMID: 31117152 DOI: 10.1111/nmo.13621] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2019] [Revised: 04/09/2019] [Accepted: 04/24/2019] [Indexed: 02/08/2023]
Abstract
BACKGROUND Loperamide is a potent mu opioid receptor agonist available over the counter to treat diarrhea. Although at therapeutic doses loperamide is devoid of central effects, it may exert them if used at high doses or combined with drugs that increase its systemic and/or central bioavailability. Recently, public health and scientific interest on loperamide has increased due to a growing trend of misuse and abuse, and consequent reports on its toxicity. Our aim was to evaluate in the rat the effects of increasing loperamide doses, with increasing likelihood to induce central effects, on gastrointestinal motor function (including gastric dysmotility and nausea-like behavior). METHODS Male Wistar rats received an intraperitoneal injection of vehicle or loperamide (0.1, 1, or 10 mg kg-1 ). Three sets of experiments were performed to evaluate: (a) central effects (somatic nociceptive thresholds, immobility time, core temperature, spontaneous locomotor activity); (b) general gastrointestinal motility (serial X-rays were taken 0-8 hours after intragastric barium administration and analyzed semiquantitatively, morphometrically, and densitometrically); and (c) bedding intake (a rodent indirect marker of nausea). Animals from sets 1 and 3 were used to evaluate gastric dysmotility ex vivo at 2 and 4 hours after administration, respectively. KEY RESULTS Loperamide significantly induced antinociception, hypothermia, and hypolocomotion (but not catalepsy) at high doses and dose-dependently reduced gastrointestinal motor function, with the intestine exhibiting higher sensitivity than the stomach. Whereas bedding intake occurred early and transiently, gastric dysmotility was much more persistent. CONCLUSIONS AND INFERENCES Our results suggest that loperamide-induced nausea and gastric dysmotility might be temporally dissociated.
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Affiliation(s)
- Gema Vera
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Alcorcón, Spain.,Grupo de Excelencia Investigadora URJC-Banco de Santander-Grupo Multidisciplinar de Investigación y Tratamiento del Dolor (i+DOL), Alcorcón, Spain.,Unidad Asociada I+D+i al Instituto de Química Médica (IQM), Centro Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Rocío Girón
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Alcorcón, Spain.,Grupo de Excelencia Investigadora URJC-Banco de Santander-Grupo Multidisciplinar de Investigación y Tratamiento del Dolor (i+DOL), Alcorcón, Spain.,Unidad Asociada I+D+i al Instituto de Química Médica (IQM), Centro Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - María Isabel Martín-Fontelles
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Alcorcón, Spain.,Grupo de Excelencia Investigadora URJC-Banco de Santander-Grupo Multidisciplinar de Investigación y Tratamiento del Dolor (i+DOL), Alcorcón, Spain.,Unidad Asociada I+D+i al Instituto de Química Médica (IQM), Centro Superior de Investigaciones Científicas (CSIC), Madrid, Spain
| | - Raquel Abalo
- Departamento de Ciencias Básicas de la Salud, Facultad de Ciencias de la Salud, Universidad Rey Juan Carlos, Alcorcón, Spain.,Grupo de Excelencia Investigadora URJC-Banco de Santander-Grupo Multidisciplinar de Investigación y Tratamiento del Dolor (i+DOL), Alcorcón, Spain.,Unidad Asociada I+D+i al Instituto de Química Médica (IQM), Centro Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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Mosińska P, Zielińska M, Fichna J. Expression and physiology of opioid receptors in the gastrointestinal tract. Curr Opin Endocrinol Diabetes Obes 2016; 23:3-10. [PMID: 26702845 DOI: 10.1097/med.0000000000000219] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
PURPOSE OF REVIEW Stimulation of opioid receptors elicits analgesic effect not only in the central nervous system, but also in the gastrointestinal tract, where a high concentration of opioid receptors can be found within the enteric nervous system as well as muscular and immune cells. Along with antinociception, opioid receptors in the stomach and intestine relay signals crucial for secretory and motor gastrointestinal function. RECENT FINDINGS The review focuses on the utility of opioid receptor antagonists, which is generally contributing to the management of postoperative ileus and opioid bowel dysfunction in chronic pain patients nonetheless, opioid receptor antagonists can also be useful in the treatment of irritable bowel syndrome and chronic idiopathic constipation. The study also discusses several antidiarrheal opioid agonists, as well as opioids and opioid mimetics encompassing the concept of ligand-biased agonism and truncated opioid receptor splice variants. SUMMARY Good understanding of the localization and the role of opioid receptors is vital for regulation of various pathophysiological processes in the gastrointestinal tract and may simultaneously provide a tempting approach in eliminating adverse effects related to centrally acting opioids.
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Affiliation(s)
- Paula Mosińska
- Department of Biochemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
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YIN H, CAI HZ, WANG SK, YANG LG, SUN GJ. Wheat peptides reduce oxidative stress and inhibit NO production through modulating μ-opioid receptor in a rat NSAID-induced stomach damage model. Chin J Nat Med 2015; 13:22-9. [DOI: 10.1016/s1875-5364(15)60003-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2014] [Indexed: 12/31/2022]
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Sobczak M, Sałaga M, Storr MA, Fichna J. Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives. J Gastroenterol 2014; 49:24-45. [PMID: 23397116 PMCID: PMC3895212 DOI: 10.1007/s00535-013-0753-x] [Citation(s) in RCA: 133] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Accepted: 01/10/2013] [Indexed: 02/04/2023]
Abstract
Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.
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Affiliation(s)
- Marta Sobczak
- Department of Biomolecular Chemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland
| | - Maciej Sałaga
- Department of Biomolecular Chemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland
| | - Martin A. Storr
- Division of Gastroenterology, Department of Medicine, Ludwig Maximilians University of Munich, Munich, Germany
| | - Jakub Fichna
- Department of Biomolecular Chemistry, Faculty of Medicine, Medical University of Lodz, Mazowiecka 6/8, 92-215 Lodz, Poland
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Fichna J, Socała K, Nieoczym D, Gach K, Perlikowska R, Janecka A, Wlaź P. The mu-opioid receptor-selective peptide antagonists, antanal-1 and antanal-2, produce anticonvulsant effects in mice. Prog Neuropsychopharmacol Biol Psychiatry 2013; 40:126-31. [PMID: 22918032 DOI: 10.1016/j.pnpbp.2012.07.020] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Revised: 07/25/2012] [Accepted: 07/26/2012] [Indexed: 10/28/2022]
Abstract
The activation of the mu-opioid receptors (MOR) in the central nervous system has a proconvulsant effect and seizures are a common side effect of high doses of short acting opioids, like morphine or fentanyl. However, the correct assessment of the role of MOR blockade in the initiation and propagation of epilepsy was hampered by the lack of potent and selective MOR antagonists. In this study we aimed at characterizing the effect of MOR blockade on the seizure threshold in mice using recently developed selective antagonists antanal-1 and antanal-2 and a classical MOR antagonist, β-funaltrexamine (β-FNA). The effect of the centrally administered MOR antagonists was characterized in the maximal electroshock seizure threshold (MEST), the 6 Hz psychomotor seizure threshold and the intravenous pentylenetetrazole (PTZ) seizure threshold test in mice. The acute effect of the studied compounds on skeletal muscular strength in mice was quantified in the grip-strength test. Antanal-1 and antanal-2 (30 and 50 nmol/mouse, i.c.v.), but not β-FNA significantly increased the seizure threshold in the MEST test in mice. In the 6-Hz test, all tested MOR antagonists significantly increased the psychomotor seizure threshold and the most potent anticonvulsant effect was observed for antanal-2 (2, 10 and 30 nmol/mouse, i.c.v.). The i.c.v. administration of β-FNA (10 and 30 nmol/mouse, i.c.v.), antanal-1 and antanal-2 (both 30, 50 and 100 nmol/mouse, i.c.v.) did not produce any significant effect on PTZ seizure threshold, the generalized clonus or the forelimbs tonus. All tested compounds did not affect muscle strength, as determined in the grip strength test. Our study demonstrated that the novel MOR-selective antagonists antanal-1 and antanal-2 displayed a potent and dose-dependent anticonvulsant action involving non-GABA-ergic, but some other pathways and mechanisms in animal models of epileptic seizures. We suggest that antanals are promising drug templates for future therapeutics, which may be used in the treatment of epilepsy in humans.
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Affiliation(s)
- Jakub Fichna
- Department of Biomolecular Chemistry, Faculty of Medicine, Medical University of Lodz, Lodz, Poland
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Non-specific abdominal pain and air pollution: a novel association. PLoS One 2012; 7:e47669. [PMID: 23118887 PMCID: PMC3485276 DOI: 10.1371/journal.pone.0047669] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2012] [Accepted: 09/18/2012] [Indexed: 12/26/2022] Open
Abstract
Background We studied whether short-term exposure to air pollution was associated with non-specific abdominal pain in epidemiologic and animal studies. Methods Patients visiting the emergency department with non-specific abdominal pain were identified in Edmonton (1992 to 2002, n = 95,173) and Montreal (1997 to 2002, n = 25,852). We calculated the daily concentrations for ozone (O3), nitrogen dioxide (NO2), sulfur dioxide (SO2), carbon monoxide (CO), and particles <10 (PM10) or <2.5 (PM2.5) µm. A case crossover study design was used to estimate the odds ratio (OR) and 95% confidence interval (CI) associated with an increase in the interquartile range of the air pollutants. We investigated differential effects by age and sex. Mice were gavaged with urban particle extracts. In animal models, colonic motility was tested, and visceral abdominal pain was measured using a writhing test, and behavioral response to oil of mustard and neostigmine. Motility and pain was measured acutely (1.5 hours after gavage) and chronically (7-days and 21-days after gavage). Results Emergency department visits for non-specific abdominal pain were primarily by women between the ages of 15–24 years. Individuals aged 15 to 24 years were at increased risk of non-specific abdominal pain in Edmonton (same day CO: OR = 1.04, 95% CI = 1.02–1.06; and NO2: OR = 1.06, 95% CI = 1.03–1.09). The risk of air pollution among 15–24 year olds in Montreal was significantly positive (same day CO: OR = 1.11, 95% CI = 1.05–1.17; NO2: OR = 1.09, 95% CI = 1.01–1.16; SO2: OR = 1.17, 95% CI = 1.10–1.25; PM2.5: OR = 1.09, 95% CI = 1.04–1.15). Abdominal pain was increased by an acute gavage of pollution extract but not to chronic exposure to pollutants. Colonic transit was delayed following chronic but not acute exposure with the pollutants. Conclusions Epidemiological and animal data suggest that short-term exposure to air pollution may trigger non-specific abdominal pain in young individuals.
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Kovács G, Petrovszki Z, Mallareddy J, Tóth G, Benedek G, Horváth G. Characterization of antinociceptive potency of endomorphin-2 derivatives with unnatural amino acids in rats. ACTA ACUST UNITED AC 2012; 99:353-63. [DOI: 10.1556/aphysiol.99.2012.3.12] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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Abstract
This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 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, USA.
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Sauriyal DS, Jaggi AS, Singh N. Extending pharmacological spectrum of opioids beyond analgesia: multifunctional aspects in different pathophysiological states. Neuropeptides 2011; 45:175-88. [PMID: 21208657 DOI: 10.1016/j.npep.2010.12.004] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/20/2010] [Revised: 12/06/2010] [Accepted: 12/07/2010] [Indexed: 11/29/2022]
Abstract
Opioids are well known to exert potent central analgesic actions. In recent years, the numerous studies have unfolded the critical role of opioids in the pathophysiology of various diseases as well as in biological phenomenon of therapeutic interest. The endogenous ligands of opioid receptors are derived from three independent genes and their appropriate processing yields the major representative opioid peptides beta-endorphin, met-enkephalin, leu-enkephalin and dynorphin, respectively. These peptides and their derivatives exhibit different affinity and selectivity for the mu-, delta- and kappa-receptors located on the central and the peripheral neurons, neuroendocrine, immune, and mucosal cells and on many other organ systems. The present review article highlights the role of these peptides in central nervous system disorders such as depression, anxiety, epilepsy, and stress; gastrointestinal disorders such as diarrhea, postoperative ileus, ulceration, and irritable bowel syndrome; immune system and related inflammatory disorders such as osteoarthritis and rheumatoid arthritis; and others including respiratory, alcoholism and obesity/binge eating. Furthermore, the key role of opioids in different forms of pre- and post-conditioning including ischemic and pharmacological along with in remote preconditioning has also been described.
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