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Fu LW, Tjen-A-Looi SC, Barvarz S, Guo ZL, Malik S. Role of opioid receptors in modulation of P2X receptor-mediated cardiac sympathoexcitatory reflex response. Sci Rep 2019; 9:17224. [PMID: 31748569 PMCID: PMC6868205 DOI: 10.1038/s41598-019-53754-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Accepted: 10/31/2019] [Indexed: 01/15/2023] Open
Abstract
Myocardial ischemia evokes powerful reflex responses through activation of vagal and sympathetic afferents in the heart through the release of ischemic metabolites. We have demonstrated that extracellular ATP stimulates cardiac sympathetic afferents through P2 receptor-mediated mechanism, and that opioid peptides suppress these afferents' activity. However, the roles of both P2 receptor and endogenous opioids in cardiac sympathoexcitatory reflex (CSR) responses remain unclear. We therefore hypothesized that activation of cardiac P2 receptor evokes CSR responses by stimulating cardiac sympathetic afferents and these CSR responses are modulated by endogenous opioids. We observed that intrapericardial injection of α,β-methylene ATP (α,β-meATP, P2X receptor agonist), but not ADP (P2Y receptor agonist), caused a graded increase in mean arterial pressure in rats with sinoaortic denervation and vagotomy. This effect of α,β-meATP was abolished by blockade of cardiac neural transmission with intrapericardial procaine treatment and eliminated by intrapericardial A-317491, a selective P2X2/3 and P2X3 receptor antagonist. Intrapericardial α,β-meATP also evoked CSR response in vagus-intact rats. Furthermore, the P2X receptor-mediated CSR responses were enhanced by intrapericardial naloxone, a specific opioid receptor antagonist. These data suggest that stimulation of cardiac P2X2/3 and P2X3, but not P2Y receptors, powerfully evokes CSR responses through activation of cardiac spinal afferents, and that endogenous opioids suppress the P2X receptor-mediated CSR responses.
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Affiliation(s)
- Liang-Wu Fu
- Susan Samueli Integrative Health Institute and Department of Medicine, School of Medicine, University of California at Irvine, Irvine, CA, 92697, USA.
| | - Stephanie C Tjen-A-Looi
- Susan Samueli Integrative Health Institute and Department of Medicine, School of Medicine, University of California at Irvine, Irvine, CA, 92697, USA
| | - Sherwin Barvarz
- Susan Samueli Integrative Health Institute and Department of Medicine, School of Medicine, University of California at Irvine, Irvine, CA, 92697, USA
| | - Zhi-Ling Guo
- Susan Samueli Integrative Health Institute and Department of Medicine, School of Medicine, University of California at Irvine, Irvine, CA, 92697, USA
| | - Shaista Malik
- Susan Samueli Integrative Health Institute and Department of Medicine, School of Medicine, University of California at Irvine, Irvine, CA, 92697, USA
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Fu LW, Longhurst JC. Functional role of peripheral opioid receptors in the regulation of cardiac spinal afferent nerve activity during myocardial ischemia. Am J Physiol Heart Circ Physiol 2013; 305:H76-85. [PMID: 23645463 DOI: 10.1152/ajpheart.00091.2013] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Thinly myelinated Aδ-fiber and unmyelinated C-fiber cardiac sympathetic (spinal) sensory nerve fibers are activated during myocardial ischemia to transmit the sensation of angina pectoris. Although recent observations showed that myocardial ischemia increases the concentrations of opioid peptides and that the stimulation of peripheral opioid receptors inhibits chemically induced visceral and somatic nociception, the role of opioids in cardiac spinal afferent signaling during myocardial ischemia has not been studied. The present study tested the hypothesis that peripheral opioid receptors modulate cardiac spinal afferent nerve activity during myocardial ischemia by suppressing the responses of cardiac afferent nerve to ischemic mediators like bradykinin and extracellular ATP. The nerve activity of single unit cardiac afferents was recorded from the left sympathetic chain (T₂-T₅) in anesthetized cats. Forty-three ischemically sensitive afferent nerves (conduction velocity: 0.32-3.90 m/s) with receptive fields in the left and right ventricles were identified. The responses of these afferent nerves to repeat ischemia or ischemic mediators were further studied in the following protocols. First, epicardial administration of naloxone (8 μmol), a nonselective opioid receptor antagonist, enhanced the responses of eight cardiac afferent nerves to recurrent myocardial ischemia by 62%, whereas epicardial application of vehicle (PBS) did not alter the responses of seven other cardiac afferent nerves to ischemia. Second, naloxone applied to the epicardial surface facilitated the responses of seven cardiac afferent nerves to epicardial ATP by 76%. Third, administration of naloxone enhanced the responses of seven other afferent nerves to bradykinin by 85%. In contrast, in the absence of naloxone, cardiac afferent nerves consistently responded to repeated application of ATP (n = 7) or bradykinin (n = 7). These data suggest that peripheral opioid peptides suppress the responses of cardiac sympathetic afferent nerves to myocardial ischemia and ischemic mediators like ATP and bradykinin.
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Affiliation(s)
- Liang-Wu Fu
- Department of Medicine, School of Medicine, University of California, Irvine, CA 92697, USA.
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Davis MP. Drug management of visceral pain: concepts from basic research. PAIN RESEARCH AND TREATMENT 2012; 2012:265605. [PMID: 22619712 PMCID: PMC3348642 DOI: 10.1155/2012/265605] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Accepted: 02/13/2012] [Indexed: 12/24/2022]
Abstract
Visceral pain is experienced by 40% of the population, and 28% of cancer patients suffer from pain arising from intra- abdominal metastasis or from treatment. Neuroanatomy of visceral nociception and neurotransmitters, receptors, and ion channels that modulate visceral pain are qualitatively or quantitatively different from those that modulate somatic and neuropathic pain. Visceral pain should be recognized as distinct pain phenotype. TRPV1, Na 1.8, and ASIC3 ion channels and peripheral kappa opioid receptors are important mediators of visceral pain. Mu agonists, gabapentinoids, and GABAB agonists reduce pain by binding to central receptors and channels. Combinations of analgesics and adjuvants in animal models have supra-additive antinociception and should be considered in clinical trials. This paper will discuss the neuroanatomy, receptors, ion channels, and neurotransmitters important to visceral pain and provide a basic science rationale for analgesic trials and management.
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Affiliation(s)
- Mellar P. Davis
- Cleveland Clinic Lerner School of Medicine, Case Western Reserve University, Cleveland, OH 44195, USA
- Solid Tumor Division, Harry R. Horvitz Center for Palliative Medicine, Taussig Cancer Institute, USA
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Experimental models of visceral pain. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2010; 617:115-54. [PMID: 20336418 DOI: 10.1007/978-1-60327-323-7_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Visceral pain models are used to study afferent nerve traffic during noxious stimulation at the level of the visceral organ. This chapter provides details on several in vitro and in vivo models of organs in the gastrointestinal and genitourinary tract that use electrophysiological recordings of afferent nerve fibres in order to directly characterize stimulus-response relationships. These models can also be used to investigate stimulus-response patterns during physiological (nonpainful) stimulation of the visceral organs or during exposure to pathological stimuli, such as inflammatory mediators during inflammation of the visceral organ.
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Zuberi AR, Townsend L, Patterson L, Zheng H, Berthoud HR. Increased adiposity on normal diet, but decreased susceptibility to diet-induced obesity in mu-opioid receptor-deficient mice. Eur J Pharmacol 2008; 585:14-23. [PMID: 18396272 DOI: 10.1016/j.ejphar.2008.01.047] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Revised: 01/14/2008] [Accepted: 01/21/2008] [Indexed: 01/22/2023]
Abstract
The mu-opioid receptor encoded by the Oprm1 gene plays a crucial role in the mediation of food reward and drug-induced positive reinforcement, but its genetic deletion has been shown to provide food intake-independent, partial protection from diet-induced obesity. We hypothesized that mu-opioid receptor-deficient mice would show an even greater, intake-dependent, resistance to high-fat diet-induced obesity if the diet comprises a sweet component. We generated an F2 population by crossing the heterozygous offspring of homozygous female Oprm1(-/-) mice (on a mixed C57BL/6 and BALB/c genetic background) with male inbred C57BL/6 mice. Groups of genotyped wild-type (WT) and homozygous mutant (KO) males and females were fed either control chow or a high caloric palatable diet consisting of sweet, liquid chocolate-flavored Ensure together with a solid high-fat diet. Food intake, body weight, and body composition was measured over a period of 16 weeks. Unexpectedly, male, and to a lesser extent female, KO mice fed chow for the entire period showed progressively increased body weight and adiposity while eating significantly more chow. In contrast, when exposed to the sweet plus high-fat diet, male, and to a lesser extent female, KO mice gained significantly less body weight and fat mass compared to WT mice when using chow fed counterparts for reference values. Male KO mice consumed 33% less of the sweet liquid diet but increased intake of high-fat pellets, so that total calorie intake was not different from WT animals. These results demonstrate a dissociation of the role of mu-opioid receptors in the control of adiposity for different diets and sex. On a bland diet, normal receptor function appears to confer a slightly catabolic predisposition, but on a highly palatable diet, it confers an anabolic metabolic profile, favoring fat accretion. Because of the complexity of mu-opioid gene regulation and tissue distribution, more selective and targeted approaches will be necessary to fully understand the underlying mechanisms.
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Affiliation(s)
- Aamir R Zuberi
- Functional Genomics, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
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The involvement of the μ-opioid receptor in gastrointestinal pathophysiology: Therapeutic opportunities for antagonism at this receptor. Pharmacol Ther 2008; 117:162-87. [DOI: 10.1016/j.pharmthera.2007.09.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Accepted: 09/25/2007] [Indexed: 12/26/2022]
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Otto B, Mawe GM, Riepl RL. mu-Opiate receptor agonist loperamide blocks bethanechol-induced gallbladder contraction, despite higher cholecystokinin plasma levels in man. Neurogastroenterol Motil 2005; 17:761-6. [PMID: 16185316 DOI: 10.1111/j.1365-2982.2005.00694.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
UNLABELLED mu-Opiate receptor agonists, such as loperamide, influence biliary excretion and suppress cholecystokinin (CCK)-induced gallbladder contraction. Loperamide decreases cholinergic mechanisms, like pancreatic polypeptide (PP) release, while muscarinic agonist (bethanechol)-induced PP release remains unaffected. The effects of loperamide on gallbladder contraction and peptide release were performed to resolve this discrepancy. METHODS Six subjects (27.6 +/- 2.0 years) received bethanechol (12.5, 25 and 50 microg kg(-1) h(-1) continuously over 40 min) after oral 16 mg loperamide (vs placebo) in a crossover design. Gallbladder volume and plasma levels of CCK, PP, motilin, gastrin, neurotensin, cholylglycine were measured regularly. RESULTS Bethanechol significantly reduced gallbladder volume (26.7 +/- 1.9 to a nadir of 15.3 +/- 2.2 mL, P < or = 0.05), and this action was inhibited by loperamide. Basal CCK levels increased significantly after loperamide. Incremental integrated CCK release after bethanechol was higher under loperamide (P < or = 0.05), as placebo CCK release was significantly decreased under bethanechol (2.0 +/- 0.4-0.8 +/- 0.3 pmol L(-1)). In both settings, PP levels were significantly increased after bethanechol, while release of neurotensin, motilin, gastrin and cholylglycine was unaffected. CONCLUSION The mu-opiate receptor agonist loperamide inhibits bethanechol-induced gallbladder contraction. This effect is not mediated by inhibition of CCK release, as loperamide even enhances basal CCK plasma levels. As cholinergic mechanisms, like bethanechol-induced incremental PP release, were unaffected, mu-opiate agonists might influence gallbladder contraction via vagal-cholinergic pathways.
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Affiliation(s)
- B Otto
- Department of Internal Medicine - Innenstadt, University Hospital, Munich, Germany.
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Abstract
Alvimopan is a novel, peripherally acting mu-opioid antagonist that is being developed for the management of acute postoperative ileus and for the reversal of the delayed gastrointestinal and colonic transit that result in symptoms such as constipation, nausea and motility disorders in patients treated with opiate analgesics. There is a clinical need for effective medications for the treatment of postoperative ileus and opiate-induced constipation and other motility disorders. This review addresses the basic and applied pharmacology and current evidence for the use of the medication, alvimopan, in clinical gastroenterology.
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Affiliation(s)
- M Camilleri
- Clinical Enteric Neuroscience Translational and Epidemiological Research (CENTER) Program, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA.
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Greenwood-Van Meerveld B, Gardner CJ, Little PJ, Hicks GA, Dehaven-Hudkins DL. Preclinical studies of opioids and opioid antagonists on gastrointestinal function. Neurogastroenterol Motil 2004; 16 Suppl 2:46-53. [PMID: 15357851 DOI: 10.1111/j.1743-3150.2004.00555.x] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Opioid receptors in the gastrointestinal (GI) tract mediate the effects of endogenous opioid peptides and exogenously administered opioid analgesics, on a variety of physiological functions associated with motility, secretion and visceral pain. The studies reviewed or reported here describe a range of in vivo activities of opioid receptor antagonists upon GI function in rodents, focusing on mu receptors. Naloxone, and the peripherally acting mu-opioid receptor antagonists alvimopan and methylnaltrexone, reverse morphine-induced inhibition of GI transit in mice and rats, and morphine- or loperamide-induced inhibition of castor oil-induced diarrhoea in mice. At doses producing maximal reversal of morphine-induced effects upon GI transit, only the central nervous system (CNS) penetrant antagonist naloxone was able to reverse morphine-induced analgesia. Both central and peripheral opioid antagonists may affect GI function and/or visceromotor sensitivity in the absence of exogenous opioid analgesics, suggesting a constitutive role for endogenous opioid peptides in the control of GI physiology. Furthermore, in contrast to naloxone, alvimopan does not produce hypersensitivity to the visceromotor response induced by nociceptive levels of colorectal distension in a rodent model of post-inflammatory colonic hypersensitivity, suggesting that in the periphery endogenous mu-opioid receptor-mediated mechanisms do not regulate colonic sensitivity. The data support the hypothesis that peripherally acting opioid antagonists may be able to selectively block opioid receptors in the GI tract, thereby preserving normal GI physiology, while not blocking the effects of endogenous opioid peptides or exogenous opioid analgesics in the CNS. These findings suggest that the primary sites of action of mu-opioid agonists with respect to inhibition of GI function are in the periphery, whereas analgesic activity resides primarily in the CNS.
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Affiliation(s)
- B Greenwood-Van Meerveld
- Gastrointestinal Research, Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK 72104, USA.
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Hicks GA, DeHaven-Hudkins DL, Camilleri M. Opiates in the control of gastrointestinal tract function: current knowledge and new avenues for research. Neurogastroenterol Motil 2004; 16 Suppl 2:67-70. [PMID: 15357854 DOI: 10.1111/j.1743-3150.2004.00560.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- G A Hicks
- Neurology and GI Centre of Excellence for Drug Discovery, GlaxoSmithKline Research and Development Limited, Harlow, Essex, UK.
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