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Paudel P, Seong SH, Fauzi FM, Bender A, Jung HA, Choi JS. Establishing GPCR Targets of hMAO Active Anthraquinones from Cassia obtusifolia Linn Seeds Using In Silico and In Vitro Methods. ACS OMEGA 2020; 5:7705-7715. [PMID: 32280914 PMCID: PMC7144155 DOI: 10.1021/acsomega.0c00684] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Accepted: 03/16/2020] [Indexed: 05/08/2023]
Abstract
The present study examines the effect of human monoamine oxidase active anthraquinones emodin, alaternin (=7-hydroxyemodin), aloe-emodin, and questin from Cassia obtusifolia Linn seeds in modulating human dopamine (hD1R, hD3R, and hD4R), serotonin (h5-HT1AR), and vasopressin (hV1AR) receptors that were predicted as prime targets from proteocheminformatics modeling via in vitro cell-based functional assays, and explores the possible mechanisms of action via in silico modeling. Emodin and alaternin showed a concentration-dependent agonist effect on hD3R with EC50 values of 21.85 ± 2.66 and 56.85 ± 4.59 μM, respectively. On hV1AR, emodin and alaternin showed an antagonist effect with IC50 values of 10.25 ± 1.97 and 11.51 ± 1.08 μM, respectively. Interestingly, questin and aloe-emodin did not have any observable effect on hV1AR. Only alaternin was effective in antagonizing h5-HT1AR (IC50: 84.23 ± 4.12 μM). In silico studies revealed that a hydroxyl group at C1, C3, and C8 and a methyl group at C6 of anthraquinone structure are essential for hD3R agonist and hV1AR antagonist effects, as well as for the H-bond interaction of 1-OH group with Ser192 at a proximity of 2.0 Å. Thus, based on in silico and in vitro results, hV1AR, hD3R, and h5-HT1AR appear to be prime targets of the tested anthraquinones.
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Affiliation(s)
- Pradeep Paudel
- Department
of Food and Life Science, Pukyong National
University, Busan 48513, Republic of Korea
| | - Su Hui Seong
- Department
of Food and Life Science, Pukyong National
University, Busan 48513, Republic of Korea
| | - Fazlin Mohd Fauzi
- Department
of Pharmacology and Chemistry, Faculty of Pharmacy, Universiti Teknologi MARA, Selangor Branch, Puncak Alam Campus, 42300 Bandar Puncak Alam, Selangor, Malaysia
| | - Andreas Bender
- Center
for Molecular Science Informatics, Department of Chemistry, University of Cambridge, Lensfield Road, CB2
1EW Cambridge, United Kingdom
| | - Hyun Ah Jung
- Department
of Food Science and Human Nutrition, Jeonbuk
National University, Jeonju 54896, Republic of Korea
- . Tel: 82-63-270-4882. Fax: 82-63-270-3854
| | - Jae Sue Choi
- Department
of Food and Life Science, Pukyong National
University, Busan 48513, Republic of Korea
- . Tel: +82-51-629-5845. Fax: +82-51-629 5842
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Serotonin-1A receptor dependent modulation of pain and reward for improving therapy of chronic pain. Pharmacol Res 2018; 134:212-219. [DOI: 10.1016/j.phrs.2018.06.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 06/12/2018] [Accepted: 06/29/2018] [Indexed: 12/24/2022]
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Gainfully employing descending controls in acute and chronic pain management. Vet J 2018; 237:16-25. [DOI: 10.1016/j.tvjl.2018.05.005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2017] [Revised: 05/15/2018] [Accepted: 05/16/2018] [Indexed: 12/30/2022]
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Donnerer J, Liebmann I. ERK1/2 Phosphorylation in the Rat Supraoptic Nucleus, Dorsal Raphe Nucleus, and Locus Coeruleus Neurons Following Noxious Stimulation to the Hind Paw. Pharmacology 2015; 97:57-62. [DOI: 10.1159/000442211] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 11/05/2015] [Indexed: 11/19/2022]
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Liu Y, Yang L, Yu J, Zhang YQ. Persistent, comorbid pain and anxiety can be uncoupled in a mouse model. Physiol Behav 2015; 151:55-63. [DOI: 10.1016/j.physbeh.2015.07.004] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 07/03/2015] [Accepted: 07/05/2015] [Indexed: 01/26/2023]
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Fujita W, Gomes I, Devi LA. Revolution in GPCR signalling: opioid receptor heteromers as novel therapeutic targets: IUPHAR review 10. Br J Pharmacol 2015; 171:4155-76. [PMID: 24916280 DOI: 10.1111/bph.12798] [Citation(s) in RCA: 64] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 01/27/2014] [Accepted: 04/16/2014] [Indexed: 12/24/2022] Open
Abstract
GPCRs can interact with each other to form homomers or heteromers. Homomers involve interactions with the same receptor type while heteromers involve interactions between two different GPCRs. These receptor-receptor interactions modulate not only the binding but also the signalling and trafficking properties of individual receptors. Opioid receptor heteromerization has been extensively investigated with the objective of identifying novel therapeutic targets that are as potent as morphine but without the side effects associated with chronic morphine use. In this context, studies have described heteromerization between the different types of opioid receptors and between opioid receptors and a wide range of GPCRs including adrenoceptors, cannabinoid, 5-HT, metabotropic glutamate and sensory neuron-specific receptors. Recent advances in the field involving the generation of heteromer-specific reagents (antibodies or ligands) or of membrane-permeable peptides that disrupt the heteromer interaction are helping to elucidate the physiological role of opioid receptor heteromers and the contribution of the partner receptor to the side effects associated with opioid use. For example, studies using membrane-permeable peptides targeting the heteromer interface have implicated μ and δ receptor heteromers in the development of tolerance to morphine, and heteromers of μ and gastrin-releasing peptide receptors in morphine-induced itch. In addition, a number of ligands that selectively target opioid receptor heteromers exhibit potent antinociception with a decrease in the side effects commonly associated with morphine use. In this review, we summarize the latest findings regarding the biological and functional characteristics of opioid receptor heteromers both in vitro and in vivo.
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Affiliation(s)
- Wakako Fujita
- Department of Pharmacology and Systems Therapeutics, Icahn School of Medicine at Mount Sinai, New York, NY, USA
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μ-opioid and 5-HT1A receptors heterodimerize and show signalling crosstalk via G protein and MAP-kinase pathways. Cell Signal 2012; 24:1648-57. [DOI: 10.1016/j.cellsig.2012.04.010] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2012] [Accepted: 04/18/2012] [Indexed: 10/28/2022]
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Peiró A, Climent L, Zapater P, Horga A, Horga J. Ketanserin potentiates morphine-induced antinociception mediated by kappa-receptor activation. Pharmacol Res 2011; 64:80-4. [DOI: 10.1016/j.phrs.2011.02.009] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2010] [Revised: 02/24/2011] [Accepted: 02/27/2011] [Indexed: 10/18/2022]
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Aira Z, Buesa I, Salgueiro M, Bilbao J, Aguilera L, Zimmermann M, Azkue JJ. Subtype-specific changes in 5-HT receptor-mediated modulation of C fibre-evoked spinal field potentials are triggered by peripheral nerve injury. Neuroscience 2010; 168:831-41. [PMID: 20412834 DOI: 10.1016/j.neuroscience.2010.04.032] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 03/18/2010] [Accepted: 04/15/2010] [Indexed: 10/19/2022]
Abstract
Neurotransmitter serotonin (5-HT) released from descending pain modulation pathways to the dorsal horn is crucial to spinal nociception processing. This study sought to gain insight into the modulatory roles of specific serotonin receptor subtypes in experimentally induced neuropathic pain. In rats subjected to spinal nerve ligation (SNL) surgery, we recorded field potentials evoked in the spinal dorsal horn by C fibre-input, during spinal superfusion with subtype-selective drugs. In neuropathic rats, subtype 5-HT1A agonist 8-OH-DPAT (100 nM) was found to potently depress evoked field potentials, as opposed to 5-HT2A or 5-HT2B subtype agonists TCB-2 (100 nM) or BW 723C86 (1 microM), respectively, which consistently enhanced evoked potentials. All three failed to alter spinal field potentials in sham operated rats. CP 94253 (1 microM), WAY 161503 (1 mM) or SR 57227 (at 1 microM in SNL rats, and 100 microM in sham rats), selective agonists for 5-HT1B, 5-HT2C and 5-HT3 receptors, respectively, significantly depressed evoked field potentials in both animal groups. The 5-HT4 agonist RS 67333 (1 microM) was depressant only in sham operated animals. Only after SNL, spinal superfusion with 5-HT1A- or 5-HT1B receptor-antagonists (S)-WAY 100135 (100 microM) or SB 224289 (100 microM), respectively, disinhibited C fibre-evoked potentials, whereas 5-HT2A or 5-HT2B receptor-antagonists 4F 4PP (100 microM) or SB 204741 (100 microM) depressed evoked potentials, suggesting tonic activity of all four subtypes as a consequence of experimental nerve injury. The present findings reveal profound subtype-specific changes in the functional modulatory activities of spinal serotonin receptors following peripheral nerve injury. In particular, spinal hyperexcitation promoted by receptors 5-HT2A and 5-HT2B is suggested as a novel pathogenic pathway contributing to neuropathic pain.
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Affiliation(s)
- Z Aira
- Department of Neurosciences, School of Medicine and Dentistry, Basque Country University, Barrio Sarriena s/n, 48940 Leioa, Spain
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Dogrul A, Ossipov MH, Porreca F. Differential mediation of descending pain facilitation and inhibition by spinal 5HT-3 and 5HT-7 receptors. Brain Res 2009; 1280:52-9. [DOI: 10.1016/j.brainres.2009.05.001] [Citation(s) in RCA: 130] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2009] [Revised: 04/25/2009] [Accepted: 05/04/2009] [Indexed: 01/07/2023]
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Sounvoravong S, Nakashima MN, Wada M, Nakashima K. Modification of antiallodynic and antinociceptive effects of morphine by peripheral and central action of fluoxetine in a neuropathic mice model. ACTA BIOLOGICA HUNGARICA 2007; 58:369-79. [PMID: 18277463 DOI: 10.1556/abiol.58.2007.4.4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously reported that serotonin concentration was reduced in the brain of mice with neuropathic pain and that it may be related to reduction of morphine analgesic effects. To further prove this pharmacological action, we applied fluoxetine, a selective serotonin reuptake inhibitor, to determine whether it suppressed neuropathic pain and examined how its different administration routes would affect antinociceptive and antiallodynic effects of morphine in diabetic (DM) and sciatic nerve ligation (SL) mice, as models of neuropathic pain. Antiallodynia and antinociceptive effect of drugs were measured by using von Frey filament and tail pinch tests, respectively. Fluoxetine given alone, intracerebroventicularly (i.c.v., 15 microg/mouse) or intraperitoneally (i.p., 5 and 10 mg/kg) did not produce any effect in either model. However, fluoxetine given i.p. enhanced both antiallodynic and antinociceptive effects of morphine. Administration of fluoxetine i.c.v., slightly enhanced only the antiallodynic effect of morphine in SL mice. Ketanserine, a serotonin 2A receptor antagonist (i.p., 1 mg/kg) and naloxone, an opioid receptor antagonist (i.p., 3 mg/kg), blocked the combined antinociceptive effect of fluoxetine and morphine. Our data show that fluoxetine itself lacks antinociceptive properties in the two neuropathy models, but it enhances the analgesic effect of morphine in the periphery and suggests that co-administration of morphine with fluoxetine may have therapeutic potential in treatment of neuropathic pain.
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Affiliation(s)
- S Sounvoravong
- Department of Clinical Pharmacy, Division of Analytical Research for Pharmacoinformatics, Graduate School of Biochemical Sciences, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521, Japan
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Berrocoso E, De Benito MD, Mico JA. Role of serotonin 5-HT1A and opioid receptors in the antiallodynic effect of tramadol in the chronic constriction injury model of neuropathic pain in rats. Psychopharmacology (Berl) 2007; 193:97-105. [PMID: 17393145 DOI: 10.1007/s00213-007-0761-8] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Accepted: 02/28/2007] [Indexed: 11/24/2022]
Abstract
RATIONALE Tramadol (1RS, 2RS)-2-[(dimethylamino)-methyl]-1-(3-methoxyphenyl)-cyclohexanol) is an atypical centrally acting analgesic agent with weak opioid receptor affinity that, like some antidepressants, enhances the extraneuronal concentrations of the monoamine neurotransmitters, noradrenaline and serotonin, by interfering with their re-uptake and release mechanisms. OBJECTIVES The present study was undertaken to evaluate the potential role of 5-HT(1A) receptors and opioids receptors in the analgesic effect of tramadol in neuropathic pain. With this aim, the effect of either a selective 5-HT(1A) receptor antagonist (WAY-100635, N-2-[4-(2-methoxyphenyl-1-piperazinyl]ethyl]-N-2-pyridinylcyclohexane carboxamide) or a selective 5-HT(1A) receptor agonist (8-OH-DPAT, 8-hydroxy-2-(di-n-propylamine) tetralin hydrobromide) or an opioid receptor antagonist (naloxone; naloxone hydrochloride dihydrate) was investigated in combination with tramadol by means of the cold-plate test in the chronic constriction injury model in rats. RESULTS The results showed that WAY-100635 (0.8 mg/kg) significantly enhanced the antiallodynic effect of non-effective doses of tramadol (5-10 mg/kg). In contrast, 8-OH-DPAT (0.5 mg/kg) counteracted the antiallodynic effect of an effective dose of tramadol (22 mg/kg). Naloxone (0.5 mg/kg) partially counteracted the antiallodynic effect of tramadol (22 mg/kg). CONCLUSIONS These findings suggest the involvement of opioid and 5-HT(1A) receptors in the antinociceptive effect of tramadol and support the idea that the combination of tramadol with compounds having 5-HT(1A) antagonist properties could be a new strategy to improve tramadol-induced analgesia in neuropathic pain.
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Affiliation(s)
- Esther Berrocoso
- Pharmacology and Neuroscience Research Group, Department of Neuroscience (Pharmacology and Psychiatry), School of Medicine, University of Cádiz, Plaza Falla 9, 11003, Cadiz, Spain,
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Wei H, Pertovaara A. 5-HT1A receptors in endogenous regulation of neuropathic hypersensitivity in the rat. Eur J Pharmacol 2006; 535:157-65. [PMID: 16545367 DOI: 10.1016/j.ejphar.2006.02.019] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Revised: 02/09/2006] [Accepted: 02/13/2006] [Indexed: 11/28/2022]
Abstract
The role of medullary and spinal 5-HT(1A) receptors in endogenous regulation of neuropathic hypersensitivity was studied. When administered in the rostroventromedial medulla or subcutaneously, WAY-100635, a 5-HT(1A) receptor antagonist, attenuated mechanical hypersensitivity in rats with a spinal nerve injury. Thermal or mechanical nociception outside of the injured area was not influenced by medial medullary or subcutaneous administration of WAY-100635. Intrathecal administration of WAY-100635 had no significant effect on pain-related behavior. Suppression of mechanical hypersensitivity induced by medial medullary administration of WAY-100635 was reversed by intrathecal administration of WAY-100635 or atipamezole, an alpha2-adrenoceptor antagonist, but not by naloxone, an opioid receptor antagonist. The results indicate that endogenous release of 5-HT, via action on medial medullary 5-HT(1A) receptors, tonically suppresses descending inhibition in neuropathic animals. Following medial medullary administration of a 5-HT(1A) receptor antagonist, descending pain regulatory pathways are disinhibited. This leads to selective attenuation of neuropathic hypersensitivity, due to action on spinal 5-HT(1A) receptors and alpha2-adrenoceptors.
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Affiliation(s)
- Hong Wei
- Biomedicum Helsinki, Institute of Biomedicine/Physiology, POB 63, 00014 University of Helsinki, Finland
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Wang W, Wu SX, Wang YY, Liu XY, Li YQ. 5-hydroxytryptamine1A receptor is involved in the bee venom induced inflammatory pain. Pain 2004; 106:135-42. [PMID: 14581120 DOI: 10.1016/s0304-3959(03)00315-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Injection of bee venom into one hindpaw of rat can elicit acute inflammation together with spontaneous pain, heat hyperalgesia and mechanical hyperalgesia/allodynia in the injected paw. 5-hydroxytryptamine (5-HT)1A receptor is the predominant receptor subtype in the spinal dorsal horn mediating the function of 5-HT in nociception. The goal of the present study is to assess the role of 5-HT1A receptor in the pain associated with the bee venom induced inflammation. Here we showed that 1 or 4 h after a subcutaneous bee venom challenge, expression of 5-HT1A receptor mRNA in the ipsilateral lumbar spinal cord increased significantly by 80.94 or 37.86%, respectively. Antisense oligodeoxynucleotide knockdown of spinal 5-HT1A receptor attenuated spontaneous pain and reversed heat hyperalgesia in rats injected with bee venom. Thus, the present data suggest a facilitating role for 5-HT1A receptor in bee venom induced inflammatory pain.
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Affiliation(s)
- Wen Wang
- Department of Anatomy and K.K. Leung Brain Research Centre, The Fourth Military Medical University, 17 West Chang'le Road, Xi'an 710032, People's Republic of China
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Scrogin KE. 5-HT1A receptor agonist 8-OH-DPAT acts in the hindbrain to reverse the sympatholytic response to severe hemorrhage. Am J Physiol Regul Integr Comp Physiol 2003; 284:R782-91. [PMID: 12611395 DOI: 10.1152/ajpregu.00478.2002] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Central administration of serotonergic 5-HT1A receptor agonists delays the reflex sympatholytic response to severe hemorrhage in conscious rats. To determine the region where 5-HT1A receptor agonists act to mediate this response, recovery of mean arterial pressure (MAP), heart rate (HR), and renal sympathetic nerve activity (RSNA) was compared in hemorrhaged rats after injection of the selective 5-HT1A agonist, (+)-8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT), in various regions of the cerebroventricular system or the systemic circulation. Three minutes after injection of 8-OH-DPAT (48 nmol/kg), MAP and RSNA were higher in hemorrhaged rats given drug in the fourth ventricle (94 +/- 5 mmHg, 82 +/- 18% of baseline) or the systemic circulation (90 +/- 4 mmHg, 113 +/- 15% of baseline) than in rats given drug in the Aqueduct of Sylvius (63 +/- 4 mmHg, 27 +/- 11% of baseline), the lateral ventricle (42 +/- 3 mmHg, -8 +/- 18% of baseline), or in rats given saline in various brain regions (47 +/- 5 mmHg, -42 +/- 10% of baseline). A lower-dose injection of 8-OH-DPAT (10 nmol/kg) also accelerated the recovery of MAP and RSNA in hemorrhaged rats when given in the fourth ventricle (94 +/- 26 mmHg, 72 +/- 33% of baseline 3 min after injection) but not the systemic circulation (46 +/- 4 mmHg, -25 +/- 30% of baseline). These data indicate that 8-OH-DPAT acts on receptors in the hindbrain to reverse the sympatholytic response to hemorrhage in conscious rats.
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Affiliation(s)
- Karie E Scrogin
- Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Stritch School of Medicine, Maywood, Illinois 60513, USA.
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Zhang YQ, Gao X, Ji GC, Huang YL, Wu GC, Zhao ZQ. Expression of 5-HT1A receptor mRNA in rat lumbar spinal dorsal horn neurons after peripheral inflammation. Pain 2002; 98:287-295. [PMID: 12127030 DOI: 10.1016/s0304-3959(02)00026-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The present study observed the expression of the 5-hydroxytryptamine (5-HT) (1A) receptor mRNA in the lumbar spinal dorsal horn neurons following carrageenan inflammation using in situ hybridization (ISH). We also studied the co-localization of 5-HT(1A) receptor mRNA and gamma-amino butyric acid (GABA) or enkephalin (ENK) immunoreactivities using a combined fluorescent ISH and immunofluorescent histochemical double-staining technique. The finding of this study demonstrated that 5-HT(1A) receptor mRNA was widely distributed in the spinal dorsal horn with the highest density in laminae III-VI. Following carrageenan-induced inflammation, the 5-HT(1A) receptor mRNA expression in all layers of ipsilateral dorsal horn was significantly enhanced, and the peak occurred after 8h. Furthermore, the number of 5-HT(1A) receptor mRNA and GABA or ENK immunoreactive double-labeled cells was also markedly increased 8h after carrageenan injection. These findings suggested that following peripheral inflammation, the synthesis of 5-HT(1A) receptor was increased in the lumbar spinal dorsal horn neurons, especially in spinal GABA and ENK neurons.
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Affiliation(s)
- Yu-Qiu Zhang
- Institute of Neurobiology, Fudan University, 220 Han Dan Road, Shanghai, 200433, People's Republic of China State Key Laboratory of Medical Neurobiology, Fudan University, 138 Yi Xue Yuan Road, Shanghai, 200032, People's Republic of China
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Abstract
Upon receipt in the dorsal horn (DH) of the spinal cord, nociceptive (pain-signalling) information from the viscera, skin and other organs is subject to extensive processing by a diversity of mechanisms, certain of which enhance, and certain of which inhibit, its transfer to higher centres. In this regard, a network of descending pathways projecting from cerebral structures to the DH plays a complex and crucial role. Specific centrifugal pathways either suppress (descending inhibition) or potentiate (descending facilitation) passage of nociceptive messages to the brain. Engagement of descending inhibition by the opioid analgesic, morphine, fulfils an important role in its pain-relieving properties, while induction of analgesia by the adrenergic agonist, clonidine, reflects actions at alpha(2)-adrenoceptors (alpha(2)-ARs) in the DH normally recruited by descending pathways. However, opioids and adrenergic agents exploit but a tiny fraction of the vast panoply of mechanisms now known to be involved in the induction and/or expression of descending controls. For example, no drug interfering with descending facilitation is currently available for clinical use. The present review focuses on: (1) the organisation of descending pathways and their pathophysiological significance; (2) the role of individual transmitters and specific receptor types in the modulation and expression of mechanisms of descending inhibition and facilitation and (3) the advantages and limitations of established and innovative analgesic strategies which act by manipulation of descending controls. Knowledge of descending pathways has increased exponentially in recent years, so this is an opportune moment to survey their operation and therapeutic relevance to the improved management of pain.
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Affiliation(s)
- Mark J Millan
- Department of Psychopharmacology, Institut de Recherches Servier, 125 Chemin de Ronde, 78290 Croissy/Seine, Paris, France.
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Zhang YQ, Gao X, Ji GC, Wu GC. Expression of 5-HT2A receptor mRNA in rat spinal dorsal horn and some nuclei of brainstem after peripheral inflammation. Brain Res 2001; 900:146-51. [PMID: 11325358 DOI: 10.1016/s0006-8993(01)02283-1] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression of 5-hydroxytryptamine 5-HT2A receptor mRNA was studied in the lumbar spinal dorsal horn, nucleus of raphe magnus (NRM), ventrolateral periaqueductal gray (vlPAG) and dorsal raphe nucleus (DRN) following carrageenan inflammation using in situ hybridization technique. The findings of this study demonstrated that 5-HT2A receptor mRNA was expressed with low to moderate levels in lumbar spinal dorsal horn, NRM, vlPAG and DRN. Following carrageenan inflammation, the expression of 5-HT2A receptor mRNA in ipsilateral dorsal horn, bilateral NRM, vlPAG and DRN was significantly increased. The peak occurred at 3 h and then there was a clear decrease but still a substantial number of labeled cells at 24 h after injection of carrageenan. This result suggested that the synthesis of 5-HT2A receptor is enhanced in spinal dorsal horn, NRM, vlPAG and DRN during inflammatory pain.
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Affiliation(s)
- Y Q Zhang
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology, Medical Center of Fudan University, 138 Yi Xue Yuan Road, 200032, Shanghai, People's Republic of China
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Zhang Y, Gao X, Yang ZL, Huang YL, Wu GC. Expression of 5-HT(1A) receptor mRNA in rat nucleus raphe magnus neurons after peripheral inflammation. Brain Res 2000; 887:465-8. [PMID: 11134643 DOI: 10.1016/s0006-8993(00)03037-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The present study demonstrated that 5-HT(1A) receptor mRNA was expressed with moderate level in the NRM neurons. Most of 5-HT(1A) receptor mRNA positive cells were 5-HT neurons, suggesting the majority of 5-HT(1A) receptor in the NRM might be autoreceptors. Eight hours after carrageenan inflammation, the expression of 5-HT(1A) receptor mRNA in the NRM neurons, especially in the 5-HT neurons, was significantly increased. These results suggest that synthesis of 5-HT(1A) receptors, including 5-HT(1A) autoreceptors, is increased in the NRM during peripheral inflammation.
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Affiliation(s)
- Y Zhang
- State Key Laboratory of Medical Neurobiology, Department of Neurobiology, Medical Center of Fudan University, 138 Yi Xue Yuan Road, Shanghai 200032, China
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