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Xu Y, Liu J, He M, Liu R, Belegu V, Dai P, Liu W, Wang W, Xia QJ, Shang FF, Luo CZ, Zhou X, Liu S, McDonald J, Liu J, Zuo YX, Liu F, Wang TH. Mechanisms of PDGF siRNA-mediated inhibition of bone cancer pain in the spinal cord. Sci Rep 2016; 6:27512. [PMID: 27282805 PMCID: PMC4901320 DOI: 10.1038/srep27512] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2014] [Accepted: 05/10/2016] [Indexed: 02/05/2023] Open
Abstract
Patients with tumors that metastasize to bone frequently suffer from debilitating pain, and effective therapies for treating bone cancer are lacking. This study employed a novel strategy in which herpes simplex virus (HSV) carrying a small interfering RNA (siRNA) targeting platelet-derived growth factor (PDGF) was used to alleviate bone cancer pain. HSV carrying PDGF siRNA was established and intrathecally injected into the cavum subarachnoidale of animals suffering from bone cancer pain and animals in the negative group. Sensory function was assessed by measuring thermal and mechanical hyperalgesia. The mechanism by which PDGF regulates pain was also investigated by comparing the differential expression of pPDGFRα/β and phosphorylated ERK and AKT. Thermal and mechanical hyperalgesia developed in the rats with bone cancer pain, and these effects were accompanied by bone destruction in the tibia. Intrathecal injection of PDGF siRNA and morphine reversed thermal and mechanical hyperalgesia in rats with bone cancer pain. In addition, we observed attenuated astrocyte hypertrophy, down-regulated pPDGFRα/β levels, reduced levels of the neurochemical SP, a reduction in CGRP fibers and changes in pERK/ERK and pAKT/AKT ratios. These results demonstrate that PDGF siRNA can effectively treat pain induced by bone cancer by blocking the AKT-ERK signaling pathway.
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Affiliation(s)
- Yang Xu
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Jia Liu
- Institute of Neuroscience, Kunming Medical University, Kunming 650031, PR China
| | - Mu He
- Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Ran Liu
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Visar Belegu
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA, International Center for Spinal Cord Injury, Hugo W. Moser Research Institute at Kennedy Krieger Inc., Baltimore, MD, USA
| | - Ping Dai
- Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Wei Liu
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Wei Wang
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Qing-Jie Xia
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Fei-Fei Shang
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Chao-Zhi Luo
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Xue Zhou
- Department of Histology, Embryology and Neurobiology, West China School of Preclinical and Forensic Medicine, Sichuan University, Chengdu, Sichuan 610041, China
| | - Su Liu
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA, International Center for Spinal Cord Injury, Hugo W. Moser Research Institute at Kennedy Krieger Inc., Baltimore, MD, USA
| | - JohnW. McDonald
- Department of Neurology, Johns Hopkins School of Medicine, Baltimore, MD, USA, International Center for Spinal Cord Injury, Hugo W. Moser Research Institute at Kennedy Krieger Inc., Baltimore, MD, USA
| | - Jin Liu
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Yun-Xia Zuo
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Fei Liu
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
| | - Ting-Hua Wang
- Institute of Neurological Disease, Department of Anesthesiology and Translation Neuroscience Center, West China Hospital, Sichuan University, Chengdu 610041, PR China
- Institute of Neuroscience, Kunming Medical University, Kunming 650031, PR China
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Abstract
In recent years, studies have substantiated the view that P2X3 receptors play a part in the generation and transmission of purinergic signals in inflammatory and chronic neuropathic pain. Data have also been presented to suggest that the process of P2X3 receptor antagonism inhibits inflammatory hyperalgesia, involving the spinal opioid system. The aim of this study was to investigate the effect of the selective P2X3 receptor antagonist A-317491 on the development of antinociceptive tolerance to chronic morphine administration in mice. Daily systemic injection of A-317491 attenuated the morphine-induced antinociceptive tolerance to von Frey and thermal stimuli. Repeated morphine injections alone led to a significant rightward shift in the morphine dose-response curve compared with that with A-317491. A single dose of A-317491 also showed a reversal effect in morphine-tolerant mice. In a withdrawal test, co-administration of A-317491 and morphine also reduced the naloxone-induced withdrawal symptoms compared with the morphine-alone group. Thus, we propose that the P2X3 receptor is involved in the process of morphine antinociceptive tolerance and may be a new therapeutic target in the prevention of tolerance to morphine-induced antinociception.
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Bao Y, Gao Y, Yang L, Kong X, Yu J, Hou W, Hua B. The mechanism of μ-opioid receptor (MOR)-TRPV1 crosstalk in TRPV1 activation involves morphine anti-nociception, tolerance and dependence. Channels (Austin) 2015; 9:235-43. [PMID: 26176938 DOI: 10.1080/19336950.2015.1069450] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Initiated by the activation of various nociceptors, pain is a reaction to specific stimulus modalities. The μ-opioid receptor (MOR) agonists, including morphine, remain the most potent analgesics to treat patients with moderate to severe pain. However, the utility of MOR agonists is limited by the adverse effects associated with the use of these drugs, including analgesic tolerance and physical dependence. A strong connection has been suggested between the expression of the transient receptor potential vanilloid type 1 (TRPV1) ion channel and the development of inflammatory hyperalgesia. TRPV1 is important for thermal nociception induction, and is mainly expressed on sensory neurons. Recent reports suggest that opioid or TRPV1 receptor agonist exposure has contrasting consequences for anti-nociception, tolerance and dependence. Chronic morphine exposure modulates TRPV1 activation and induces the anti-nociception effects of morphine. The regulation of many downstream targets of TRPV1 plays a critical role in this process, including calcitonin gene-related peptide (CGRP) and substance P (SP). Additional factors also include capsaicin treatment blocking the anti-nociception effects of morphine in rats, as well as opioid modulation of TRPV1 responses through the cAMP-dependent PKA pathway and MAPK signaling pathways. Here, we review new insights concerning the mechanism underlying MOR-TRPV1 crosstalk and signaling pathways and discuss the potential mechanisms of morphine-induced anti-nociception, tolerance and dependence associated with the TRPV1 signaling pathway and highlight how understanding these mechanisms might help find therapeutic targets for the treatment of morphine induced antinociception, tolerance and dependence.
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Affiliation(s)
- Yanju Bao
- a Department of Oncology ; Guang'anmen Hospital, China Academy of Chinese Medical Sciences ; Beijing , P. R. China
| | - Yebo Gao
- a Department of Oncology ; Guang'anmen Hospital, China Academy of Chinese Medical Sciences ; Beijing , P. R. China.,b Beijing University of Chinese Medicine ; Beijing , P. R. China
| | - Liping Yang
- c Department of Nephrology ; Guang'anmen Hospital, China Academy of Chinese Medical Sciences ; Beijing , P. R. China
| | - Xiangying Kong
- d Institute of Chinese Materia Medica, China Academy of Chinese Medical Sciences ; Beijing , P. R. China
| | - Jing Yu
- e Department of Oncology ; Beijing Friendship Hospital, Capital Medical University ; Beijing , China
| | - Wei Hou
- a Department of Oncology ; Guang'anmen Hospital, China Academy of Chinese Medical Sciences ; Beijing , P. R. China
| | - Baojin Hua
- a Department of Oncology ; Guang'anmen Hospital, China Academy of Chinese Medical Sciences ; Beijing , P. R. China
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Nguyen TL, Nam YS, Lee SY, Kim HC, Jang CG. Effects of capsazepine, a transient receptor potential vanilloid type 1 antagonist, on morphine-induced antinociception, tolerance, and dependence in mice. Br J Anaesth 2010; 105:668-74. [PMID: 20719804 DOI: 10.1093/bja/aeq212] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Repeated morphine treatment has been shown to induce transient receptor potential vanilloid type 1 (TRPV1) expression in the spinal cord, dorsal root ganglion (DRG), and sciatic nerve of a rat model. Increased TRPV1 expression may therefore play a role in morphine tolerance. In this study, we evaluated the hypothesis that blockage of TRPV1 may be useful as an adjunctive pain management therapy. We investigated whether blockage of TRPV1 by capsazepine, a TRPV1 antagonist, affected antinociception, development of tolerance, and physical dependence on morphine in mice. METHODS Institute of Cancer Research mice were pretreated with capsazepine and post-treated with morphine acutely and repeatedly. Antinociception and its tolerance were assessed using the hot-plate test. Morphine dependence was examined through the manifestation of withdrawal symptoms induced by naloxone in morphine-dependent mice. RESULTS Acute capsazepine treatment (5 mg kg⁻¹, i.p.) potentiated the antinociceptive effects of morphine, as measured by the hot-plate test. Repeated co-treatment of capsazepine (2.5 mg kg⁻¹ i.p.) with morphine attenuated the development of tolerance to the antinociceptive effect of morphine. The development of morphine dependence was also reduced by capsazepine (1.25 or 2.5 mg kg⁻¹ i.p.). CONCLUSIONS Our results suggest that TRPV1 antagonists can be used adjunctively to morphine treatment because they strengthen morphine antinociception and prevent the development of tolerance, and also physical dependence, on morphine.
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Affiliation(s)
- T-L Nguyen
- Department of Pharmacology, School of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea
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Trang T, Quirion R, Jhamandas K. The spinal basis of opioid tolerance and physical dependence: Involvement of calcitonin gene-related peptide, substance P, and arachidonic acid-derived metabolites. Peptides 2005; 26:1346-55. [PMID: 16042975 DOI: 10.1016/j.peptides.2005.03.031] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Chronic opioid use in the management of pain is limited by development of analgesic tolerance and physical dependence. The mechanisms underlying tolerance-dependence are not entirely clear, however, recent evidence suggests that spinal adaptations leading to increased activity of sensory neuropeptides (calcitonin gene-related peptide (CGRP), substance P) and their downstream signaling messengers derived from metabolism of arachidonic acid: prostaglandins (PG), lipoxygenase (LOX) metabolites, and endocannabinoids, plays an important role in this phenomenon. In this communication we review the evidence implicating these factors in the induction and expression of opioid tolerance and physical dependence at the spinal level.
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Affiliation(s)
- Tuan Trang
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, Kingston, Ont., Canada K7L 3N6
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Zhou X, Li JJ, Yu LC. Plastic changes of calcitonin gene-related peptide in morphine tolerance: Behavioral and immunohistochemical study in rats. J Neurosci Res 2003; 74:622-9. [PMID: 14598307 DOI: 10.1002/jnr.10770] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The present study was undertaken to investigate the plasticity of calcitonin gene-related peptide (CGRP) in antinociception after morphine tolerance in rats. The hindpaw withdrawal latencies (HWLs) to both thermal and mechanical stimulation increased significantly after intracerebroventricular injection of 2.5 nmol of CGRP in opioid-naive rats, indicating that CGRP produces an antinociceptive effect in the brain. Furthermore, there was an antinociceptive effect after intracerebroventricular injection of 2.5 nmol of CGRP in morphine-tolerant rats. Interestingly, the antinociceptive effect induced by intracerebroventricular injection of CGRP was lower in morphine-tolerant rats than that in opioid-naive rats at the same dose. At the same time, there was downregulation of CGRP-like immunoreactivity in both lateral septal nucleus and central nucleus of amygdala tested by immunohistochemical methods, whereas no significant changes were observed in arcuate nucleus of hypothalamus and periaqueductal gray after morphine treatment in rats. The present study demonstrates plastic changes in both CGRP-induced antinociception and CGRP-like immunoreactivity in rat brain after morphine tolerance, suggesting that CGRP may play an important role in morphine tolerance.
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Affiliation(s)
- Xiang Zhou
- College of Life Sciences, Center for Brain and Cognitive Science and National Laboratory of Biomembrane and Membrane Biotechnology, Peking University, Beijing, People's Republic of China
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Trang T, Sutak M, Quirion R, Jhamandas K. Spinal administration of lipoxygenase inhibitors suppresses behavioural and neurochemical manifestations of naloxone-precipitated opioid withdrawal. Br J Pharmacol 2003; 140:295-304. [PMID: 12970109 PMCID: PMC1574036 DOI: 10.1038/sj.bjp.0705440] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. This study investigated the role of spinal lipoxygenase (LOX) products in the induction and expression of opioid physical dependence using behavioural assessment of withdrawal and immunostaining for CGRP and Fos protein expression in the spinal cord. 2. Administration of escalating doses (5-50 mg kg-1; i.p.) of morphine for 5 days markedly elevated CGRP-like immunoreactivity in the dorsal horn of the rat spinal cord. Naloxone (2 mg kg-1; i.p.) challenge precipitated a robust withdrawal syndrome that depleted CGRP-like immunoreactivity and increased the number of Fos-like immunoreactive neurons in the dorsal horn. 3. Intrathecal administration of NDGA (10, 20 microg), a nonselective LOX inhibitor, AA-861 (1.5, 3 microg), a 5-LOX selective inhibitor, or baicalein (1.4, 2.8 microg), a 12-LOX selective inhibitor, concurrently with systemic morphine for 5 days or as a single injection immediately preceding naloxone challenge, blocked the depletion of CGRP-like immunoreactivity, prevented increase in the number of Fos-like immunoreactive neurons in the dorsal horn, and significantly attenuated the morphine withdrawal syndrome. 4. The results of this study suggest that activity of LOX products, at the spinal level, contributes to the expression of opioid physical dependence, and that this activity may be expressed through increased sensory neuropeptide release.
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Affiliation(s)
- Tuan Trang
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, 523 Botterell Hall, Kingston, Ont., Canada K7L 3N6
| | - Maaja Sutak
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, 523 Botterell Hall, Kingston, Ont., Canada K7L 3N6
| | - Remi Quirion
- Douglas Hospital Research Centre and Department of Psychiatry, McGill University, Montreal, Que., Canada H9 H 1R3
| | - Khem Jhamandas
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, 523 Botterell Hall, Kingston, Ont., Canada K7L 3N6
- Author for correspondence:
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Trang T, Sutak M, Quirion R, Jhamandas K. The role of spinal neuropeptides and prostaglandins in opioid physical dependence. Br J Pharmacol 2002; 136:37-48. [PMID: 11976266 PMCID: PMC1762111 DOI: 10.1038/sj.bjp.0704681] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study examined the role of spinal calcitonin gene-related peptide (CGRP), substance P, and prostaglandins in the development and expression of opioid physical dependence. Administration of escalating doses (5 - 100 mg kg-1, i.p.) of morphine for 7 days markedly elevated CGRP and substance P- immunoreactivity in the dorsal horn of the rat spinal cord. Naloxone (2 mg kg-1, i.p.) challenge decreased both CGRP and substance P immunoreactivity and precipitated a robust withdrawal syndrome. Acute intrathecal pre-treatment with a CGRP receptor antagonist, CGRP(8 - 37) (4, 8 microg), a substance P receptor antagonist, SR 140333 (1.4, 2.8 microg), a cyclo-oxygenase (COX) inhibitor, ketorolac (30, 45 microg), and COX-2 selective inhibitors, DuP 697 (10, 30 microg) and nimesulide (30 microg), 30 min before naloxone challenge, partially attenuated the symptoms of morphine withdrawal. CGRP(8 - 37) (8 microg), but no other agents, inhibited the decrease in CGRP immunoreactivity. Chronic intrathecal treatment with CGRP(8 - 37) (4, 8 microg), SR 140333 (1.4 microg), ketorolac (15, 30 microg), DuP 697 (10, 30micro g), and nimesulide (30 microg), delivered with daily morphine injection significantly attenuated both the symptoms of withdrawal and the decrease in CGRP but not substance P immunoreactivity. The results of this study suggest that activation of CGRP and substance P receptors, at the spinal level, contributes to the induction and expression of opioid physical dependence and that this activity may be partially expressed through the intermediary actions of prostaglandins.
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Affiliation(s)
- Tuan Trang
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | - Maaja Sutak
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, Kingston, Ontario, Canada, K7L 3N6
| | - Remi Quirion
- Douglas Hospital Research Centre and Department of Psychiatry, McGill University, Montreal, Quebec, Canada, H9H 1R3
| | - Khem Jhamandas
- Department of Pharmacology and Toxicology, Faculty of Health Sciences, Queen's University, Kingston, Ontario, Canada, K7L 3N6
- Author for correspondence:
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Lafond J, St-Pierre S, Masse A, Savard R, Simoneau L. Calcitonin gene-related peptide receptor in human placental syncytiotrophoblast brush-border and basal plasma membranes. Placenta 1997; 18:181-8. [PMID: 9089780 DOI: 10.1016/s0143-4004(97)90091-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Minerals, such as calcium and potassium, are essential for fetal development, but their transplacental transport, and in particular, the effect of hormones on this process has not been extensively studied. Human alpha-calcitonin gene-related peptide (h alpha CGRP), a hormone constituted of 37 amino acids, is obtained by the alternative splicing of the mRNA from the calcitonin gene, and could be implicated in placental ion transport. In order to study the presence of this receptor, brush-border and basal plasma membranes were purified, and membrane binding studies were conducted using [125I]h alpha CGRP. The initiation of binding of [125I]h alpha CGRP to both membranes was rapid and reached maximal value after 10 min of incubation at 37 degrees C. Scratchard analysis revealed single-affinity binding sites for h alpha CGRP with Kd equal to 4412.45 +/- 604.81 pM and 2673.24 +/- 552.51 pM for brush-border and basal plasma membranes, respectively, which were significantly different. Moreover, the maximal number of receptors was significantly different (P < 0.001) in both membranes, with Bmax of 627.94 +/- 31.40 fmol/mg protein for brush-border membranes and 343.70 +/- 43.52 fmol/mg protein in basal-plasma membranes. Competitive displacement of [125I]h alpha CGRP with other ligands showed the following potencies; h alpha CGRP approximately h beta CGRP approximately Cys (acm)2,7 CGRP > CGRP (8-37), but no competition was observed with human and salmon calcitonin. Half-maximal displacement for human alpha- and beta CGRP was reached at approximately 10(-10)M for brush-border and basal-plasma membranes. alpha- and beta CGRP, and their fragment and analogue, stimulated cyclic AMP production in placental homogenate ranging from 143-163 per cent. Thus, our results show the presence of CGRP-specific receptors in both the syncytiotrophoblast membranes of human placenta. The role(s) of this related peptide in placenta remains to be investigated.
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Affiliation(s)
- J Lafond
- Department of Biological Sciences, University of Quebec in Montreal
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Azarov AV, Szabó G, Czakó L, Telegdy G. Effects of calcitonin gene-related peptide on acute and chronic effects of morphine. Pharmacol Biochem Behav 1995; 52:595-9. [PMID: 8545480 DOI: 10.1016/0091-3057(95)00146-n] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Calcitonin gene-related peptide (CGRP), which has been observed in different parts of the nervous system, is known to modify pain sensitivity to different stimuli in rats and mice. The aim of this study was to investigate the possible interaction of CGRP with morphine on nociception in adult male NMRI mice after central administration of the peptide. CGRP (20 or 200 ng) did not itself modify pain sensitivity in the tail-flick test and did not affect the acute antinociceptive action of a single dose of morphine in the same test. However, CGRP suppressed the development of rapid tolerance to morphine in a dose-dependent manner, but had no action on the development of chronic tolerance to morphine and on manifestations of naloxone-precipitated withdrawal syndrome.
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Affiliation(s)
- A V Azarov
- Department of Pathophysiology, Albert Szent-Györgyi Medical University, Szeged, Hungary
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11
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Ménard DP, van Rossum D, Kar S, Quirion R. Alteration of calcitonin gene related peptide and its receptor binding sites during the development of tolerance to mu and delta opioids. Can J Physiol Pharmacol 1995; 73:1089-95. [PMID: 8846407 DOI: 10.1139/y95-156] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Calcitonin gene related peptide (CGRP), one of the most abundant peptides in the spinal cord, is localized in primary afferents and released following nociceptive stimuli. Its colocalization and corelease with substance P, a well-known nociceptive neuropeptide, support the importance of CGRP in pain mechanisms. However, its distinctive function in that regard remains to be fully established. Recently, we reported that increases in CGRP-like immunostaining and decrements in specific 125I-labelled human CGRP alpha ([125I]hCGRP alpha) binding sites in the spinal cord were correlated with the development of tolerance to the spinal antinociceptive action of a mu opioid agonist, morphine. The goal of the present study was to investigate whether the development of tolerance to other classes of opioids, namely, delta and kappa agonists, can also alter CGRP-like immunostaining and receptors in the rat spinal cord. The antinociceptive effects of all opioids were monitored by the tail-immersion test. Tolerance to their antinociceptive properties was induced by the infusion for 7 days of mu (morphine sulfate, 7.5 micrograms/h), delta D([D-Pen2,D-Pen5]enkephalin (DPDPE), 2.0 micrograms/h), and kappa (U-50488H, 10.0 micrograms/h) related agonists at the spinal level (L4), using osmotic minipumps. We confirmed that rats chronically treated with morphine showed significant decreases in [125I]CGRP alpha binding in laminae I, II, and III of the L4 spinal cord, while CGRP-like immunostaining was increased in these same laminae. Similar effects were observed following a treatment with the delta agonist, DPDPE, while the kappa agonist, U-50488H, apparently only slightly decreased [125I]CGRP alpha] binding in lamina II. Binding in other laminae and CGRP-like immunostaining were not affected. These results suggest a specific interaction between spinal CGRP systems and the development of tolerance to the spinal antinociceptive effects of mu- and delta-related agonists.
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MESH Headings
- 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer
- Animals
- Autoradiography
- Calcitonin Gene-Related Peptide/analysis
- Drug Tolerance
- Enkephalin, D-Penicillamine (2,5)-
- Enkephalins/pharmacology
- Immunohistochemistry
- Male
- Morphine/pharmacology
- Narcotics/pharmacology
- Pyrrolidines/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptors, Calcitonin Gene-Related Peptide/analysis
- Receptors, Opioid, delta/agonists
- Receptors, Opioid, mu/agonists
- Spinal Cord/chemistry
- Spinal Cord/drug effects
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Affiliation(s)
- D P Ménard
- Douglas Hospital Research Centre, McGill University, Verdun, QC, Canada
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