1
|
Shubayev VI, Strongin AY, Yaksh TL. Structural homology of myelin basic protein and muscarinic acetylcholine receptor: Significance in the pathogenesis of complex regional pain syndrome. Mol Pain 2018; 14:1744806918815005. [PMID: 30392459 PMCID: PMC6287297 DOI: 10.1177/1744806918815005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Complex regional pain syndrome is an extremely painful condition that develops after trauma to a limb. Complex regional pain syndrome exhibits autoimmune features in part mediated by autoantibodies against muscarinic‐2 acetylcholine (M2) receptor. The mechanisms underlying the M2 receptor involvement in complex regional pain syndrome remain obscure. Based on our recent work demonstrating that limb nerve trauma releases a potent proalgesic, immunodominant myelin basic protein fragment, our present sequence database analyses reveal an unexpected and previously undescribed structural homology of the proalgesic myelin basic protein fragment with the M2 receptor. As both complex regional pain syndrome and the proalgesic myelin basic protein activity are prevalent in females, this myelin basic protein/M2 homology presents an inviting hypothesis explaining the mechanisms of autoimmune pathogenesis and sexual dimorphism that underlies vulnerability toward developing complex regional pain syndrome and other pain states with neuropathic features. This hypothesis may aid in the development of novel diagnostic and therapeutic strategies to chronic pain.
Collapse
Affiliation(s)
- Veronica I Shubayev
- 1 Department of Anesthesiology, University of California, San Diego, La Jolla, CA, USA.,2 VA San Diego Healthcare System, La Jolla, CA, USA
| | - Alex Y Strongin
- 3 Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA, USA
| | - Tony L Yaksh
- 1 Department of Anesthesiology, University of California, San Diego, La Jolla, CA, USA
| |
Collapse
|
2
|
Brown DA. Regulation of neural ion channels by muscarinic receptors. Neuropharmacology 2017; 136:383-400. [PMID: 29154951 DOI: 10.1016/j.neuropharm.2017.11.024] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2016] [Revised: 10/26/2017] [Accepted: 11/13/2017] [Indexed: 12/20/2022]
Abstract
The excitable behaviour of neurons is determined by the activity of their endogenous membrane ion channels. Since muscarinic receptors are not themselves ion channels, the acute effects of muscarinic receptor stimulation on neuronal function are governed by the effects of the receptors on these endogenous neuronal ion channels. This review considers some principles and factors determining the interaction between subtypes and classes of muscarinic receptors with neuronal ion channels, and summarizes the effects of muscarinic receptor stimulation on a number of different channels, the mechanisms of receptor - channel transduction and their direct consequences for neuronal activity. Ion channels considered include potassium channels (voltage-gated, inward rectifier and calcium activated), voltage-gated calcium channels, cation channels and chloride channels. This article is part of the Special Issue entitled 'Neuropharmacology on Muscarinic Receptors'.
Collapse
Affiliation(s)
- David A Brown
- Department of Neuroscience, Physiology & Pharmacology, University College London, Gower Street, London, WC1E 6BT, UK.
| |
Collapse
|
3
|
De Angelis F, Marinelli S, Fioretti B, Catacuzzeno L, Franciolini F, Pavone F, Tata AM. M2 receptors exert analgesic action on DRG sensory neurons by negatively modulating VR1 activity. J Cell Physiol 2014; 229:783-90. [PMID: 24166293 DOI: 10.1002/jcp.24499] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2013] [Accepted: 10/18/2013] [Indexed: 11/08/2022]
Abstract
The peripheral application of the M2 cholinergic agonist arecaidine on sensory nerve endings shows anti-nociceptive properties. In this work, we analyze in vitro, the mechanisms downstream M2 receptor activation causing the analgesic effects, and in vivo the effects produced by M2 agonist arecaidine administration on nociceptive responses in a murine model of nerve growth factor (NGF)-induced pain. Cultured DRG neurons treated with arecaidine showed a decreased level of VR1 and SP transcripts. Conversely, we found an increased expression of VR1 and SP transcripts in DRG from M2/M4(-/-) mice compared to WT and M1(-/-) mice, confirming the inhibitory effect in particular of M2 receptors on SP and VR1 expression. Patch-clamp experiments in the whole-cell configuration showed that arecaidine treatment caused a reduction of the fraction of capsaicin-responsive cells, without altering the mean capsaicin-activated current in responsive cells. We also demonstrated that arecaidine prevents PKCϵ translocation to the plasma membrane after inflammatory agent stimulation, mainly in medium-small sensory neurons. Finally, in mice, we have observed that intraperitoneal injection of arecaidine reduces VR1 expression blocking hyperalgesia and allodynia caused by NGF intraplantar administration. In conclusion, our data demonstrate that in vivo M2 receptor activation induces desensitization to mechanical and heat stimuli by a down-regulation of VR1 expression and by the inhibition of PKCϵ activity hindering its translocation to the plasma membrane, as suggested by in vitro experiments.
Collapse
Affiliation(s)
- Federica De Angelis
- Department of Biology and Biotechnologies C. Darwin, "Sapienza" University of Rome, Rome, Italy
| | | | | | | | | | | | | |
Collapse
|
4
|
Jositsch G, Papadakis T, Haberberger RV, Wolff M, Wess J, Kummer W. Suitability of muscarinic acetylcholine receptor antibodies for immunohistochemistry evaluated on tissue sections of receptor gene-deficient mice. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 2009; 379:389-95. [PMID: 18974978 PMCID: PMC3896859 DOI: 10.1007/s00210-008-0365-9] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2008] [Accepted: 10/08/2008] [Indexed: 01/16/2023]
Abstract
Acetylcholine (ACh) is a major regulator of visceral function exerting pharmacologically relevant effects upon smooth muscle tone and epithelial function via five types of muscarinic receptors (M1R-M5R). In this paper, we assessed the specificity of muscarinic receptor (MR) antibodies in immunohistochemical labelling on tissue sections by analysing specimens from wild-type and respective gene-deficient mice. Of 24 antibodies evaluated in this study, 16 were tested at 18 different conditions each, and eight of them in 21 different protocols, resulting in a total number of 456 antibody/protocol combinations. Each of them was tested at four antibody dilutions at minimum, so that finally, at least 1,824 conditions were evaluated. For each of them, dorsal root ganglia, urinary bladder and cross-sections through all thoracic viscera were investigated. In all cases where the antigen was available, at least one incubation condition was identified in which only select cell types were immunolabelled in the positive control but remained unlabelled in the pre-absorption control. With two exceptions (M2R antibodies), however, all antibodies produced identical immunohistochemical labelling patterns in tissues taken from corresponding gene-deficient mice even when the pre-absorption control in wild-type mice suggested specificity. Hence, the present data demonstrate the unpleasant fact that reliable immunohistochemical localisation of MR subtypes with antibodies is the exception rather than the rule. Immunohistochemical detection of MR subtype localisation in tissue sections of peripheral organs is limited to the M2R subtype utilising the most commonly used methodological approaches.
Collapse
MESH Headings
- Animal Structures/chemistry
- Animals
- Antibodies/immunology
- Antibodies, Monoclonal/immunology
- Antibody Specificity/immunology
- Immunohistochemistry/methods
- Mice
- Mice, Inbred Strains
- Mice, Knockout
- Receptor, Muscarinic M1/analysis
- Receptor, Muscarinic M1/genetics
- Receptor, Muscarinic M1/immunology
- Receptor, Muscarinic M2/analysis
- Receptor, Muscarinic M2/genetics
- Receptor, Muscarinic M2/immunology
- Receptor, Muscarinic M3/analysis
- Receptor, Muscarinic M3/genetics
- Receptor, Muscarinic M3/immunology
- Receptor, Muscarinic M4/analysis
- Receptor, Muscarinic M4/genetics
- Receptor, Muscarinic M4/immunology
- Receptor, Muscarinic M5/analysis
- Receptor, Muscarinic M5/genetics
- Receptor, Muscarinic M5/immunology
- Receptors, Muscarinic/analysis
- Receptors, Muscarinic/genetics
- Receptors, Muscarinic/immunology
Collapse
Affiliation(s)
- Gitte Jositsch
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, D-35385 Giessen, Germany
| | - Tamara Papadakis
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, D-35385 Giessen, Germany
| | - Rainer V. Haberberger
- Department of Anatomy & Histology, Flinders University of South Australia, Adelaide, Australia
| | - Miriam Wolff
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, D-35385 Giessen, Germany
| | - Jürgen Wess
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, Maryland, USA
| | - Wolfgang Kummer
- Institute of Anatomy and Cell Biology, Justus-Liebig-University Giessen, Aulweg 123, D-35385 Giessen, Germany
| |
Collapse
|
5
|
Hayashida KI, Bynum T, Vincler M, Eisenach JC. Inhibitory M2 muscarinic receptors are upregulated in both axotomized and intact small diameter dorsal root ganglion cells after peripheral nerve injury. Neuroscience 2006; 140:259-68. [PMID: 16580144 DOI: 10.1016/j.neuroscience.2006.02.013] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2005] [Revised: 01/31/2006] [Accepted: 02/01/2006] [Indexed: 11/24/2022]
Abstract
Acetylcholine reduces nociceptive input in part by activating inhibitory M2 muscarinic receptors on primary sensory neurons, and acetylcholinesterase inhibitors and muscarinic agonists produce analgesia in humans and animals. M2 muscarinic receptors are upregulated in animals with diabetic neuropathy, but their level of expression and function after peripheral nerve injury has not been previously examined. This study tested, using intracellular Ca(2+) response to membrane depolarization, the effect of the M2 muscarinic receptor agonist bethanechol on individual dorsal root ganglion cells from normal and L5-6 spinal nerve-ligated rats, followed by M2 muscarinic receptor immunostaining. We also examined functional transient receptor potential for vanilloids-1 activity by determining intracellular Ca(2+) response evoked by capsaicin in M2 muscarinic receptor immunoreactive cells. In normal dorsal root ganglion cells, bethanechol inhibited the Ca(2+) response in a concentration-related fashion, and this inhibition was blocked by the M2 muscarinic receptor antagonist gallamine. Cells expressing M2 muscarinic receptors by immunostaining were significantly inhibited by bethanechol, whereas those lacking positive staining were not. The proportion of studied dorsal root ganglion neurons with positive M2 muscarinic receptor staining increased significantly in the injured ipsilateral L5-6 and the uninjured ipsilateral L4 ganglia, but not in the contralateral dorsal root ganglion neurons compared with normals. In contrast, the proportion of neurons responding to capsaicin significantly decreased in the injured ipsilateral L5-6 dorsal root ganglion cells. These results suggest that inhibitory M2 muscarinic receptors are upregulated in small- and medium-sized axotomized dorsal root ganglion neurons and their uninjured neighbors following nerve injury, and may represent an appropriate target for analgesia in this setting.
Collapse
Affiliation(s)
- K-I Hayashida
- Department of Anesthesiology and Center for the Pharmacologic Plasticity in the Presence of Pain, Wake Forest University School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157, USA
| | | | | | | |
Collapse
|
6
|
Dussor GO, Helesic G, Hargreaves KM, Flores CM. Cholinergic modulation of nociceptive responses in vivo and neuropeptide release in vitro at the level of the primary sensory neuron. Pain 2004; 107:22-32. [PMID: 14715385 DOI: 10.1016/j.pain.2003.09.022] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Muscarinic acetylcholine receptors (mAChRs) have been widely reported as pharmacological targets for the treatment of pain. However, most of these efforts have focused on CNS mAChRs and their role in modulating nociception at the level of the spinal cord. The present study examines the contribution of peripheral mAChRs in trigeminal nociceptive pathways using a combination of in vivo and in vitro approaches. In the formalin model of orofacial nociception in rats, a peri-oral co-injection of the M2 agonist arecaidine dose-dependently inhibited phase 2 nocifensive behavior up to approximately 50% at 5 nmol. This effect was blocked by co-treatment with the mAChR antagonist atropine and was not seen when arecaidine was administered under the skin of the back, a site distant from that of the formalin injection. In vitro superfusion of isolated rat buccal mucosa with the non-selective mAChR agonist muscarine or arecaidine led to a concentration-dependent inhibition of capsaicin-evoked CGRP release to 39% (EC50=255 nM) and 28% (EC50=847 nM) of control values, respectively. Both responses were blocked by the non-selective mAChR antagonist atropine or the M2 antagonist gallamine. Further, the endogenous ligand ACh produced a bi-phasic response, potentiating evoked CGRP release to 195% of control (EC50= 918nM) and inhibiting evoked CGRP release to 45% of control (EC50=255 microM), effects that were shown to be mediated by nAChRs and mAChRs, respectively. Finally, combined in situ hybridization/immunofluorescence demonstrated that m2 mRNA was present in 20% of trigeminal ganglion neurons between 30 and 60 microm in diameter and that 5-9% of these also expressed CGRP or VR1 immunoreactivity. These results show that activation of peripheral M2 receptors produces antinociception in vivo and the inhibition of nociceptor activity in vitro. While histological analyses at the level of the trigeminal neuronal cell bodies leave open the question of whether the effects of M2 agonists are direct or indirect, these data indicate that primary sensory neuronal M2 receptors may represent a viable peripheral target for the treatment of pain and inflammation.
Collapse
MESH Headings
- Acetylcholine/metabolism
- Acetylcholine/pharmacology
- Analysis of Variance
- Animals
- Arecoline/analogs & derivatives
- Arecoline/pharmacology
- Atropine/pharmacology
- Behavior, Animal/drug effects
- Bungarotoxins/pharmacology
- Calcitonin Gene-Related Peptide/metabolism
- Capsaicin/pharmacology
- Cell Count
- Disinfectants/pharmacology
- Dose-Response Relationship, Drug
- Drug Combinations
- Drug Interactions
- Formaldehyde/pharmacology
- Gallamine Triethiodide/pharmacology
- Gene Expression Regulation/drug effects
- Grooming/drug effects
- In Situ Hybridization
- In Vitro Techniques
- Male
- Mecamylamine/pharmacology
- Mouth Mucosa/drug effects
- Muscarinic Antagonists/pharmacology
- Neurons, Afferent/drug effects
- Neurons, Afferent/physiology
- Nicotinic Antagonists/pharmacology
- Pain/metabolism
- Pain Measurement/drug effects
- RNA, Messenger/metabolism
- Radioimmunoassay
- Rats
- Rats, Sprague-Dawley
- Receptor, Muscarinic M2/genetics
- Receptor, Muscarinic M2/metabolism
- Receptors, Drug/genetics
- Receptors, Drug/metabolism
- Time
- Trigeminal Ganglion/cytology
- Trigeminal Ganglion/drug effects
- Trigeminal Ganglion/metabolism
Collapse
Affiliation(s)
- Gregory O Dussor
- Department of Pharmacology, The University of Texas Health Science Center, San Antonio, TX 78229, USA
| | | | | | | |
Collapse
|
7
|
Stewart W, Maxwell DJ. Distribution of and organisation of dorsal horn neuronal cell bodies that possess the muscarinic m2 acetylcholine receptor. Neuroscience 2003; 119:121-35. [PMID: 12763074 DOI: 10.1016/s0306-4522(03)00116-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cholinergic systems in the dorsal horn are involved in antinociception but little is known about the organisation of receptors that mediate this process. In this study we examined immunocytochemical properties of dorsal horn neuronal cell bodies that express the m2 muscarinic acetylcholine receptor. Tissue was examined with confocal laser scanning microscopy and quantitative analysis performed. Immunoreactive cells were found throughout the dorsal horn and in lamina X. Quantitative analysis revealed that 22% of neuronal somata in the dorsal horn possess the receptor. The greatest concentration of cells was found in deeper laminae (IV-VI) and around lamina X. A proportion of cholinergic cells (labelled with an antibody against choline acetyltransferase) were immunoreactive for the receptor (approximately, 40% of dorsal horn cells and 44% of lamina X cells). Populations of presumed inhibitory interneurons also displayed immunoreactivity for the receptor. Between 27-34% of cells immunoreactive for GABA, nitric oxide synthase and the somatostatin receptor(2A) expressed the receptor but only 8% of parvalbumin-immunoreactive cells displayed receptor immunoreactivity. Cells labelled with neurotensin, which belong to a subgroup of excitatory neurons, displayed no receptor immunoreactivity. A small number neurokinin-1 receptor-immunoreactive cells in lamina I possessed m2 immunoreactivity but 42% of laminae III/IV neurokinin-1 cells possessed it. This study shows that a significant proportion of cell bodies in the dorsal horn express the muscarinic m2 acetylcholine receptor. The receptor is present on some cholinergic neurons and therefore may function as an autoreceptor. It is associated with inhibitory local circuit neurons and may have a role in the modulation of specific inhibitory systems. It is also found on a proportion of projection cells that possess the neurokinin-1 receptor. This could be the basis of some of the antinociceptive actions of acetylcholine.
Collapse
Affiliation(s)
- W Stewart
- Spinal Cord Group, Institute of Biomedical and Life Sciences, West Medical Building, University of Glasgow, Glasgow G12 8QQ, UK
| | | |
Collapse
|
8
|
Pannese E. Perikaryal surface specializations of neurons in sensory ganglia. INTERNATIONAL REVIEW OF CYTOLOGY 2003; 220:1-34. [PMID: 12224547 DOI: 10.1016/s0074-7696(02)20002-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Slender projections, similar to microvilli, are the main specialization of the perikaryal surface of sensory ganglion neurons. The extent of these projections correlates closely with the volume of the corresponding nerve cell body. It is likely that the role of perikaryal projections of sensory ganglion neurons, which lack dendrites, is to maintain the surface-to-volume ratio of the nerve cell body above some critical level for adequate metabolic exchange. Satellite cells probably have the ability to promote, or provide a permissive environment for, the outgrowth of these projections. It is not yet known whether the effect of satellite cells is mediated by molecules associated with their plasma membrane or by diffusible factors. Furthermore, receptor molecules for numerous chemical agonists are located on the nerve cell body surface, but it is not known whether certain molecules are located exclusively on perikaryal projections or are also present on the smooth surface between these projections. Further study of the nerve cell body surface and of the influence that satellite cells exert on it will improve our understanding of the interactions between sensory ganglion neurons and satellite neuroglial cells.
Collapse
Affiliation(s)
- Ennio Pannese
- Institute of Histology, Embryology, and Neurocytology, University of Milan, Italy
| |
Collapse
|
9
|
Lips KS, Pfeil U, Kummer W. Coexpression of alpha 9 and alpha 10 nicotinic acetylcholine receptors in rat dorsal root ganglion neurons. Neuroscience 2003; 115:1-5. [PMID: 12401316 DOI: 10.1016/s0306-4522(02)00274-9] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Previous binding studies have suggested the presence of a so far unknown nicotinic acetylcholine receptor subunit in dorsal root ganglia (Pugh et al., 1995). Here, we investigated whether the most recently identified subunit, alpha10, and its potential interaction partner, alpha9 (Elgoyhen et al., 2001), are expressed in these ganglia. All neurons of rat dorsal root ganglia, but no glial cells, expressed both alpha9 and alpha10 mRNA in in situ hybridization, and exhibited alpha10 immunoreactivity using a newly raised antibody. These findings were confirmed by RT-PCR and western blotting. The data show that dorsal root ganglion neurons coexpress alpha9 and alpha10 nicotinic receptor subunits, thereby providing the first example of neuronal expression of this receptor subunit pair.
Collapse
Affiliation(s)
- K S Lips
- Institute for Anatomy and Cell Biology, Justus-Liebig-University, Aulweg 123, D-35385 Giessen, Germany
| | | | | |
Collapse
|
10
|
Duttaroy A, Gomeza J, Gan JW, Siddiqui N, Basile AS, Harman WD, Smith PL, Felder CC, Levey AI, Wess J. Evaluation of muscarinic agonist-induced analgesia in muscarinic acetylcholine receptor knockout mice. Mol Pharmacol 2002; 62:1084-93. [PMID: 12391271 DOI: 10.1124/mol.62.5.1084] [Citation(s) in RCA: 118] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Centrally active muscarinic agonists display pronounced analgesic effects. Identification of the specific muscarinic acetylcholine receptor (mAChR) subtype(s) mediating this activity is of considerable therapeutic interest. To examine the roles of the M(2) and M(4) receptor subtypes, the two G(i)/G(o)-coupled mAChRs, in mediating agonist-dependent antinociception, we generated a mutant mouse line deficient in both M(2) and M(4) mAChRs [M(2)/M(4) double-knockout (KO) mice]. In wild-type mice, systemic, intrathecal, or intracerebroventricular administration of centrally active muscarinic agonists resulted in robust analgesic effects, indicating that muscarinic analgesia can be mediated by both spinal and supraspinal mechanisms. Strikingly, muscarinic agonist-induced antinociception was totally abolished in M(2)/M(4) double-KO mice, independent of the route of application. The nonselective muscarinic agonist oxotremorine showed reduced analgesic potency in M(2) receptor single-KO mice, but retained full analgesic activity in M(4) receptor single-KO mice. In contrast, two novel muscarinic agonists chemically derived from epibatidine, CMI-936 and CMI-1145, displayed reduced analgesic activity in both M(2) and M(4) receptor single-KO mice, independent of the route of application. Radioligand binding studies indicated that the two CMI compounds, in contrast to oxotremorine, showed >6-fold higher affinity for M(4) than for M(2) receptors, providing a molecular basis for the observed differences in agonist activity profiles. These data provide unambiguous evidence that muscarinic analgesia is exclusively mediated by a combination of M(2) and M(4) mAChRs at both spinal and supraspinal sites. These findings should be of considerable relevance for the development of receptor subtype-selective muscarinic agonists as novel analgesic drugs.
Collapse
Affiliation(s)
- Alokesh Duttaroy
- Laboratory of Bioorganic Chemistry, National Institute of Diabetes Digestive and Kidney Diseases, Bethesda, Maryland 20892-0810, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
11
|
Li DP, Chen SR, Pan YZ, Levey AI, Pan HL. Role of presynaptic muscarinic and GABA(B) receptors in spinal glutamate release and cholinergic analgesia in rats. J Physiol 2002; 543:807-18. [PMID: 12231640 PMCID: PMC2290545 DOI: 10.1113/jphysiol.2002.020644] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Spinally administered muscarinic receptor agonists or acetylcholinesterase inhibitors can produce effective pain relief. However, the analgesic mechanisms and the site of actions of cholinergic agents in the spinal cord are not fully understood. In this study, we investigated the mechanisms underlying cholinergic presynaptic regulation of glutamate release onto spinal dorsal horn neurons. The role of spinal GABA(B) receptors in the antinociceptive action of muscarine was also determined. Whole-cell voltage-clamp recordings were performed on visualized dorsal horn neurons in the lamina II in the spinal cord slice preparation of rats. The miniature excitatory postsynaptic currents (mEPSCs) and miniature inhibitory postsynaptic currents (mIPSCs) were recorded in the presence of tetrodotoxin. The evoked EPSCs (eEPSCs) were obtained by electrical stimulation of the dorsal root entry zone or the attached dorsal root. Nociception in rats was measured using a radiant heat stimulus and the effect of intrathecal administration of drugs tested. Acetylcholine (10-100 microM) reduced the amplitude of monosynaptic eEPSCs in a concentration-dependent manner. Acetylcholine also significantly decreased the frequency of non-NMDA receptor-mediated mEPSCs, which was antagonized by atropine but not mecamylamine. The frequency of GABA(A) receptor-mediated mIPSCs was significantly increased by acetylcholine and this excitatory effect was abolished by atropine. Existence of presynaptic M(2) muscarinic receptors in the spinal dorsal horn was further demonstrated by immunocytochemistry staining and dorsal rhizotomy. CGP55845, a GABA(B) receptor antagonist, significantly attenuated the inhibitory effect of acetylcholine on the frequency of mEPSCs and the amplitude of monosynaptic eEPSCs in lamina II neurons. Furthermore, the antinociceptive action produced by intrathecal muscarine was significantly reduced by CGP55845 pretreatment in rats. Therefore, data from this integrated study provide new information that acetylcholine inhibits the glutamatergic synaptic input to lamina II neurons through presynaptic muscarinic receptors. Inhibition of glutamate release onto lamina II neurons by presynaptic muscarinic and GABA(B) heteroreceptors in the spinal cord probably contributes to the antinociceptive action of cholinergic agents.
Collapse
Affiliation(s)
- De-Pei Li
- Department of Anesthesiology, Penn State University College of Medicine, Hershey, PA 17033, USA
| | | | | | | | | |
Collapse
|
12
|
Abstract
The actions of different cholinergic agonists and antagonists were investigated on nociceptive afferents using the rat skin-saphenous nerve preparation, in vitro. Nicotine was able to weakly excite C-nociceptors and to induce a mild sensitization to heat stimulation (in 77% of tested fibers) in a dose-dependent manner (10(-)6 to 10(-)5 m), but it caused no alteration in mechanical responsiveness tested with von Frey hairs. Muscarine did not induce a significant nociceptor excitation, but almost all fibers exhibited a marked desensitization to mechanical and heat stimuli in a dose-dependent manner (from 10(-)6 to 10(-)4 m). The muscarinic effects could be prevented by the general muscarinic antagonist scopolamine (10(-)5 m), by the M3 antagonist 1,1-dimethyl-4-diphenylacetoxypiperidium oxide (10(-)6 m) co-applied with the M2 antagonist gallamine (10(-)5 m), and by gallamine alone. As positive control we used the relatively M2-selective agonist arecaidine (10(-)6 to 10(-)5 m), obtaining a similar desensitizing effect as with muscarine. Finally, we performed an immunocytochemical study that demonstrated the presence of M2 but not M3 receptors in thin epidermal nerve fibers of the rat hairy skin. Altogether, these data demonstrate opposite effects of nicotinic and muscarinic receptor stimulation on cutaneous nociceptors. M2 receptor-mediated depression of nociceptive responsiveness may convey a therapeutic, i.e., analgesic or antinociceptive, potential.
Collapse
|
13
|
Haberberger R, Scholz R, Kummer W, Kress M. M2-receptor subtype does not mediate muscarine-induced increases in [Ca(2+)](i) in nociceptive neurons of rat dorsal root ganglia. J Neurophysiol 2000; 84:1934-41. [PMID: 11024086 DOI: 10.1152/jn.2000.84.4.1934] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Multiple muscarinic receptor subtypes are present on sensory neurons that may be involved in the modulation of nociception. In this study we focused on the presence of the muscarinic receptor subtypes, M2 and M3 (M2R, M3R), in adult rat lumbar dorsal root ganglia (DRG) at the functional ([Ca(2+)](i) measurement), transcriptional (RT-PCR), and translational level (immunohistochemistry). After 1 day in culture exposure of dissociated medium-sized neurons (20-35 micrometer diam) to muscarine was followed by rises in [Ca(2+)](i) in 76% of the neurons. The [Ca(2+)](i) increase was absent after removal of extracellular calcium and did not desensitize after repetitive application of the agonist. This rise in [Ca(2+)](i) may be explained by the expression of M3R, which can induce release of calcium from internal stores via inositoltrisphospate. Indeed the effect was antagonized by the muscarinic receptor antagonist atropine as well as by the M3R antagonist, 4-diphenylacetoxy-N-(2 chloroethyl)-piperidine hydrochloride (4-DAMP). The pharmacological identification of M3R was corroborated by RT-PCR of total RNA and single-cell RT-PCR, which revealed the presence of mRNA for M3R in lumbar DRG and in single sensory neurons. In addition, RT-PCR also revealed the expression of M2R, which did not seem to contribute to the calcium changes since it was not prevented by the M2 receptor antagonist, gallamine. Immunohistochemistry demonstrated the presence of M2R and M3R in medium-sized lumbar DRG neurons that also coexpressed binding sites for the lectin I-B4, a marker for mainly cutaneous nociceptors. The occurrence of muscarinic receptors in putative nociceptive I-B4-positive neurons suggests the involvement of these acetylcholine receptors in the modulation of processing of nociceptive stimuli.
Collapse
|