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Deng B, Zou H, Hu K, Liu Y, Han A. Octanol alleviates chronic constriction injury of sciatic nerve-induced peripheral neuropathy by regulating AKT/mTOR signaling. J Orthop Surg (Hong Kong) 2024; 32:10225536241273556. [PMID: 39208247 DOI: 10.1177/10225536241273556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 09/04/2024] Open
Abstract
OBJECTIVE Activation of gap junction channels can induce neuropathic pain. Octanol can limit the conductance of gap junctions containing connexin 43 proteins. Thus, this study focused on the roles of octanol in chronic constriction injury (CCI)-induced peripheral neuropathy in mice and its mechanisms of action. METHODS Male mice were assigned into control, sham, CCI, CCI + Octanol-20 mg/kg, CCI + Octanol-40 mg/kg and CCI + Octanol-80 mg/kg groups. CCI was performed by applying three loose ligations to mouse sciatic nerve, and the mice with CCI was administered with 20 mg/kg, 40 mg/kg, or 80 mg/kg octanol. The neuropathic pain development was examined by assessing thermal withdrawal latency, paw withdrawal mechanical threshold, and sciatic functional index. Histopathological changes were evaluated by hematoxylin and eosin staining. The phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) was examined by western blotting. The expression of Akt and mTOR was also evaluated by immunofluorescence staining. RESULTS Octanol alleviated the CCI-induced mechanical and thermal hyperalgesia and sciatic functional loss. Additionally, octanol relieved the CCI-induced abnormal histopathological changes. Mechanistically, octanol inactivated the Akt/mTOR pathway in the mice with CCI. CONCLUSION In conclusion, octanol can alleviate CCI-induced peripheral neuropathic by regulating the Akt/mTOR pathway and might be a novel pharmacological intervention for neuropathic pain.
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Affiliation(s)
- Biquan Deng
- Department of Orthopedics, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Hui Zou
- Department of Orthopedics, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Keli Hu
- Department of Orthopedics, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Yunlu Liu
- Department of Orthopedics, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
| | - Achao Han
- Department of Orthopedics, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China
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Filogonio R, Sartori MR, Morgensen S, Tavares D, Campos R, Abe AS, Taylor EW, Rodrigues GJ, De Nucci G, Simonsen U, Leite CAC, Wang T. Cholinergic regulation along the pulmonary arterial tree of the South American rattlesnake: vascular reactivity, muscarinic receptors, and vagal innervation. Am J Physiol Regul Integr Comp Physiol 2020; 319:R156-R170. [DOI: 10.1152/ajpregu.00310.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Vascular tone in the reptilian pulmonary vasculature is primarily under cholinergic, muscarinic control exerted via the vagus nerve. This control has been ascribed to a sphincter located at the arterial outflow, but we speculated whether the vascular control in the pulmonary artery is more widespread, such that responses to acetylcholine and electrical stimulation, as well as the expression of muscarinic receptors, are prevalent along its length. Working on the South American rattlesnake ( Crotalus durissus), we studied four different portions of the pulmonary artery (truncus, proximal, distal, and branches). Acetylcholine elicited robust vasoconstriction in the proximal, distal, and branch portions, but the truncus vasodilated. Electrical field stimulation (EFS) caused contractions in all segments, an effect partially blocked by atropine. We identified all five subtypes of muscarinic receptors (M1–M5). The expression of the M1 receptor was largest in the distal end and branches of the pulmonary artery, whereas expression of the muscarinic M3 receptor was markedly larger in the truncus of the pulmonary artery. Application of the neural tracer 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindo-carbocyanine perchlorate (DiI) revealed widespread innervation along the whole pulmonary artery, and retrograde transport of the same tracer indicated two separate locations in the brainstem providing vagal innervation of the pulmonary artery, the medial dorsal motor nucleus of the vagus and a ventro-lateral location, possibly constituting a nucleus ambiguus. These results revealed parasympathetic innervation of a large portion of the pulmonary artery, which is responsible for regulation of vascular conductance in C. durissus, and implied its integration with cardiorespiratory control.
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Affiliation(s)
- Renato Filogonio
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Marina R. Sartori
- Department of Zoology, State University of São Paulo, Rio Claro, São Paulo, Brazil
| | - Susie Morgensen
- Department of Biomedicine, Pulmonary, and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Driele Tavares
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Rafael Campos
- Superior Institute of Biomedical Sciences, Ceará State University, Fortaleza, Brazil
| | - Augusto S. Abe
- Department of Zoology, State University of São Paulo, Rio Claro, São Paulo, Brazil
| | - Edwin W. Taylor
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
- School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Gerson J. Rodrigues
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Gilberto De Nucci
- Faculty of Medical Sciences, Department of Pharmacology, University of Campinas, Campinas, Brazil
| | - Ulf Simonsen
- Department of Biomedicine, Pulmonary, and Cardiovascular Pharmacology, Aarhus University, Aarhus, Denmark
| | - Cléo A. C. Leite
- Department of Physiological Sciences, Federal University of São Carlos, São Carlos, Brazil
| | - Tobias Wang
- Zoophysiology, Department of Bioscience, Aarhus University, Aarhus, Denmark
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Horishita T, Ogata Y, Horishita R, Fukui R, Moriwaki K, Ueno S, Yanagihara N, Uezono Y, Sudo Y, Minami K. Carvacrol inhibits the neuronal voltage-gated sodium channels Na v1.2, Na v1.6, Na v1.3, Na v1.7, and Na v1.8 expressed in Xenopus oocytes with different potencies. J Pharmacol Sci 2020; 142:140-147. [PMID: 31982332 DOI: 10.1016/j.jphs.2019.12.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Revised: 12/07/2019] [Accepted: 12/26/2019] [Indexed: 12/19/2022] Open
Abstract
Carvacrol is the predominant monoterpene in essential oils from many aromatic plants. Several animal studies showing analgesic effects of carvacrol indicate potential of carvacrol as a new medication for patients with refractory pain. Voltage-gated sodium channels (Nav) are thought to have crucial roles in the development of inflammatory and neuropathic pain, but there is limited information about whether the analgesic mechanism of carvacrol involves Nav. We used whole-cell, two-electrode, voltage-clamp techniques to examine the effects of carvacrol on sodium currents in Xenopus oocytes expressing α subunits of Nav1.2, Nav1.3, Nav1.6, Nav1.7, and Nav1.8. Carvacrol dose-dependently suppressed sodium currents at a holding potential that induced half-maximal current. The half-maximal inhibitory concentration values for Nav1.2, Nav1.3, Nav1.6, Nav1.7, and Nav1.8 were 233, 526, 215, 367, and 824 μmol/L, respectively, indicating that carvacrol had more potent inhibitory effects towards Nav1.2 and Nav1.6 than Nav1.3, Nav1.7, and Nav1.8. Gating analysis showed a depolarizing shift of the activation curve and a hyperpolarizing shift of the inactivation curve in all five α subunits following carvacrol treatment. Furthermore, carvacrol exhibits a use-dependent block for all five α Nav subunits. These findings provide a better understanding of the mechanisms associated with the analgesic effect of carvacrol.
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Affiliation(s)
- Takafumi Horishita
- Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan.
| | - Yuichi Ogata
- Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Reiko Horishita
- Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Ryo Fukui
- Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Kuniaki Moriwaki
- Department of Anesthesiology, School of Medicine, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Susumu Ueno
- Department of Occupational Toxicology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Nobuyuki Yanagihara
- Laboratory of Pharmacology, Faculty of Food and Nutrition, Kyushu Nutrition Welfare University, Kitakyushu, Japan
| | - Yasuhito Uezono
- Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
| | - Yuka Sudo
- Department of Molecular Pathology & Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo University of Science, Chiba, Japan
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Inhibition of Gap Junction Elevates Glutamate Uptake in Cultured Astrocytes. Neurochem Res 2017; 43:59-65. [PMID: 28589517 DOI: 10.1007/s11064-017-2316-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Revised: 05/26/2017] [Accepted: 05/27/2017] [Indexed: 10/19/2022]
Abstract
Glutamate uptake is a main function of astrocytes to keep extracellular glutamate levels low and protect neurons against glutamate-induced excitotoxicity. On the other hand, astrocyte networks formed by gap junctions, which are consisted with connexins and connecting neighboring cells, are reported to play a critical role in maintaining the homeostasis in the brain. In the present study, we examined the effects of gap junction inhibitors on the glutamate uptake activity in cultured rat cortical astrocytes. At first, we confirmed the effects of gap junction inhibitors, 1-octanol and carbenoxolone, on cell-cell communication by the scrape-loading assay using a fluorescent dye Lucifer yellow. Both of 1-octanol and carbenoxolone treatments for 20 min in cultured astrocytes significantly suppressed the cell-cell communication assessed as the distance of dye-spreading. 1-octanol and carbenoxolone increased the glutamate uptake by astrocytes and glutamate aspartate transporter (GLAST) expression on the cell membrane. These results suggest that gap junction inhibitors increase the glutamate uptake activity through the increase of GLAST proteins located on the cell membrane. The regulation of gap junction in astrocytes might protect neurons against glutamate-induced excitotoxicity.
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Mikami M, Zhang Y, Kim B, Worgall TS, Groeben H, Emala CW. Dexmedetomidine's inhibitory effects on acetylcholine release from cholinergic nerves in guinea pig trachea: a mechanism that accounts for its clinical benefit during airway irritation. BMC Anesthesiol 2017; 17:52. [PMID: 28356076 PMCID: PMC5372301 DOI: 10.1186/s12871-017-0345-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2016] [Accepted: 03/21/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Airway instrumentation can evoke upper airway reflexes including bronchoconstriction and cough which can cause serious complications including airway trauma, laryngospasm or bronchospasm which may in turn lead to difficulty with ventilation and hypoxemia. These airway events are mediated in part by irritant-induced neuronal modulation of airway tone and cough responses. We investigated whether the commonly used anesthetic agents dexmedetomidine, lidocaine or remifentanil attenuated neuronal and airway smooth muscle responses in the upper airways of guinea pigs. METHODS The ability of dexmedetomidine, lidocaine or remifentanil to attenuate direct cholinergic nerve stimulation, C-fiber stimulation or direct smooth muscle contraction were studied using isolated tracheal rings from male guinea pigs under four paradigms; (1) the magnitude of contractile force elicited by cholinergic electrical field stimulation (EFS); (2) the amount of acetylcholine released during cholinergic EFS; (3) the direct airway smooth muscle relaxation of a sustained acetylcholine-induced contraction and (4) the magnitude of C-fiber mediated contraction. RESULTS Dexmedetomidine (1-100 μM) and lidocaine (1 mM) attenuated cholinergic 30Hz EFS-induced tracheal ring contraction while remifentanil (10 μM) had no effect. Dexmedetomidine at 10 μM (p = 0.0047) and 100 μM (p = 0.01) reduced cholinergic EFS-induced acetylcholine release while lidocaine (10 μM-1 mM) and remifentanil (0.1-10 μM) did not. Tracheal ring muscle force induced by the exogenous addition of the contractile agonist acetylcholine or by a prototypical C-fiber analogue of capsaicin were also attenuated by 100 μM dexmedetomidine (p = 0.0061 and p = 0.01, respectively). The actual tracheal tissue concentrations of dexmedetomidine achieved (0.54-26 nM) following buffer application of 1-100 μM of dexmedetomidine were within the range of clinically achieved plasma concentrations (12 nM). CONCLUSIONS The α2 adrenoceptor agonist dexmedetomidine reduced cholinergic EFS-induced contractions and acetylcholine release consistent with the presence of inhibitory α2 adrenoceptors on the prejunctional side of the postganglionic cholinergic nerve-smooth muscle junction. Dexmedetomidine also attenuated both exogenous acetylcholine-induced contraction and C-fiber mediated contraction, suggesting a direct airway smooth muscle effect and an underlying mechanism for cough suppression, respectively.
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Affiliation(s)
- Maya Mikami
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, P&S Box 46, New York, NY, 10032, USA.
| | - Yi Zhang
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, P&S Box 46, New York, NY, 10032, USA
| | - Benjamin Kim
- Department of Pathology and Cell Biology, College of Physicians and Surgeons of Columbia University, New York, NY, USA
| | - Tilla S Worgall
- Department of Pathology and Cell Biology, College of Physicians and Surgeons of Columbia University, New York, NY, USA
| | - Harald Groeben
- Department of Anesthesiology, Intensive Care and Pain Therapy, Kliniken Essen-Mitte, Essen, Germany
| | - Charles W Emala
- Department of Anesthesiology, College of Physicians and Surgeons of Columbia University, 630 West 168th Street, P&S Box 46, New York, NY, 10032, USA
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Kagiava A, Theophilidis G, Sargiannidou I, Kyriacou K, Kleopa KA. Oxaliplatin-induced neurotoxicity is mediated through gap junction channels and hemichannels and can be prevented by octanol. Neuropharmacology 2015; 97:289-305. [PMID: 26044641 DOI: 10.1016/j.neuropharm.2015.05.021] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 04/16/2015] [Accepted: 05/16/2015] [Indexed: 12/22/2022]
Abstract
Oxaliplatin-induced neurotoxicity (OIN) is a common complication of chemotherapy without effective treatment. In order to clarify the mechanisms of both acute and chronic OIN, we used an ex-vivo mouse sciatic nerve model. Exposure to 25 μM oxaliplatin caused a marked prolongation in the duration of the nerve evoked compound action potential (CAP) by nearly 1200% within 300 min while amplitude remained constant for over 20 h. This oxaliplatin effect was almost completely reversed by the gap junction (GJ) inhibitor octanol in a concentration-dependent manner. Further GJ blockers showed similar effects although with a narrower therapeutic window. To clarify the target molecule we studied sciatic nerves from connexin32 (Cx32) and Cx29 knockout (KO) mice. The oxaliplatin effect and neuroprotection by octanol partially persisted in Cx29 better than in Cx32 KO nerves, suggesting that oxaliplatin affects both, but Cx32 GJ channels more than Cx29 hemichannels. Oxaliplatin also accelerated neurobiotin uptake in HeLa cells expressing the human ortholog of Cx29, Cx31.3, as well as dye transfer between cells expressing the human Cx32, and this effect was blocked by octanol. Oxaliplatin caused no morphological changes initially (up to 3 h of exposure), but prolonged nerve exposure caused juxtaparonodal axonal edema, which was prevented by octanol. Our study indicates that oxaliplatin causes forced opening of Cx32 channels and Cx29 hemichannels in peripheral myelinated fibers leading to disruption of axonal K(+) homeostasis. The GJ blocker octanol prevents OIN at very low concentrations and should be further studied as a neuroprotectant.
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Affiliation(s)
- Alexia Kagiava
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - George Theophilidis
- Laboratory of Animal Physiology, Department of Zoology, School of Biology, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Irene Sargiannidou
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kyriacos Kyriacou
- Department of Molecular Pathology and Electron Microscopy, The Cyprus Institute of Neurology and Genetics, Cyprus School of Molecular Medicine, Nicosia, Cyprus
| | - Kleopas A Kleopa
- Neuroscience Laboratory, The Cyprus Institute of Neurology and Genetics, Cyprus School of Molecular Medicine, Nicosia, Cyprus; Neurology Clinics, The Cyprus Institute of Neurology and Genetics, Cyprus School of Molecular Medicine, Nicosia, Cyprus.
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Okura D, Horishita T, Ueno S, Yanagihara N, Sudo Y, Uezono Y, Sata T. The endocannabinoid anandamide inhibits voltage-gated sodium channels Nav1.2, Nav1.6, Nav1.7, and Nav1.8 in Xenopus oocytes. Anesth Analg 2014; 118:554-62. [PMID: 24557103 DOI: 10.1213/ane.0000000000000070] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
BACKGROUND Anandamide is an endocannabinoid that regulates multiple physiological functions by pharmacological actions, in a manner similar to marijuana. Recently, much attention has been paid to the analgesic effect of endocannabinoids in terms of identifying new pharmacotherapies for refractory pain management, but the mechanisms of the analgesic effects of anandamide are still obscure. Voltage-gated sodium channels are believed to play important roles in inflammatory and neuropathic pain. We investigated the effects of anandamide on 4 neuronal sodium channel α subunits, Nav1.2, Nav1.6, Nav1.7, and Nav1.8, to explore the mechanisms underlying the antinociceptive effects of anandamide. METHODS We studied the effects of anandamide on Nav1.2, Nav1.6, Nav1.7, and Nav1.8 α subunits with β1 subunits by using whole-cell, 2-electrode, voltage-clamp techniques in Xenopus oocytes. RESULTS Anandamide inhibited sodium currents of all subunits at a holding potential causing half-maximal current (V1/2) in a concentration-dependent manner. The half-maximal inhibitory concentration values for Nav1.2, Nav1.6, Nav1.7, and Nav1.8 were 17, 12, 27, and 40 μmol/L, respectively, indicating an inhibitory effect on Nav1.6, which showed the highest potency. Anandamide raised the depolarizing shift of the activation curve as well as the hyperpolarizing shift of the inactivation curve in all α subunits, suggesting that sodium current inhibition was due to decreased activation and increased inactivation. Moreover, anandamide showed a use-dependent block in Nav1.2, Nav1.6, and Nav1.7 but not Nav1.8. CONCLUSION Anandamide inhibited the function of α subunits in neuronal sodium channels Nav1.2, Nav1.6, Nav1.7, and Nav1.8. These results help clarify the mechanisms of the analgesic effects of anandamide.
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Affiliation(s)
- Dan Okura
- From the *Department of Anesthesiology, School of Medicine; †Department of Occupational Toxicology, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, ‡Department of Pharmacology, School of Medicine, University of Occupational and Environmental Health, Fukuoka; §Department of Molecular Pathology & Metabolic Disease, Faculty of Pharmaceutical Sciences, Tokyo university of Science, Chiba; and ‖Cancer Pathophysiology Division, National Cancer Center Research Institute, Tokyo, Japan
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Obreja O, Hirth M, Turnquist B, Rukwied R, Ringkamp M, Schmelz M. The Differential Effects of Two Sodium Channel Modulators on the Conductive Properties of C-Fibers in Pig Skin In Vivo. Anesth Analg 2012; 115:560-71. [DOI: 10.1213/ane.0b013e3182542843] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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A model system to study Connexin 43 in the immune system. Mol Immunol 2009; 46:2938-46. [PMID: 19608277 DOI: 10.1016/j.molimm.2009.06.022] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2009] [Revised: 06/11/2009] [Accepted: 06/18/2009] [Indexed: 11/21/2022]
Abstract
Connexin 43 (Cx43) is the predominant gap junction protein expressed in immune cells. Previous manuscripts have stated that gap junctions may play a role in antigen cross-presentation, dendritic cell maturation, T cell development, and regulatory T cell function. Many of these previous studies were performed in vitro. In vivo studies were not directly possible in adult mice because Cx43-/- mice die shortly after birth due to a cardiac malformation. To overcome these drawbacks, we have developed a mouse model that deletes Cx43 in the immune system while maintaining normal cardiac function. In our model, irradiated CD45.1+ wild-type mice were reconstituted with Cx43WT, Cx43+/-, or Cx43-/- hematopoietic fetal liver cells that were derived from CD45.2+ mice. The presence of CD45.2 allowed us to identify and track the donor cells following reconstitution. We determined that Cx43+/- and Cx43-/- hematopoietic cells were able to reconstitute irradiated mice as well as Cx43WT cells. Reconstitution was nearly 100% in the thymus and over 90% in the spleen. There appeared to be no difference in thymocyte development or in the ability of lymphocytes to transmigrate to peripheral lymphoid organs. However in response to inflammation, Cx43+/- radiation chimeras had increased peritoneal infiltration compared to Cx43WT and Cx43-/- groups. IgG responses were normal in all groups but the Cx43-/- reconstituted mice had an elevated IgM response. Our data suggests that Cx43 may not be involved in the normal development of the immune system but may regulate certain effector functions in vivo.
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Suadicani SO, Brosnan CF, Scemes E. P2X7 receptors mediate ATP release and amplification of astrocytic intercellular Ca2+ signaling. J Neurosci 2006; 26:1378-85. [PMID: 16452661 PMCID: PMC2586295 DOI: 10.1523/jneurosci.3902-05.2006] [Citation(s) in RCA: 422] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Modulation of synaptic transmission and brain microcirculation are new roles ascribed to astrocytes in CNS function. A mechanism by which astrocytes modify neuronal activity in the healthy brain depends on fluctuations of cytosolic Ca2+ levels, which regulate the release of "gliotransmitters" via an exocytic pathway. Under pathological conditions, however, the participation of other pathways, including connexin hemichannels and the pore-forming P2X7R, have been proposed but remain controversial. Through the use of genetically modified 1321N1 human astrocytoma cells and of spinal cord astrocytes derived from neonatal Cx43- and P2X7R-null mice, we provide strong evidence that P2X7Rs, but not Cx43 hemichannels, are sites of ATP release that promote the amplification of Ca2+ signal transmission within the astrocytic network after exposure to low divalent cation solution. Moreover, our results showing that gap junction channel blockers (heptanol, octanol, carbenoxolone, flufenamic acid, and mefloquine) are antagonists of the P2X7R indicate the inadequacy of using these compounds as evidence for the participation of connexin hemichannels as sites of gliotransmitter release.
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Affiliation(s)
- Sylvia O Suadicani
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
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11
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Moss BL, Fuller AD, Sahley CL, Burrell BD. Serotonin modulates axo-axonal coupling between neurons critical for learning in the leech. J Neurophysiol 2005; 94:2575-89. [PMID: 15987763 DOI: 10.1152/jn.00322.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
S cells form a chain of electrically coupled neurons that extends the length of the leech CNS and plays a critical role in sensitization during whole-body shortening. This process requires serotonin, which acts in part by altering the pattern of activity in the S-cell network. Serotonin-containing axons and varicosities were observed in Faivre's nerve where the S-to-S-cell electrical synapses are located. To determine whether serotonin modulates these synapses, S-cell action-potential (AP) propagation was studied in a two-ganglion chain containing one electrical synapse. Suction electrodes were placed on the cut ends of the connectives to stimulate one S cell while recording the other, coupled S cell's APs. A third electrode, placed en passant, recorded the APs near the electrical synapse before they propagated through it. Low concentrations of the gap junction inhibitor octanol increased AP latency across the two-ganglion chain, and this effect was localized to the region of axon containing the electrical synapse. At higher concentrations, APs failed to propagate across the synapse. Serotonin also increased AP latency across the electrical synapse, suggesting that serotonin reduced coupling between S cells. This effect was independent of the direction of propagation and increased with the number of electrical synapses in progressively longer chains. Furthermore, serotonin modulated instantaneous AP frequency when APs were initiated in separate S cells and in a computational model of S-cell activity after mechanosensory input. Thus serotonergic modulation of S-cell electrical synapses may contribute to changes in the pattern of activity in the S-cell network.
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Affiliation(s)
- Brenda L Moss
- Neuroscience Group, Division of Basic Biomedical Sciences, University of South Dakota School of Medicine, Vermillion, 57069, USA
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Inghilleri M, Conte A, Frasca V, Gilio F, Lorenzano C, Berardelli A. Synaptic potentiation induced by rTMS: effect of lidocaine infusion. Exp Brain Res 2005; 163:114-7. [PMID: 15940502 DOI: 10.1007/s00221-005-2225-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2004] [Accepted: 12/09/2004] [Indexed: 01/04/2023]
Abstract
Repetitive transcranial magnetic stimulation (rTMS) delivered at various intensities and frequencies excites cortical motor areas. Trains of stimuli (at 5-Hz frequency, and suprathreshold intensity) progressively increase the size of motor evoked potentials (MEPs) and the duration of the cortical silent period (CSP) in normal subjects. Because antiepileptic drugs, acting mainly on sodium channels, depress MEP facilitation during rTMS, we suggested that rTMS trains facilitate the MEP size by inducing synaptic potentiation primarily involving voltage-gated sodium channels. The aim of this study was to evaluate the effect of lidocaine-a drug that acts selectively on sodium channels-on the rTMS-induced changes in cortical excitability. We tested the changes in motor threshold, MEP size, CSP duration evoked by focal rTMS and the M-wave amplitude in healthy subjects before and after lidocaine infusion. Lidocaine abolished the normal rTMS-induced facilitation of MEPs but left the other rTMS variables and the M-wave unchanged. Our results suggest that the MEP facilitation related to rTMS-induced synaptic potentiation results from an increase in cortical excitatory interneuron excitability that involves voltage-gated sodium channels.
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Affiliation(s)
- M Inghilleri
- Department of Neurological Sciences, University of Rome La Sapienza, Viale dell'Università, 30., 00185 Rome, Italy.
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13
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Abstract
PURPOSE OF REVIEW In recent years there has been a renewed interest in regional anaesthesia, particularly peripheral nerve blockade, not only to improve the patient's well being, but also to meet the requirements of modern orthopaedic surgery. Nerve injury in this context is the complication most feared by the patient, the anaesthesiologist and the surgeon. RECENT FINDINGS To date, data dealing with the incidence of nerve injury in regional anaesthesia have almost exclusively been retrieved from close claims analysis. Recently, prospective, well controlled studies have shown that severe neurologic complications rarely occur: for the upper extremity, an incidence of 0.2-1% has been reported. New insights into the mechanisms of local anaesthetic neurotoxicity have demonstrated that ropivacaine has the least potential for neurotoxicity. Administration of the lowest possible concentrated solution of local anaesthetic is likely to be even less neurotoxic. The role of local anaesthetics in the development of apoptosis is nowadays well recognized. The consequences of other factors, such as nerve stretching and compression, in the pathology of nerve damage are emphasized. SUMMARY Significant advances have been made in regional anaesthesia in the past 10 years. The introduction of catheter techniques has cleared the way for better regional anaesthetic and analgesic blocks. Studies dealing with placement of perineural catheters show that the catheter does not increase neurological complications. Properly performed, regional anaesthesia is a safe form of anaesthesia and the benefits far outweigh the risks.
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Affiliation(s)
- Alain Borgeat
- Department of Anaesthesia, Orthopaedic University Hospital Balgrist, Zurich, Switzerland.
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