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Sun W, Yang F, Wang Y, Yang Y, Du R, Wang XL, Luo ZX, Wu JJ, Chen J. Sortilin-Mediated Inhibition of TREK1/2 Channels in Primary Sensory Neurons Promotes Prediabetic Neuropathic Pain. Adv Sci (Weinh) 2024:e2310295. [PMID: 38626370 DOI: 10.1002/advs.202310295] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2023] [Revised: 03/29/2024] [Indexed: 04/18/2024]
Abstract
Neuropathic pain can occur during the prediabetic stage, even in the absence of hyperglycemia. The presence of prediabetic neuropathic pain (PDNP) poses challenges to the management of individuals with prediabetes. However, the mechanisms underlying this pain remain unclear. This study aims to investigate the underlying mechanism and identify potential therapeutic targets of PDNP. A prediabetic animal model induced by a high-energy diet exhibits both mechanical allodynia and thermal hyperalgesia. Furthermore, hyperexcitability and decreased potassium currents are observed in the dorsal root ganglion (DRG) neurons of these rats. TREK1 and TREK2 channels, which belong to the two-pore-domain K+ channel (K2P) family and play an important role in controlling cellular excitability, are downregulated in DRG neurons. Moreover, this alteration is modulated by Sortilin, a molecular partner that modulates the expression of TREK1. The overexpression of Sortilin negatively affects the expression of TREK1 and TREK2, leading to increased neuronal excitability in the DRG and enhanced peripheral pain sensitivity in rats. Moreover, the downregulation of Sortilin or activation of TREK1 and TREK2 channels by genetic or pharmacological approaches can alleviate PDNP. Therefore, targeting the Sortilin-mediated TREK1/2 pathway may provide a therapeutic approach for ameliorating PDNP.
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Affiliation(s)
- Wei Sun
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Fan Yang
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Yan Wang
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Yan Yang
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Rui Du
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Xiao-Liang Wang
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Zhi-Xin Luo
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
| | - Jun-Jie Wu
- State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, National Clinical Research Center for Oral Diseases, Shaanxi Key Laboratory of Stomatology, Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710032, P. R. China
| | - Jun Chen
- Institute for Biomedical Sciences of Pain, Tangdu Hospital, The Fourth Military Medical University, Xi'an, Shaanxi Province, 710038, P. R. China
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Sun H, Patil MJ, Ru F, Meeker S, Undem BJ. K
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1/D‐type potassium channels inhibit the excitability of bronchopulmonary vagal afferent nerves. J Physiol 2022; 600:2953-2971. [PMID: 35430729 PMCID: PMC9203938 DOI: 10.1113/jp282803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2022] [Accepted: 04/04/2022] [Indexed: 11/10/2022] Open
Abstract
Abstract The KV1/D‐type potassium current (ID) is an important determinant of neuronal excitability. This study explored whether and how ID channels regulate the activation of bronchopulmonary vagal afferent nerves. The single‐neuron RT‐PCR assay revealed that nearly all mouse bronchopulmonary nodose neurons expressed the transcripts of α‐dendrotoxin (α‐DTX)‐sensitive, ID channel‐forming KV1.1, KV1.2 and/or KV1.6 α‐subunits, with the expression of KV1.6 being most prevalent. Patch‐clamp recordings showed that ID, defined as the α‐DTX‐sensitive K+ current, activated at voltages slightly more negative than the resting membrane potential in lung‐specific nodose neurons and displayed little inactivation at subthreshold voltages. Inhibition of ID channels by α‐DTX depolarized the lung‐specific nodose neurons and caused an increase in input resistance, decrease in rheobase, as well as increase in action potential number and firing frequency in response to suprathreshold current steps. Application of α‐DTX to the lungs via trachea in the mouse ex vivo vagally innervated trachea–lungs preparation led to action potential discharges in nearly half of bronchopulmonary nodose afferent nerve fibres, including nodose C‐fibres, as detected by the two‐photon microscopic Ca2+ imaging technique and extracellular electrophysiological recordings. In conclusion, ID channels act as a critical brake on the activation of bronchopulmonary vagal afferent nerves by stabilizing the membrane potential, counterbalancing the subthreshold depolarization and promoting the adaptation of action potential firings. Down‐regulation of ID channels, as occurs in various inflammatory diseases, may contribute to the enhanced C‐fibre activity in airway diseases that are associated with excessive coughing, dyspnoea, and reflex bronchospasm and secretions. Key points The α‐dendrotoxin (α‐DTX)‐sensitive D‐type K+ current (ID) is an important determinant of neuronal excitability. Nearly all bronchopulmonary nodose afferent neurons in the mouse express ID and the transcripts of α‐DTX‐sensitive, ID channel‐forming KV1.1, KV1.2 and/or KV1.6 α‐subunits. Inhibition of ID channels by α‐DTX depolarizes the bronchopulmonary nodose neurons, reduces the minimal depolarizing current needed to evoke an action potential (AP) and increases AP number and AP firing frequency in response to suprathreshold stimulations. Application of α‐DTX to the lungs ex vivo elicits AP discharges in about half of bronchopulmonary nodose C‐fibre terminals.
Our novel finding that ID channels act as a critical brake on the activation of bronchopulmonary vagal afferent nerves suggests that their down‐regulation, as occurs in various inflammatory diseases, may contribute to the enhanced C‐fibre activity in airway inflammation associated with excessive respiratory symptoms.
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Affiliation(s)
- Hui Sun
- Division of Allergy and Clinical Immunology Department of Medicine Johns Hopkins University School of Medicine 5501 Hopkins Bayview Circle Baltimore 21224
| | - Mayur J. Patil
- Division of Allergy and Clinical Immunology Department of Medicine Johns Hopkins University School of Medicine 5501 Hopkins Bayview Circle Baltimore 21224
| | - Fei Ru
- Division of Allergy and Clinical Immunology Department of Medicine Johns Hopkins University School of Medicine 5501 Hopkins Bayview Circle Baltimore 21224
| | - Sonya Meeker
- Division of Allergy and Clinical Immunology Department of Medicine Johns Hopkins University School of Medicine 5501 Hopkins Bayview Circle Baltimore 21224
| | - Bradley J. Undem
- Division of Allergy and Clinical Immunology Department of Medicine Johns Hopkins University School of Medicine 5501 Hopkins Bayview Circle Baltimore 21224
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Suda M, Takatsuru Y, Amano I, Haraguchi S, Koibuchi N. Adult-onset hypothyroidism causes mechanical hypersensitivity due to peripheral nerve hyperexcitability based on voltage-gated potassium channel downregulation in male mice. J Neurosci Res 2021; 100:506-521. [PMID: 34935172 DOI: 10.1002/jnr.25001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 07/21/2021] [Accepted: 10/21/2021] [Indexed: 11/09/2022]
Abstract
Thyroid hormones play an important role in the central and peripheral nervous system functions. Approximately 50% of adult-onset hypothyroid patients have sensory symptoms including pain, possibly caused by peripheral neuropathy. However, the mechanism causing the pain has not been clarified. We generated an adult-onset hypothyroid model animal by administering 50 ppm propylthiouracil (PTU) for 5 weeks to male mice. Female mice were not tested in this study. Mechanical hypersensitivity, determined by the von Frey hair test, was observed during the PTU exposure and recovered after the exposure termination. The sciatic nerve compound action potential was also analyzed. Under single-pulse stimulation, no significant change in the threshold and conduction velocity was observed in the PTU-administered group. On the other hand, under train-pulse stimulation, the latency delay in the Aδ-fiber component was less in the PTU-administered group in Week 4 of PTU exposure, indicating relative hyperexcitability. Fluticasone, which is the anti-inflammatory agent with an ability to activate the voltage-gated potassium channel subfamily A (Kv1), restored the decrease in the latency change ratio by PTU exposure under the train-pulse stimulation supporting our hypothesis that Kv1 may be involved in the conductivity change. Kv1.1 protein level decreased significantly in the sciatic nerve of the PTU-administered group. These results indicate that adult-onset hypothyroidism causes mechanical hypersensitivity owing to hyperexcitability of the peripheral nerve and that reduction of Kv1.1 level may be involved in such alteration.
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Affiliation(s)
- Machiko Suda
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Yusuke Takatsuru
- Department of Nutrition and Health Science, Toyo University, Ora-gun, Japan
| | - Izuki Amano
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
| | - Shogo Haraguchi
- Department of Biochemistry, Showa University School of Medicine, Shinagawa-ku, Japan
| | - Noriyuki Koibuchi
- Department of Integrative Physiology, Gunma University Graduate School of Medicine, Maebashi, Japan
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Hong J, Qiu J, Wang X, Zhang G. Characteristics of voltage-gated potassium currents in monosodium urate induced gouty arthritis in mice. Inflamm Res 2020; 69:589-598. [PMID: 32306120 DOI: 10.1007/s00011-020-01343-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Revised: 01/15/2020] [Accepted: 03/26/2020] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVE To evaluate the role of K+ channels in pain following gouty arthritis. METHODS The model of acute gouty arthritis was induced by monosodium urate (MSU) in mice. The swelling degree was determined by measuring the circumference of the ankle joint. Mechanical hyperalgesia was detected by von Frey filaments. Two types of K+ currents, A-type currents (IA) and delayed rectifier currents (IK), were recorded in dorsal root ganglion (DRG) neurons using patch-clamp techniques. RESULTS The swelling degree reached its maximum at 10 h and the minimum pain threshold was maintained between 8 and 48 h after MSU treatment in mice. The amplitudes of IA and IK in DRG neurons were moderately increased on day 1 after MSU treatment, and then, they were gradually decreased with times and reached their minimums on day 4 (for IA) or 5 (for IK). Compared with control group, the activation curve of IA was significantly shifted to more positive potential and the recovery time of IA from inactivation was markedly prolonged, but inactivation and frequency dependence of IA appeared unaffected in MSU-treated group. Additionally, no change was observed in the activation curve of IK after MSU treatment. The excitability was significantly higher in the MSU group than in the control group. CONCLUSIONS MSU-induced gout pain may be related to the hyperexcitability of DRG neurons elicited by decreasing K+ currents.
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Affiliation(s)
- Jiangru Hong
- Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Jie Qiu
- Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Xiniao Wang
- Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China
| | - Guangqin Zhang
- Department of Clinical Pharmacy, China Pharmaceutical University, Nanjing, 210009, China.
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Zhang X, Gu H, Ma K. Dynamical mechanism for conduction failure behavior of action potentials related to pain information transmission. Neurocomputing 2020; 387:293-308. [DOI: 10.1016/j.neucom.2019.12.114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Schiller AM, Hong J, Xia Z, Wang HJ. Increased Brain-Derived Neurotrophic Factor in Lumbar Dorsal Root Ganglia Contributes to the Enhanced Exercise Pressor Reflex in Heart Failure. Int J Mol Sci 2019; 20:E1480. [PMID: 30909643 DOI: 10.3390/ijms20061480] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2019] [Revised: 03/20/2019] [Accepted: 03/21/2019] [Indexed: 12/25/2022] Open
Abstract
An exaggerated exercise pressor reflex (EPR) is associated with excessive sympatho-excitation and exercise intolerance in the chronic heart failure (CHF) state. We hypothesized that brain-derived neurotrophic factor (BDNF) causes the exaggerated EPR via sensitizing muscle mechanosensitive afferents in CHF. Increased BDNF expression was observed in lumbar dorsal root ganglia (DRGs) from CHF rats compared to sham rats. Immunofluorescence data showed a greater increase in the number of BDNF-positive neurons in medium and large-sized DRG subpopulations from CHF rats. Patch clamp data showed that incubation with BDNF for 4–6 h, significantly decreased the current threshold-inducing action potential (AP), threshold potential and the number of APs during current injection in Dil-labeled isolectin B4 (IB4)-negative medium-sized DRG neurons (mainly mechano-sensitive) from sham rats. Compared to sham rats, CHF rats exhibited an increased number of APs during current injection in the same DRG subpopulation, which was significantly attenuated by 4-h incubation with anti-BDNF. Finally, chronic epidural delivery of anti-BDNF attenuated the exaggerated pressor response to either static contraction or passive stretch in CHF rats whereas this intervention had no effect on the pressor response to hindlimb arterial injection of capsaicin. These data suggest that increased BDNF in lumbar DRGs contributes to the exaggerated EPR in CHF.
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Sforna L, Franciolini F, Catacuzzeno L. Ca 2+ -dependent and Ca 2+ -independent somatic release from trigeminal neurons. J Cell Physiol 2018; 234:10977-10989. [PMID: 30536400 DOI: 10.1002/jcp.27901] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 10/25/2018] [Indexed: 01/03/2023]
Abstract
Besides the nerve endings, the soma of trigeminal neurons also respond to membrane depolarizations with the release of neurotransmitters and neuromodulators in the extracellular space within the ganglion, a process potentially important for the cross-communication between neighboring sensory neurons. In this study, we addressed the dependence of somatic release on Ca2+ influx in trigeminal neurons and the involvement of the different types of voltage-gated Ca2+ (Cav) channels in the process. Similar to the closely related dorsal root ganglion neurons, we found two kinetically distinct components of somatic release, a faster component stimulated by voltage but independent of the Ca2+ influx, and a slower component triggered by Ca2+ influx. The Ca2+ -dependent component was inhibited 80% by ω-conotoxin-MVIIC, an inhibitor of both N- and P/Q-type Cav channels, and 55% by the P/Q-type selective inhibitor ω-agatoxin-IVA. The selective L-type Ca2+ channel inhibitor nimodipine was instead without effect. These results suggest a major involvement of N- and P/Q-, but not L-type Cav channels in the somatic release of trigeminal neurons. Thus antinociceptive Cav channel antagonists acting on the N- and P/Q-type channels may exert their function by also modulating the somatic release and cross-communication between sensory neurons.
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Affiliation(s)
- Luigi Sforna
- Department of Chemistry, Biology, and Biotechnology, University of Perugia, Perugia, Italy
- Department of Experimental Medicine, University of Perugia, Perugia, Italy
| | - Fabio Franciolini
- Department of Chemistry, Biology, and Biotechnology, University of Perugia, Perugia, Italy
| | - Luigi Catacuzzeno
- Department of Chemistry, Biology, and Biotechnology, University of Perugia, Perugia, Italy
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Abstract
The firing properties of small neurons (with diameters of soma less than 25 µm) were investigated using patch-clamp technique in whole-cell configuration in primary culture of trigeminal ganglia (TG) of postnatal rats. TG neurons were divided into three groups according to their firing responses to long-lasting depolarizing pulses: adaptive neurons (AN) characterized by a strongly adaptive responses; tonic neurons (TN) characterized by a multiple tonic firing; neurons with a delay before initiation of AP generation, namely, NDG. AN, TN and NDG also differed in AP electrophysiological and pharmacological characteristics. TN was distinguished by responses to hyperpolarization and the greatest value of input resistance. TN, AN and NDG were characterized by different active properties (amplitude of action potential and afterhyperpolarization, reobase, threshold). Each group of neurons was characterized by heterogeneity of AP duration and of frequency properties for TN. The application of tetrodotoxin (TTX) (250 nM) resulted in full or partial inhibition of AP generation and some neurons had TTX – insensitive firing responses. Neurons that were not affected by TTX had markedly longer AP. TTX had no effect on electrical activity of some AN and NDG. Based on sensitivity to TTX and their electrophysiological properties, AN and NDG seem to be C-fiber nococeptors.
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Wang H, Xiao C, Dong D, Lin C, Xue Y, Liu J, Wu M, He J, Fu T, Pan H, Jiao X, Lu D, Li Z. Epothilone B Speeds Corneal Nerve Regrowth and Functional Recovery through Microtubule Stabilization and Increased Nerve Beading. Sci Rep 2018; 8:2647. [PMID: 29422528 PMCID: PMC5805685 DOI: 10.1038/s41598-018-20734-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2017] [Accepted: 01/23/2018] [Indexed: 12/13/2022] Open
Abstract
The successful restoration of corneal innervation and function after a corneal injury is a clinically challenging issue. Structural and functional recovery after a nerve injury involves a complex series of steps in which microtubules play a key role. The aim of the current study was to investigate the effects of epothilone B (EpoB), a microtubule-stabilizing agent, on corneal innervation and the functional recovery of the corneal nerve in mice after corneal epithelial abrasion. The pretreatment of mice with EpoB has a remarkable effect on the stabilization of beta-III tubulin, as demonstrated by substantial increases in the visualization of beta-III tubulin, nerve beading, corneal reinnervation, and reaction to stimuli. Furthermore, a pharmacokinetic analysis showed that EpoB remains at a high concentration in the cornea and the trigeminal ganglion for at least 6 days after administration. In addition, the administration of EpoB at 24 hours after corneal abrasion has a marked therapeutic effect on nerve regrowth and functional recovery. In conclusion, EpoB treatment may have therapeutic utility for improving corneal reinnervation and restoring sensitivity following corneal injury.
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Affiliation(s)
- Hanqing Wang
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Chengju Xiao
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Dong Dong
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Cuipei Lin
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Yunxia Xue
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Jun Liu
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Mingjuan Wu
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Jingxin He
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Ting Fu
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Hongwei Pan
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China
| | - Xinwei Jiao
- Henan Key Laboratory of Ophthalmology and Visual Science, People's Hospital of Zhengzhou University, Henan University School of Medicine, Henan Provincial People's Hospital, Zhengzhou, China
| | - Dingli Lu
- Henan Key Laboratory of Ophthalmology and Visual Science, People's Hospital of Zhengzhou University, Henan University School of Medicine, Henan Provincial People's Hospital, Zhengzhou, China
| | - Zhijie Li
- International Ocular Surface Research Center, Institute of Ophthalmology, Key Laboratory for Regenerative Medicine of the Ministry of Education, Jinan University, Guangzhou, China. .,Henan Key Laboratory of Ophthalmology and Visual Science, People's Hospital of Zhengzhou University, Henan University School of Medicine, Henan Provincial People's Hospital, Zhengzhou, China. .,Department of Immunology and Microbiology, Jinan University Medical School, Guangzhou, China. .,Section of Leukocyte Biology, Department of Pediatrics, Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas, USA.
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Watanabe T, Shimazaki T, Oda Y. Coordinated Expression of Two Types of Low-Threshold K + Channels Establishes Unique Single Spiking of Mauthner Cells among Segmentally Homologous Neurons in the Zebrafish Hindbrain. eNeuro 2017; 4:ENEURO. [PMID: 29085904 DOI: 10.1523/ENEURO.0249-17.2017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2017] [Revised: 09/28/2017] [Accepted: 09/29/2017] [Indexed: 01/15/2023] Open
Abstract
Expression of different ion channels permits homologously-generated neurons to acquire different types of excitability and thus code various kinds of input information. Mauthner (M) series neurons in the teleost hindbrain consist of M cells and their morphological homologs, which are repeated in adjacent segments and share auditory inputs. When excited, M cells generate a single spike at the onset of abrupt stimuli, while their homologs encode input intensity with firing frequency. Our previous study in zebrafish showed that immature M cells burst phasically at 2 d postfertilization (dpf) and acquire single spiking at 4 dpf by specific expression of auxiliary Kvβ2 subunits in M cells in association with common expression of Kv1.1 channels in the M series. Here, we further reveal the ionic mechanisms underlying this functional differentiation. Pharmacological blocking of Kv7/KCNQ in addition to Kv1 altered mature M cells to fire tonically, similar to the homologs. In contrast, blocking either channel alone caused M cells to burst phasically. M cells at 2 dpf fired tonically after blocking Kv7. In situ hybridization revealed specific Kv7.4/KCNQ4 expression in M cells at 2 dpf. Kv7.4 and Kv1.1 channels expressed in Xenopus oocytes exhibited low-threshold outward currents with slow and fast rise times, while coexpression of Kvβ2 accelerated and increased Kv1.1 currents, respectively. Computational models, modified from a mouse cochlear neuron model, demonstrated that Kv7.4 channels suppress repetitive firing to produce spike-frequency adaptation, while Kvβ2-associated Kv1.1 channels increase firing threshold and decrease the onset latency of spiking. Altogether, coordinated expression of these low-threshold K+ channels with Kvβ2 functionally differentiates M cells among homologous neurons.
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de Moraes ER, Kushmerick C, Naves LA. Morphological and functional diversity of first-order somatosensory neurons. Biophys Rev 2017; 9:847-856. [PMID: 28889335 DOI: 10.1007/s12551-017-0321-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Accepted: 08/24/2017] [Indexed: 01/01/2023] Open
Abstract
First-order somatosensory neurons transduce and convey information about the external or internal environment of the body to the central nervous system. They are pseudo unipolar neurons with cell bodies residing in one of several ganglia located near the central nervous system, with the short branch of the axon connecting to the spinal cord or the brain stem and the long branch extending towards the peripheral organ they innervate. Besides their sensory transducer and conductive role, somatosensory neurons also have trophic functions in the tissue they innervate and participate in local reflexes in the periphery. The cell bodies of these neurons are remarkably diverse in terms of size, molecular constitution, and electrophysiological properties. These parameters have provided criteria for classification that have proved useful to establish and study their functions. In this review, we discuss ways to measure and classify populations of neurons based on their size and action potential firing pattern. We also discuss attempts to relate the different populations to specific sensory modalities.
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Affiliation(s)
- Eder Ricardo de Moraes
- Departamento de Fisiologia, Centro de Ciências Biológicas e da Saúde, Universidade Federal de Sergipe, São Cristóvão, Sergipe, Brazil
| | - Christopher Kushmerick
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil
| | - Lígia Araujo Naves
- Departamento de Fisiologia e Biofísica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil.
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Marchenkova A, van den Maagdenberg AMJM, Nistri A. Loss of inhibition by brain natriuretic peptide over P2X3 receptors contributes to enhanced spike firing of trigeminal ganglion neurons in a mouse model of familial hemiplegic migraine type-1. Neuroscience 2016; 331:197-205. [PMID: 27346147 DOI: 10.1016/j.neuroscience.2016.06.034] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 06/16/2016] [Accepted: 06/18/2016] [Indexed: 11/26/2022]
Abstract
Purinergic P2X3 receptors (P2X3Rs) play an important role in pain pathologies, including migraine. In trigeminal neurons, P2X3Rs are constitutively downregulated by endogenous brain natriuretic peptide (BNP). In a mouse knock-in (KI) model of familial hemiplegic migraine type-1 with upregulated calcium CaV2.1 channel function, trigeminal neurons exhibit hyperexcitability with gain-of-function of P2X3Rs and their deficient BNP-mediated inhibition. We studied whether the absent BNP-induced control over P2X3Rs activity in KI cultures may be functionally expressed in altered firing activity of KI trigeminal neurons. Patch-clamp experiments investigated the excitability of wild-type and KI trigeminal neurons induced by either current or agonists for P2X3Rs or transient receptor potential vanilloid-1 (TRPV1) receptors. Consistent with the constitutive inhibition of P2X3Rs by BNP, sustained pharmacological block of BNP receptors selectively enhanced P2X3R-mediated excitability of wild-type neurons without affecting firing evoked by the other protocols. This effect included increased number of action potentials, lower spike threshold and shift of the firing pattern distribution toward higher spiking activity. Thus, inactivation of BNP signaling transformed the wild-type excitability phenotype into the one typical for KI. BNP receptor block did not influence excitability of KI neurons in accordance with the lack of BNP-induced P2X3R modulation. Our study suggests that, in wild-type trigeminal neurons, negative control over P2X3Rs by the BNP pathway is translated into tonic suppression of P2X3Rs-mediated excitability. Lack of this inhibition in KI cultures results in a hyperexcitability phenotype and might contribute to facilitated trigeminal pain transduction relevant for migraine.
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Affiliation(s)
- Anna Marchenkova
- Neuroscience Department, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
| | - Arn M J M van den Maagdenberg
- Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands; Department of Human Genetics, University Medical Centre, Leiden, Netherlands.
| | - Andrea Nistri
- Neuroscience Department, International School for Advanced Studies (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
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D'Adamo MC, Sforna L, Visentin S, Grottesi A, Servettini L, Guglielmi L, Macchioni L, Saredi S, Curcio M, De Nuccio C, Hasan S, Corazzi L, Franciolini F, Mora M, Catacuzzeno L, Pessia M. A Calsequestrin-1 Mutation Associated with a Skeletal Muscle Disease Alters Sarcoplasmic Ca2+ Release. PLoS One 2016; 11:e0155516. [PMID: 27196359 DOI: 10.1371/journal.pone.0155516] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 04/30/2016] [Indexed: 02/03/2023] Open
Abstract
An autosomal dominant protein aggregate myopathy, characterized by high plasma creatine kinase and calsequestrin-1 (CASQ1) accumulation in skeletal muscle, has been recently associated with a missense mutation in CASQ1 gene. The mutation replaces an evolutionarily-conserved aspartic acid with glycine at position 244 (p.D244G) of CASQ1, the main sarcoplasmic reticulum (SR) Ca2+ binding and storage protein localized at the terminal cisternae of skeletal muscle cells. Here, immunocytochemical analysis of myotubes, differentiated from muscle-derived primary myoblasts, shows that sarcoplasmic vacuolar aggregations positive for CASQ1 are significantly larger in CASQ1-mutated cells than control cells. A strong co-immuno staining of both RyR1 and CASQ1 was also noted in the vacuoles of myotubes and muscle biopsies derived from patients. Electrophysiological recordings and sarcoplasmic Ca2+ measurements provide evidence for less Ca2+ release from the SR of mutated myotubes when compared to that of controls. These findings further clarify the pathogenic nature of the p.D244G variant and point out defects in sarcoplasmic Ca2+ homeostasis as a mechanism underlying this human disease, which could be distinctly classified as “CASQ1-couplonopathy”.
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Wang XC, Wang S, Zhang M, Gao F, Yin C, Li H, Zhang Y, Hu SJ, Duan JH. Α-Dendrotoxin-sensitive Kv1 channels contribute to conduction failure of polymodal nociceptive C-fibers from rat coccygeal nerve. J Neurophysiol 2015; 115:947-57. [PMID: 26609114 DOI: 10.1152/jn.00786.2014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2014] [Accepted: 11/23/2015] [Indexed: 01/20/2023] Open
Abstract
It is known that some patients with diabetic neuropathy are usually accompanied by abnormal painful sensations. Evidence has accumulated that diabetic neuropathic pain is associated with the hyperexcitability of peripheral nociceptors. Previously, we demonstrated that reduced conduction failure of polymodal nociceptive C-fibers and enhanced voltage-dependent sodium currents of small dorsal root ganglion (DRG) neurons contribute to diabetic hyperalgesia. To further investigate whether and how potassium channels are involved in the conduction failure, α-dendrotoxin (α-DTX), a selective blocker of the low-threshold sustained Kv1 channel, was chosen to examine its functional capability in modulating the conduction properties of polymodal nociceptive C-fibers and the excitability of sensory neurons. We found that α-DTX reduced the conduction failure of C-fibers from coccygeal nerve in vivo accompanied by an increased initial conduction velocity but a decreased activity-dependent slowing of conduction velocity. In addition, the number of APs evoked by step currents was significantly enhanced after the treatment with α-DTX in small-diameter sensory neurons. Further study of the mechanism indicates α-DTX-sensitive K(+) current significantly reduced and the activation of this current in peak and steady state shifted to depolarization for diabetic neurons. Expression of Kv channel subunits Kv1.2 and Kv1.6 was downregulated in both small dorsal root ganglion neurons and peripheral C-fibers. Taken together, these results suggest that α-DTX-sensitive Kv1 channels might play an important role in regulating the conduction properties of polymodal nociceptive C-fibers and firing properties of sensory neurons.
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Affiliation(s)
- Xiu-Chao Wang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; Department of Psychology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Shan Wang
- State Key Laboratory of Cancer Biology, Department of Biochemistry and Molecular Biology, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ming Zhang
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Fang Gao
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Chun Yin
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Hao Li
- Team Nine, Brigade of Cadets, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Ying Zhang
- Department of Cardiovascular Surgery, Xijing Hospital, Xi'an, People's Republic of China; and
| | - San-Jue Hu
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China
| | - Jian-Hong Duan
- Institute of Neuroscience, Fourth Military Medical University, Xi'an, People's Republic of China; State Key Laboratory of Military Stomatology, School of Stomatology, Fourth Military Medical University, Xi'an, People's Republic of China
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15
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Saleeon W, Jansri U, Srikiatkhachorn A, Bongsebandhu-Phubhakdi S. The estrous cycle modulates voltage-gated ion channels in trigeminal ganglion neurons. J Physiol Sci 2015; 65:S29-S35. [PMID: 31941171 PMCID: PMC10722641 DOI: 10.1007/bf03405853] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Migraines typically occur more frequently in women than men because of the effects of estrogen on both the frequency and severity of migraine attacks. Many women suffer from migraine attacks during menstruation, which are known as menstrual migraines. The pathophysiology of menstrual migraines can be explored by using the rat estrous cycle, which shows a cyclical fluctuation of estrogen level that resembles the menstrual cycle. The aim of this study was to investigate whether different stages of the estrous cycle are involved in migraine development by comparing the excitability of trigeminal ganglion (TG) neurons in four different stages of the estrous cycle by using action potential (AP) parameter assessments. The stages of the estrous cycle were identified by a vaginal smear and measuring the estrogen levels in collected blood. The proestrus and estrus stages had higher estrogen levels compared with the diestrus and metestrus stages. Whole-cell patch clamp recordings demonstrated that TG neurons in the proestrus and estrus stage had lower AP threshold, lower rheobase, higher AP height, shorter AP falling time and deeper afterhyperpolarization (AHP) depth. Hence, our results revealed that the high level of estrogen in the proestrus and estrus stage alters the AP properties of TG neurons. Estrogen may increase membrane excitability and the summation of cellular responses, which alters the AP properties. The alterations of the AP properties in the proestrus and estrus stage may relate to a modification of voltage-gated ion channels in TG neurons, which is a pathogenesis for menstrual migraine. No COI.
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Affiliation(s)
- Wachirapong Saleeon
- Department of Physiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, Thailand
| | - Ukkrit Jansri
- Research Affairs, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, Thailand
| | - Anan Srikiatkhachorn
- Department of Physiology, Faculty of Medicine, Chulalongkorn University, 1873 Rama IV Road, Pathumwan, Bangkok, Thailand
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Galicia S, Cortes C, Cebada J, Méndez‐Balbuena I, Flores A. Firing properties of auditory primary afferents from the basilar papilla in the chick. Int J Dev Neurosci 2015; 44:92-101. [DOI: 10.1016/j.ijdevneu.2015.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Revised: 05/31/2015] [Accepted: 05/31/2015] [Indexed: 12/30/2022] Open
Affiliation(s)
- Salvador Galicia
- Escuela de BiologíaBenemérita Universidad Autónoma de Puebla (BUAP)Blvd. Valsequillo y Av. San Claudio, Edif. 112‐A C.U. Colonia Jardines de San ManuelCP72570Puebla, Pue.Mexico
| | - Celso Cortes
- Facultad de MedicinaBUAPAv. 13 Sur 2702 Colonia VolcanesCP72410Puebla, Pue.Mexico
| | - Jorge Cebada
- Facultad de MedicinaBUAPAv. 13 Sur 2702 Colonia VolcanesCP72410Puebla, Pue.Mexico
- Hospital Universitario de PueblaBUAPAv. 25 poniente 1301 Colonia VolcanesCP72410Puebla, Pue.Mexico
| | | | - Amira Flores
- Instituto de FisiologíaBUAPAv. 14 Sur 6301 Colonia Jardines de San ManuelCP72570Puebla, Pue.Mexico
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17
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Sforna L, D'Adamo MC, Servettini I, Guglielmi L, Pessia M, Franciolini F, Catacuzzeno L. Expression and function of a CP339,818-sensitive K⁺ current in a subpopulation of putative nociceptive neurons from adult mouse trigeminal ganglia. J Neurophysiol 2015; 113:2653-65. [PMID: 25652918 DOI: 10.1152/jn.00379.2014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 02/02/2015] [Indexed: 01/15/2023] Open
Abstract
Trigeminal ganglion (TG) neurons are functionally and morphologically heterogeneous, and the molecular basis of this heterogeneity is still not fully understood. Here we describe experiments showing that a subpopulation of neurons expresses a delayed-rectifying K(+) current (IDRK) with a characteristically high (nanomolar) sensitivity to the dihydroquinoline CP339,818 (CP). Although submicromolar CP has previously been shown to selectively block Kv1.3 and Kv1.4 channels, the CP-sensitive IDRK found in TG neurons could not be associated with either of these two K(+) channels. It could neither be associated with Kv2.1 channels homomeric or heteromerically associated with the Kv9.2, Kv9.3, or Kv6.4 subunits, whose block by CP, tested using two-electrode voltage-clamp recordings from Xenopus oocytes, resulted in the low micromolar range, nor to the Kv7 subfamily, given the lack of blocking efficacy of 3 μM XE991. Within the group of multiple-firing neurons considered in this study, the CP-sensitive IDRK was preferentially expressed in a subpopulation showing several nociceptive markers, such as small membrane capacitance, sensitivity to capsaicin, and slow afterhyperpolarization (AHP); in these neurons the CP-sensitive IDRK controls the membrane resting potential, the firing frequency, and the AHP duration. A biophysical study of the CP-sensitive IDRK indicated the presence of two kinetically distinct components: a fast deactivating component having a relatively depolarized steady-state inactivation (IDRKf) and a slow deactivating component with a more hyperpolarized V1/2 for steady-state inactivation (IDRKs).
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Affiliation(s)
- Luigi Sforna
- Dipartimento di Chimica, Biologia e Biotecnologie, Universitá di Perugia, Perugia, Italy; and
| | - Maria Cristina D'Adamo
- Dipartimento di Medicina Sperimentale, Facoltá di Medicina e Chirurgia, Universitá di Perugia, Perugia, Italy
| | - Ilenio Servettini
- Dipartimento di Medicina Sperimentale, Facoltá di Medicina e Chirurgia, Universitá di Perugia, Perugia, Italy
| | - Luca Guglielmi
- Dipartimento di Medicina Sperimentale, Facoltá di Medicina e Chirurgia, Universitá di Perugia, Perugia, Italy
| | - Mauro Pessia
- Dipartimento di Medicina Sperimentale, Facoltá di Medicina e Chirurgia, Universitá di Perugia, Perugia, Italy
| | - Fabio Franciolini
- Dipartimento di Chimica, Biologia e Biotecnologie, Universitá di Perugia, Perugia, Italy; and
| | - Luigi Catacuzzeno
- Dipartimento di Chimica, Biologia e Biotecnologie, Universitá di Perugia, Perugia, Italy; and
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Abstract
Neuropathic pain often fails to respond to conventional pain management procedures. here we review the aetiology of neuropathic pain as would result from peripheral neuropathy or injury. We show that inflammatory mediators released from damaged nerves and tissue are responsible for triggering ectopic activity in primary afferents and that this, in turn, provokes increased spinal cord activity and the development of ‘central sensitization’. Although evidence is mounting to support the role of interleukin-1β, prostaglandins and other cytokines in the onset of neuropathic pain, the clinical efficacy of drugs which antagonize or prevent the actions of these mediators is yet to be determined. basic science findings do, however, support the use of pre-emptive analgesia during procedures which involve nerve manipulation and the use of anti-inflammatory steroids as soon as possible following traumatic nerve injury.
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Honjoh T, Ji ZG, Yokoyama Y, Sumiyoshi A, Shibuya Y, Matsuzaka Y, Kawashima R, Mushiake H, Ishizuka T, Yawo H. Optogenetic patterning of whisker-barrel cortical system in transgenic rat expressing channelrhodopsin-2. PLoS One 2014; 9:e93706. [PMID: 24695456 DOI: 10.1371/journal.pone.0093706] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Accepted: 03/05/2014] [Indexed: 01/03/2023] Open
Abstract
The rodent whisker-barrel system has been an ideal model for studying somatosensory representations in the cortex. However, it remains a challenge to experimentally stimulate whiskers with a given pattern under spatiotemporal precision. Recently the optogenetic manipulation of neuronal activity has made possible the analysis of the neuronal network with precise spatiotemporal resolution. Here we identified the selective expression of channelrhodopsin-2 (ChR2), an algal light-driven cation channel, in the large mechanoreceptive neurons in the trigeminal ganglion (TG) as well as their peripheral nerve endings innervating the whisker follicles of a transgenic rat. The spatiotemporal pattern of whisker irradiation thus produced a barrel-cortical response with a specific spatiotemporal pattern as evidenced by electrophysiological and functional MRI (fMRI) studies. Our methods of generating an optogenetic tactile pattern (OTP) can be expected to facilitate studies on how the spatiotemporal pattern of touch is represented in the somatosensory cortex, as Hubel and Wiesel did in the visual cortex.
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20
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Hullugundi S, Ansuini A, Ferrari M, van den Maagdenberg A, Nistri A. A hyperexcitability phenotype in mouse trigeminal sensory neurons expressing the R192Q Cacna1a missense mutation of familial hemiplegic migraine type-1. Neuroscience 2014; 266:244-54. [DOI: 10.1016/j.neuroscience.2014.02.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Revised: 01/20/2014] [Accepted: 02/07/2014] [Indexed: 12/28/2022]
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Li N, Lu ZY, Yu LH, Burnstock G, Deng XM, Ma B. Inhibition of G protein-coupled P2Y2 receptor induced analgesia in a rat model of trigeminal neuropathic pain. Mol Pain 2014; 10:21. [PMID: 24642246 PMCID: PMC3995183 DOI: 10.1186/1744-8069-10-21] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Accepted: 03/04/2014] [Indexed: 01/29/2023] Open
Abstract
BACKGROUNDS ATP and P2X receptors play important roles in the modulation of trigeminal neuropathic pain, while the role of G protein-coupled P2Y₂ receptors and the underlying mechanisms are less clear. The threshold and frequency of action potentials, fast inactivating transient K+ channels (IA) are important regulators of membrane excitability in sensory neurons because of its vital role in the control of the spike onset. In this study, pain behavior tests, QT-RT-PCR, immunohistochemical staining, and patch-clamp recording, were used to investigate the role of P2Y₂ receptors in pain behaviour. RESULTS In control rats: 1) UTP, an agonist of P2Y₂/P2Y₄ receptors, caused a significant decrease in the mean threshold intensities for evoking action potentials and a striking increase in the mean number of spikes evoked by TG neurons. 2) UTP significantly inhibited IA and the expression of Kv1.4, Kv3.4 and Kv4.2 subunits in TG neurons, which could be reversed by the P2 receptor antagonist suramin and the ERK antagonist U0126. In ION-CCI (chronic constriction injury of infraorbital nerve) rats: 1) mRNA levels of Kv1.4, Kv3.4 and Kv4.2 subunits were significantly decreased, while the protein level of phosphorylated ERK was significantly increased. 2) When blocking P2Y₂ receptors by suramin or injection of P2Y2R antisense oligodeoxynucleotides both led to a time- and dose-dependent reverse of allodynia in ION-CCI rats. 3) Injection of P2Y₂ receptor antisense oligodeoxynucleotides induced a pronounced decrease in phosphorylated ERK expression and a significant increase in Kv1.4, Kv3.4 and Kv4.2 subunit expression in trigeminal ganglia. CONCLUSIONS Our data suggest that inhibition of P2Y₂ receptors leads to down-regulation of ERK-mediated phosphorylation and increase of the expression of I(A)-related Kv channels in trigeminal ganglion neurons, which might contribute to the clinical treatment of trigeminal neuropathic pain.
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Affiliation(s)
| | | | | | | | - Xiao-ming Deng
- Department of Physiology, The Key Laboratory of Molecular Neurobiology, Ministry of Education, Second Military Medical University, Shanghai 200433, P,R, China.
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22
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Catacuzzeno L, Sforna L, D'Adamo MC, Pessia M, Franciolini F. A method to identify tissue cell subpopulations with distinct multi-molecular profiles from data on co-localization of two markers at a time: the case of sensory ganglia. J Neurosci Methods 2014; 224:88-95. [PMID: 24412313 DOI: 10.1016/j.jneumeth.2013.12.015] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 11/23/2013] [Accepted: 12/31/2013] [Indexed: 01/03/2023]
Abstract
BACKGROUND Most biological tissues are characterized by high morphological and functional cell heterogeneity. To investigate this heterogeneity at the molecular level, scientists have tried to associate specific sets of molecular markers (molecular profiles) to functionally distinct cell subpopulations, evaluating their expression using immunochemistry and in situ hybridization techniques. NEW METHOD We propose here a novel analysis that allows the estimation of the frequency of cells expressing distinct molecular profiles starting from data on the co-expression of two markers at a time. In order to facilitate the application of the proposed analysis, we developed and make available a user-friendly window-based software. RESULTS We successfully applied the analytical method to experimental data from adult rat sensory neurons. In a first application we subgrouped DRG neurons in 11 subpopulations on the basis of the co-expression of 6 molecular markers (the TRPs type V1, A1, and M8 and the trks type A, B, and C). In a second application we found that while rat DRG have significant frequencies of peptidergic/IB4-negative and non-peptidergic/IB4-positive nociceptors, rat TG neurons lack almost completely these two subpopulations. COMPARISON WITH EXISTING METHODS The analytical method here proposed overcomes the limitations of the presently available experimental techniques, most of which can assess the co-expression of only few molecular markers at a time. CONCLUSIONS This new method will allow a better understanding of the molecular and cellular heterogeneity of tissues in normal and pathological conditions.
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Affiliation(s)
- Lugi Catacuzzeno
- Dipartimento di Chimica, Biologia e Biotecnologie, Universita' di Perugia, via Pascoli 1, Perugia, Italy.
| | - Luigi Sforna
- Dipartimento di Chimica, Biologia e Biotecnologie, Universita' di Perugia, via Pascoli 1, Perugia, Italy
| | - Maria Cristina D'Adamo
- Dipartimento di Medicina Sperimentale, Sezione di Fisiologia e Biochimica, Universita' di Perugia, Perugia, Italy
| | - Mauro Pessia
- Dipartimento di Medicina Sperimentale, Sezione di Fisiologia e Biochimica, Universita' di Perugia, Perugia, Italy
| | - Fabio Franciolini
- Dipartimento di Chimica, Biologia e Biotecnologie, Universita' di Perugia, via Pascoli 1, Perugia, Italy
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Watanabe T, Shimazaki T, Mishiro A, Suzuki T, Hirata H, Tanimoto M, Oda Y. Coexpression of auxiliary Kvβ2 subunits with Kv1.1 channels is required for developmental acquisition of unique firing properties of zebrafish Mauthner cells. J Neurophysiol 2013; 111:1153-64. [PMID: 24335214 DOI: 10.1152/jn.00596.2013] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Each neuron possesses a unique firing property, which is largely attributed to heterogeneity in the composition of voltage-gated ion channel complexes. Zebrafish Mauthner (M) cells, which are bilaterally paired giant reticulospinal neurons (RSNs) in the hindbrain and induce rapid escape behavior, generate only a single spike at the onset of depolarization. This single spiking is in contrast with the repetitive firing of the M cell's morphologically homologous RSNs, MiD2cm and MiD3cm, which are also involved in escapes. However, how the unique firing property of M cells is established and the underlying molecular mechanisms remain unclear. In the present study, we first demonstrated that the single-spiking property of M cells was acquired at 4 days postfertilization (dpf), accompanied by an increase in dendrotoxin I (DTX)-sensitive low-threshold K(+) currents, prior to which the M cell repetitively fires as its homologs. Second, in situ hybridization showed that among DTX-sensitive Kv1 channel α-subunits, zKv1.1a was unexpectedly expressed even in the homologs and the bursting M cells at 2 dpf. In contrast, zKvβ2b, an auxiliary β-subunit of Kv1 channels, was expressed only in the single-spiking M cells. Third, zKv1.1a expressed in Xenopus oocytes functioned as a low-threshold K(+) channel, and its currents were enhanced by coexpression of zKvβ2b subunits. Finally, knockdown of zKvβ2b expression in zebrafish larvae resulted in repetitive firing of M cells at 4 dpf. Taken together, these results suggest that associative expression of Kvβ2 subunits with Kv1.1 channels is crucial for developmental acquisition of the unique firing properties of the M cells among homologous neurons.
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Affiliation(s)
- Takaki Watanabe
- Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan; and
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Tsantoulas C, Zhu L, Yip P, Grist J, Michael GJ, McMahon SB. Kv2 dysfunction after peripheral axotomy enhances sensory neuron responsiveness to sustained input. Exp Neurol 2014; 251:115-26. [PMID: 24252178 DOI: 10.1016/j.expneurol.2013.11.011] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/21/2013] [Accepted: 11/07/2013] [Indexed: 12/16/2022]
Abstract
Peripheral nerve injuries caused by trauma are associated with increased sensory neuron excitability and debilitating chronic pain symptoms. Axotomy-induced alterations in the function of ion channels are thought to largely underlie the pathophysiology of these phenotypes. Here, we characterise the mRNA distribution of Kv2 family members in rat dorsal root ganglia (DRG) and describe a link between Kv2 function and modulation of sensory neuron excitability. Kv2.1 and Kv2.2 were amply expressed in cells of all sizes, being particularly abundant in medium-large neurons also immunoreactive for neurofilament-200. Peripheral axotomy led to a rapid, robust and long-lasting transcriptional Kv2 downregulation in the DRG, correlated with the onset of mechanical and thermal hypersensitivity. The consequences of Kv2 loss-of-function were subsequently investigated in myelinated neurons using intracellular recordings on ex vivo DRG preparations. In naïve neurons, pharmacological Kv2.1/Kv2.2 inhibition by stromatoxin-1 (ScTx) resulted in shortening of action potential (AP) after-hyperpolarization (AHP). In contrast, ScTx application on axotomized neurons did not alter AHP duration, consistent with the injury-induced Kv2 downregulation. In accordance with a shortened AHP, ScTx treatment also reduced the refractory period and improved AP conduction to the cell soma during high frequency stimulation. These results suggest that Kv2 downregulation following traumatic nerve lesion facilitates greater fidelity of repetitive firing during prolonged input and thus normal Kv2 function is postulated to limit neuronal excitability. In summary, we have profiled Kv2 expression in sensory neurons and provide evidence for the contribution of Kv2 dysfunction in the generation of hyperexcitable phenotypes encountered in chronic pain states. Kv2.1 and Kv2.2 are expressed in rat dorsal root ganglion neurons. Kv2 subunits are most abundant in myelinated sensory neurons. Kv2.1 and Kv.2 subunits are downregulated in a traumatic nerve injury pain model. Kv2 inhibition ex vivo allows higher firing rates during sustained stimulation. We conclude that Kv2 channels contribute to limiting peripheral neuron excitability.
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Tel’ka MV, Rykhal’skii OV, Veselovskii NS. Electrophysiological Properties of Cultured Neurons of the Rat Trigeminal Ganglion. NEUROPHYSIOLOGY+ 2013. [DOI: 10.1007/s11062-013-9340-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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26
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Abstract
Neuron firing patterns underpin the detection and processing of stimuli, influence synaptic interactions, and contribute to the function of networks. To understand how intrinsic membrane properties determine firing patterns, we investigated the biophysical basis of single and repetitive firing in spinal neurons of hatchling Xenopus laevis tadpoles, a well-understood vertebrate model; experiments were conducted in situ. Primary sensory Rohon-Beard (RB) neurons fire singly in response to depolarising current, and dorsolateral (DL) interneurons fire repetitively. RB neurons exhibited a large tetrodotoxin-sensitive sodium current; in DL neurons, the sodium current density was significantly lower. High-voltage-activated calcium currents were similar in both neuron types. There was no evidence of persistent sodium currents, low-voltage-activated calcium currents, or hyperpolarisation-activated currents. In RB neurons, the potassium current was dominated by a tetraethylammonium-sensitive slow component (I(Ks) ); a fast component (I(Kf) ), sensitive to 4-aminopyridine, predominated in DL neurons. Sequential current-clamp and voltage-clamp recordings in individual neurons suggest that high densities of I(Ks) prevent repetitive firing; where I(Ks) is small, I(Kf) density determines the frequency of repetitive firing. Intermediate densities of I(Ks) and I(Kf) allow neurons to fire a few additional spikes on strong depolarisation; this property typifies a novel subset of RB neurons, and may activate escape responses. We discuss how this ensemble of currents and firing patterns underpins the operation of the Xenopus locomotor network, and suggest how simple mechanisms might underlie the similar firing patterns seen in the neurons of diverse species.
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27
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Sun W, Miao B, Wang XC, Duan JH, Ye X, Han WJ, Wang WT, Luo C, Hu SJ. Gastrodin inhibits allodynia and hyperalgesia in painful diabetic neuropathy rats by decreasing excitability of nociceptive primary sensory neurons. PLoS One 2012; 7:e39647. [PMID: 22761855 PMCID: PMC3382466 DOI: 10.1371/journal.pone.0039647] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 05/24/2012] [Indexed: 01/29/2023] Open
Abstract
Painful diabetic neuropathy (PDN) is a common complication of diabetes mellitus and adversely affects the patients' quality of life. Evidence has accumulated that PDN is associated with hyperexcitability of peripheral nociceptive primary sensory neurons. However, the precise cellular mechanism underlying PDN remains elusive. This may result in the lacking of effective therapies for the treatment of PDN. The phenolic glucoside, gastrodin, which is a main constituent of the Chinese herbal medicine Gastrodia elata Blume, has been widely used as an anticonvulsant, sedative, and analgesic since ancient times. However, the cellular mechanisms underlying its analgesic actions are not well understood. By utilizing a combination of behavioral surveys and electrophysiological recordings, the present study investigated the role of gastrodin in an experimental rat model of STZ-induced PDN and to further explore the underlying cellular mechanisms. Intraperitoneal administration of gastrodin effectively attenuated both the mechanical allodynia and thermal hyperalgesia induced by STZ injection. Whole-cell patch clamp recordings were obtained from nociceptive, capsaicin-sensitive small diameter neurons of the intact dorsal root ganglion (DRG). Recordings from diabetic rats revealed that the abnormal hyperexcitability of neurons was greatly abolished by application of GAS. To determine which currents were involved in the antinociceptive action of gastrodin, we examined the effects of gastrodin on transient sodium currents (I(NaT)) and potassium currents in diabetic small DRG neurons. Diabetes caused a prominent enhancement of I(NaT) and a decrease of potassium currents, especially slowly inactivating potassium currents (I(AS)); these effects were completely reversed by GAS in a dose-dependent manner. Furthermore, changes in activation and inactivation kinetics of I(NaT) and total potassium current as well as I(AS) currents induced by STZ were normalized by GAS. This study provides a clear cellular basis for the peripheral analgesic action of gastrodin for the treatment of chronic pain, including PDN.
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Affiliation(s)
- Wei Sun
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
- Institute for Biomedical Sciences of Pain and Institute for Functional Brain Disorders, Tangdu Hospital, the Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Bei Miao
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
- Jiangsu Province Key Laboratory of Anesthesiology and Center for Pain Research and Treatment, Xuzhou Medical College, Xuzhou, People’s Republic of China
| | - Xiu-Chao Wang
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Jian-Hong Duan
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Xin Ye
- Department of Endocrinology, The 451th Hospital of People’s Liberation Army, Xi’an, People’s Republic of China
| | - Wen-Juan Han
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Wen-Ting Wang
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - Ceng Luo
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
| | - San-Jue Hu
- Institute of Neuroscience, The Fourth Military Medical University, Xi’an, People’s Republic of China
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Tao J, Liu P, Xiao Z, Zhao H, Gerber BR, Cao YQ. Effects of familial hemiplegic migraine type 1 mutation T666M on voltage-gated calcium channel activities in trigeminal ganglion neurons. J Neurophysiol 2011; 107:1666-80. [PMID: 22190617 DOI: 10.1152/jn.00551.2011] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Familial hemiplegic migraine type 1 (FHM-1), a rare hereditary form of migraine with aura and hemiparesis, serves as a good model for exploring migraine pathophysiology. The FHM-1 gene encodes the pore-forming Ca(V)2.1 subunit of human P/Q-type voltage-gated Ca(2+) channels (VGCCs). Some FHM-1 mutations result in a decrease of whole cell P/Q-type current density in transfected cells/neurons. Questions remain as to whether and how these mutations may increase the gain of the trigeminal nociceptive pathway underlying migraine headache. Here, we investigated the effects of T666M, the most frequently occurring FHM-1 mutation, on VGCC currents and neuronal excitability in trigeminal ganglion (TG) neurons. We expressed human wild-type and T666M Ca(V)2.1 subunits in cultured TG neurons from Ca(V)2.1 knockout mice and recorded whole cell VGCC currents in transfected neurons. Currents mediated by individual VGCC subtypes were dissected according to their pharmacological and biophysical properties. TG neurons were sorted into three subpopulations based on their soma size and their affinity to isolectin B4 (IB4). We found that the T666M mutation did not affect total or surface expression of Ca(V)2.1 proteins but caused a profound reduction of P/Q-type current in all subtypes of TG neurons. Interestingly, a compensatory increase in Ca(V)3.2-mediated low-voltage-activated T-type currents only occurred in small IB4-negative (IB4(-)) TG neurons expressing T666M subunits. Current-clamp recordings showed that the T666M mutation resulted in hyperexcitability of the small IB4(-) TG population. Taken together, our results suggest a possible scenario through which FHM-1 mutations might increase the gain of the trigeminal nociceptive pathway.
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Affiliation(s)
- Jin Tao
- Washington University Pain Center and Department of Anesthesiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Fioretti B, Catacuzzeno L, Sforna L, Gerke-Duncan MB, van den Maagdenberg AMJM, Franciolini F, Connor M, Pietrobon D. Trigeminal ganglion neuron subtype-specific alterations of Ca(V)2.1 calcium current and excitability in a Cacna1a mouse model of migraine. J Physiol 2011; 589:5879-95. [PMID: 22005682 DOI: 10.1113/jphysiol.2011.220533] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Familial hemiplegic migraine type-1 (FHM1), a monogenic subtype of migraine with aura, is caused by gain-of-function mutations in Ca(V)2.1 (P/Q-type) calcium channels. The consequences of FHM1 mutations on the trigeminovascular pathway that generates migraine headache remain largely unexplored. Here we studied the calcium currents and excitability properties of two subpopulations of small-diameter trigeminal ganglion (TG) neurons from adult wild-type (WT) and R192Q FHM1 knockin (KI) mice: capsaicin-sensitive neurons without T-type calcium currents (CS) and capsaicin-insensitive neurons characterized by the expression of T-type calcium currents (CI-T). Small TG neurons retrogradely labelled from the dura are mostly CS neurons, while CI-T neurons were not present in the labelled population. CS and CI-T neurons express Ca(V)2.1 channels with different activation properties, and the Ca(V)2.1 channels are differently affected by the FHM1 mutation in the two TG neuron subtypes. In CI-T neurons from FHM1 KI mice there was a larger P/Q-type current density following mild depolarizations, a larger action potential (AP)-evoked calcium current and a longer AP duration when compared to CI-T neurons from WT mice. In striking contrast, the P/Q-type current density, voltage dependence and kinetics were not altered by the FHM1 mutation in CS neurons. The excitability properties of mutant CS neurons were also unaltered. Congruently, the FHM1 mutation did not alter depolarization-evoked CGRP release from the dura mater, while CGRP release from the trigeminal ganglion was larger in KI compared to WT mice. Our findings suggest that the facilitation of peripheral mechanisms of CGRP action, such as dural vasodilatation and nociceptor sensitization at the meninges, does not contribute to the generation of headache in FHM1.
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Affiliation(s)
- B Fioretti
- Department of Biomedical Sciences, University of Padova and CNR Institute of Neuroscience, 35121 Padova, Italy
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Cho HJ, Furness JB, Jennings EA. Postnatal maturation of the hyperpolarization-activated cation current, I(h), in trigeminal sensory neurons. J Neurophysiol 2011; 106:2045-56. [PMID: 21753027 DOI: 10.1152/jn.00798.2010] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Hyperpolarization-activated inward currents (I(h)) contribute to neuronal excitability in sensory neurons. Four subtypes of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels generate I(h), with different activation kinetics and cAMP sensitivities. The aim of the present study was to examine the postnatal development of I(h) and HCN channel subunits in trigeminal ganglion (TG) neurons. I(h) was investigated in acutely dissociated TG neurons from rats aged between postnatal day (P)1 and P35 with whole cell patch-clamp electrophysiology. In voltage-clamp studies, I(h) was activated by a series of hyperpolarizing voltage steps from -40 mV to -120 mV in -10-mV increments. Tail currents from a common voltage step (-100 mV) were used to determine I(h) voltage dependence. I(h) activation was faster in older rats and occurred at more depolarized potentials; the half-maximal activation voltage (V(1/2)) changed from -89.4 mV (P1) to -81.6 mV (P35). In current-clamp studies, blocking I(h) with ZD7288 caused membrane hyperpolarization and increases in action potential half-duration at all postnatal ages examined. ZD7288 also reduced the action potential firing frequency in multiple-firing neurons. Western blot analysis of the TG detected immunoreactive bands corresponding to all HCN subtypes. HCN1 and HCN2 band density increased with postnatal age, whereas the low-intensity HCN3 and moderate-intensity HCN4 bands were not changed. This study suggests that functional I(h) are activated in rat trigeminal sensory neurons from P1 during postnatal development, have an increasing role with age, and modify neuronal excitability.
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Affiliation(s)
- Hyun-Jung Cho
- Anatomy and Cell Biology, University of Melbourne, Parkville, Victoria, Australia
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Winlove CIP, Roberts A. Pharmacology of currents underlying the different firing patterns of spinal sensory neurons and interneurons identified in vivo using multivariate analysis. J Neurophysiol 2011; 105:2487-500. [PMID: 21346204 DOI: 10.1152/jn.00779.2010] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The operation of neuronal networks depends on the firing patterns of the network's neurons. When sustained current is injected, some neurons in the central nervous system fire a single action potential and others fire repetitively. For example, in Xenopus laevis tadpoles, primary-sensory Rohon-Beard (RB) neurons fired a single action potential in response to 300-ms rheobase current injections, whereas dorsolateral (DL) interneurons fired repetitively at 10-20 Hz. To investigate the basis for these differences in vivo, we examined drug-induced changes in the firing patterns of Xenopus spinal neurons using whole cell current-clamp recordings. Neuron types were initially separated through cluster analysis, and we compared results produced using different clustering algorithms. We used these results to develop a predictive function to classify subsequently recorded neurons. The potassium channel blocker tetraethylammonium (TEA) converted single-firing RB neurons to low-frequency repetitive firing but reduced the firing frequency of repetitive-firing DL interneurons. Firing frequency in DL interneurons was also reduced by the potassium channel blockers 4-aminopyridine (4-AP), catechol, and margatoxin; 4-AP had the greatest effect. The calcium channel blockers amiloride and nimodipine had few effects on firing in either neuron type but reduced action potential duration in DL interneurons. Muscarine, which blocks M-currents, did not affect RB neurons but reduced firing frequency in DL interneurons. These results suggest that potassium currents may control neuron firing patterns: a TEA-sensitive current prevents repetitive firing in RB neurons, whereas a 4-AP-sensitive current underlies repetitive firing in DL interneurons. The cluster and discriminant analysis described could help to classify neurons in other systems.
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Affiliation(s)
- Crawford I P Winlove
- Neurobiology, School of Biological Sciences, Woodland Road, Bristol BS8 2UG, United Kingdom.
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Abstract
In the companion paper we show that GAD67-GFP+ (GFP+) inhibitory neurons located in the Nucleus of Roller of the mouse brain stem can be classified into two main groups (tonic and phasic) based on their firing patterns in responses to injected depolarizing current steps. In this study we examined the responses of GFP+ cells to fluctuating sinusoidal ("chirp") current stimuli. Membrane impedance profiles in response to chirp stimulation showed that nearly all phasic cells exhibited subthreshold resonance, whereas the majority of tonic GFP+ cells were nonresonant. In general, subthreshold resonance was associated with a relatively fast passive membrane time constant and low input resistance. In response to suprathreshold chirp current stimulation at a holding potential just below spike threshold the majority of tonic GFP+ cells fired multiple action potentials per cycle at low input frequencies (<5 Hz) and either stopped firing or were not entrained by the chirp at higher input frequencies (= tonic low-pass cells). A smaller group of phasic GFP+ cells did not fire at low input frequency but were able to phase-lock 1:1 at intermediate chirp frequencies (= band-pass cells). Spike timing reliability was tested with repeated chirp stimuli and our results show that phasic cells were able to reliably fire when they phase-locked 1:1 over a relatively broad range of input frequencies. Most tonic low-pass cells showed low reliability and poor phase-locking ability. Computer modeling suggested that these different firing resonance properties among GFP+ cells are due to differences in passive and active membrane properties and spiking mechanisms. This heterogeneity of resonance properties might serve to selectively activate subgroups of interneurons.
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Affiliation(s)
- J F M van Brederode
- Department of Physiology and Biophysics, University of Washington, 1705 NE Pacific St., HSB G424, Box 357290, Seattle, WA 98195-7290, USA.
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Tong M, Hernandez JL, Purcell EK, Altschuler RA, Duncan RK. The intrinsic electrophysiological properties of neurons derived from mouse embryonic stem cells overexpressing neurogenin-1. Am J Physiol Cell Physiol 2010; 299:C1335-44. [PMID: 20861468 DOI: 10.1152/ajpcell.00207.2010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
A mouse embryonic stem (ES) cell line containing an inducible transgene for the proneural gene Neurog1 has been used to generate glutamatergic neurons at a high efficiency. The present study used in vitro electrophysiology to establish the timeline for acquiring a functional neuronal phenotype in Neurog1-induced cells exhibiting a neuronal morphology. TTX-sensitive action potentials could be evoked from over 80% of the cells after only 4.5 days in vitro (DIV). These cells uniformly showed rapidly adapting responses to current injection, firing one to three action potentials at the onset of the stimulus. In the absence of Neurog1, a limited number of ES cells adopted a neuronal morphology, but these cells displayed slow calcium depolarizations rather than sodium-based spikes. Voltage-gated Na(+), K(+), and Ca(2+) currents were present in nearly all induced cells as early as 4.5 DIV. The voltage-dependent properties of these currents changed little from 4 to 12 DIV with half-activation voltage varying by <10 mV for any current type throughout the culture period. This study demonstrates that forced expression of proneural genes can induce ES cells to quickly acquire a functional neuronal phenotype with mature electrophysiological properties. Transient overexpression of Neurog1 may be used in neural repair strategies that require the rapid induction of functional neurons from pluripotent stem cells.
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Affiliation(s)
- Mingjie Tong
- Kresge Hearing Research Institute, University of Michigan, Ann Arbor, Michigan 48109-5616, USA
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Cao XH, Byun HS, Chen SR, Cai YQ, Pan HL. Reduction in voltage-gated K+ channel activity in primary sensory neurons in painful diabetic neuropathy: role of brain-derived neurotrophic factor. J Neurochem 2010; 114:1460-75. [PMID: 20557422 DOI: 10.1111/j.1471-4159.2010.06863.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Abnormal hyperexcitability of primary sensory neurons plays an important role in neuropathic pain. Voltage-gated potassium (Kv) channels regulate neuronal excitability by affecting the resting membrane potential and influencing the repolarization and frequency of the action potential. In this study, we determined changes in Kv channels in dorsal root ganglion (DRG) neurons in a rat model of diabetic neuropathic pain. The densities of total Kv, A-type (IA) and sustained delayed (IK) currents were markedly reduced in medium- and large-, but not in small-, diameter DRG neurons in diabetic rats. Quantitative RT-PCR analysis revealed that the mRNA levels of IA subunits, including Kv1.4, Kv3.4, Kv4.2, and Kv4.3, in the DRG were reduced approximately 50% in diabetic rats compared with those in control rats. However, there were no significant differences in the mRNA levels of IK subunits (Kv1.1, Kv1.2, Kv2.1, and Kv2.2) in the DRG between the two groups. Incubation with brain-derived neurotrophic factor (BDNF) caused a large reduction in Kv currents, especially IA currents, in medium and large DRG neurons from control rats. Furthermore, the reductions in Kv currents and mRNA levels of IA subunits in diabetic rats were normalized by pre-treatment with anti-BDNF antibody or K252a, a TrkB tyrosine kinase inhibitor. In addition, the number of medium and large DRG neurons with BDNF immunoreactivity was greater in diabetic than control rats. Collectively, our findings suggest that diabetes primarily reduces Kv channel activity in medium and large DRG neurons. Increased BDNF activity in these neurons likely contributes to the reduction in Kv channel function through TrkB receptor stimulation in painful diabetic neuropathy.
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Affiliation(s)
- Xue-Hong Cao
- Department of Anesthesiology and Perioperative Medicine, The University of Texas MD Anderson Cancer Center, Houston, Texas 77030, USA
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Wu ZZ, Li DP, Chen SR, Pan HL. Aminopyridines potentiate synaptic and neuromuscular transmission by targeting the voltage-activated calcium channel beta subunit. J Biol Chem 2009; 284:36453-36461. [PMID: 19850918 DOI: 10.1074/jbc.m109.075523] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Aminopyridines such as 4-aminopyridine (4-AP) are widely used as voltage-activated K(+) (Kv) channel blockers and can improve neuromuscular function in patients with spinal cord injury, myasthenia gravis, or multiple sclerosis. Here, we present novel evidence that 4-AP and several of its analogs directly stimulate high voltage-activated Ca(2+) channels (HVACCs) in acutely dissociated neurons. 4-AP, 4-(aminomethyl)pyridine, 4-(methylamino)pyridine, and 4-di(methylamino)pyridine profoundly increased HVACC, but not T-type, currents in dissociated neurons from the rat dorsal root ganglion, superior cervical ganglion, and hippocampus. The widely used Kv channel blockers, including tetraethylammonium, alpha-dendrotoxin, phrixotoxin-2, and BDS-I, did not mimic or alter the effect of 4-AP on HVACCs. In HEK293 cells expressing various combinations of N-type (Cav2.2) channel subunits, 4-AP potentiated Ca(2+) currents primarily through the intracellular beta(3) subunit. In contrast, 4-AP had no effect on Cav3.2 channels expressed in HEK293 cells. Furthermore, blocking Kv channels did not mimic or change the potentiating effects of 4-AP on neurotransmitter release from sensory and motor nerve terminals. Thus, our findings challenge the conventional view that 4-AP facilitates synaptic and neuromuscular transmission by blocking Kv channels. Aminopyridines can directly target presynaptic HVACCs to potentiate neurotransmitter release independent of Kv channels.
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Affiliation(s)
- Zi-Zhen Wu
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - De-Pei Li
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Shao-Rui Chen
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
| | - Hui-Lin Pan
- Division of Anesthesiology and Critical Care, The University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030; Program in Neuroscience, The University of Texas Graduate School of Biomedical Sciences, Houston, Texas 77225.
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Feng B, Strichartz G. Endothelin-1 raises excitability and reduces potassium currents in sensory neurons. Brain Res Bull 2009; 79:345-50. [PMID: 19409452 PMCID: PMC2703700 DOI: 10.1016/j.brainresbull.2009.04.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2008] [Revised: 03/29/2009] [Accepted: 04/23/2009] [Indexed: 01/08/2023]
Abstract
Exposure to endothelin-1 (ET-1, 50 nM) of sensory neurons, acutely isolated from rat dorsal root ganglia (DRG), results in an increase in the number of action potentials elicited by a linear ramp of stimulating current. The changes are complete in 5 min after ET-1 treatment and do not reverse in 5-10 min after ET-1's removal. Neither the resting potential, nor the threshold potential for the first or second action potentials, nor their rate-of-rise or decay, are changed by ET-1 exposure, but the slow depolarizations which occur before the first and second action potentials during the current ramp are increased by ca. 50% by ET-1. The delayed rectifier type of K(+) currents (I(K)), measured under whole-cell voltage clamp, are depressed by approximately 30% during such exposure to ET-1. The voltage-dependent gating of steady-state I(K) and the current kinetics are unchanged by ET-1, leaving the sole effect as a drop in the number of available channels. I(K) is affected by ET-1 only in Isolectin B(4)-positive cells, suggesting that there may be a selective action in enhancing impulse activity on this class of nociceptive neuron. This decrease in I(K) will potentiate the excitability-inducing actions of the previously reported negative shift in tetrodotoxin-resistant Na(+) channel gating in such neurons.
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Affiliation(s)
- Bihua Feng
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, MA 02115, USA
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Affiliation(s)
- Felix Viana
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, San Juan de Alicante, 03550, Spain. @umh.es
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