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Lucas-Romero J, Rivera-Arconada I, Lopez-Garcia JA. Noise or signal? Spontaneous activity of dorsal horn neurons: patterns and function in health and disease. Pflugers Arch 2024; 476:1171-1186. [PMID: 38822875 PMCID: PMC11271371 DOI: 10.1007/s00424-024-02971-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2023] [Revised: 04/10/2024] [Accepted: 05/05/2024] [Indexed: 06/03/2024]
Abstract
Spontaneous activity refers to the firing of action potentials by neurons in the absence of external stimulation. Initially considered an artifact or "noise" in the nervous system, it is now recognized as a potential feature of neural function. Spontaneous activity has been observed in various brain areas, in experimental preparations from different animal species, and in live animals and humans using non-invasive imaging techniques. In this review, we specifically focus on the spontaneous activity of dorsal horn neurons of the spinal cord. We use a historical perspective to set the basis for a novel classification of the different patterns of spontaneous activity exhibited by dorsal horn neurons. Then we examine the origins of this activity and propose a model circuit to explain how the activity is generated and transmitted to the dorsal horn. Finally, we discuss possible roles of this activity during development and during signal processing under physiological conditions and pain states. By analyzing recent studies on the spontaneous activity of dorsal horn neurons, we aim to shed light on its significance in sensory processing. Understanding the different patterns of activity, the origins of this activity, and the potential roles it may play, will contribute to our knowledge of sensory mechanisms, including pain, to facilitate the modeling of spinal circuits and hopefully to explore novel strategies for pain treatment.
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Affiliation(s)
- Javier Lucas-Romero
- Department of Systems Biology, University of Alcala, 28805, Madrid, Spain
- Department of Physical Therapy, Washington University School of Medicine, Washington University in St. Louis, St. Louis, MO, 63108, USA
| | | | - Jose Antonio Lopez-Garcia
- Department of Systems Biology, University of Alcala, 28805, Madrid, Spain.
- Departamento de Biologia de Sistemas, Edificio de Medicina, Universidad de Alcala, Ctra. Madrid-Barcelona, Km 33,600, 28805, Alcala de Henares, Madrid, Spain.
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Lucas-Romero J, Rivera-Arconada I, Lopez-Garcia JA. Synchronous firing of dorsal horn neurons at the origin of dorsal root reflexes in naïve and paw-inflamed mice. Front Cell Neurosci 2022; 16:1004956. [PMID: 36212688 PMCID: PMC9539274 DOI: 10.3389/fncel.2022.1004956] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 09/05/2022] [Indexed: 12/05/2022] Open
Abstract
Spinal interneurons located in the dorsal horn induce primary afferent depolarization (PAD) controlling the excitability of the afferent’s terminals. Following inflammation, PAD may reach firing threshold contributing to maintain inflammation and pain. Our aim was to study the collective behavior of dorsal horn neurons, its relation to backfiring of primary afferents and the effects of a peripheral inflammation in this system. Experiments were performed on slices of spinal cord obtained from naïve adult mice or mice that had suffered an inflammatory pretreatment. Simultaneous recordings from groups of dorsal horn neurons and primary afferents were obtained and machine-learning methodology was used to analyze effective connectivity between them. Dorsal horn recordings showed grouping of spontaneous action potentials from different neurons in “population bursts.” These occurred at irregular intervals and were formed by action potentials from all classes of neurons recorded. Compared to naïve, population bursts from treated animals concentrated more action potentials, had a faster onset and a slower decay. Population bursts were disrupted by perfusion of picrotoxin and held a strong temporal correlation with backfiring of afferents. Effective connectivity analysis allowed pinpointing specific neurons holding pre- or post-synaptic relation to the afferents. Many of these neurons had an irregular fast bursting pattern of spontaneous firing. We conclude that population bursts contain action potentials from neurons presynaptic to the afferents which are likely to control their excitability. Peripheral inflammation may enhance synchrony in these neurons, increasing the chance of triggering action potentials in primary afferents and contributing toward central sensitization.
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Zhu M, Yan Y, Cao X, Zeng F, Xu G, Shen W, Li F, Luo L, Wang Z, Zhang Y, Zhang X, Zhang D, Liu T. Electrophysiological and Morphological Features of Rebound Depolarization Characterized Interneurons in Rat Superficial Spinal Dorsal Horn. Front Cell Neurosci 2021; 15:736879. [PMID: 34621158 PMCID: PMC8490703 DOI: 10.3389/fncel.2021.736879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 08/25/2021] [Indexed: 11/18/2022] Open
Abstract
Substantia gelatinosa (SG) neurons, which are located in the spinal dorsal horn (lamina II), have been identified as the “central gate” for the transmission and modulation of nociceptive information. Rebound depolarization (RD), a biophysical property mediated by membrane hyperpolarization that is frequently recorded in the central nervous system, contributes to shaping neuronal intrinsic excitability and, in turn, contributes to neuronal output and network function. However, the electrophysiological and morphological properties of SG neurons exhibiting RD remain unclarified. In this study, whole-cell patch-clamp recordings were performed on SG neurons from parasagittal spinal cord slices. RD was detected in 44.44% (84 out of 189) of the SG neurons recorded. We found that RD-expressing neurons had more depolarized resting membrane potentials, more hyperpolarized action potential (AP) thresholds, higher AP amplitudes, shorter AP durations, and higher spike frequencies in response to depolarizing current injection than neurons without RD. Based on their firing patterns and morphological characteristics, we propose that most of the SG neurons with RD mainly displayed tonic firing (69.05%) and corresponded to islet cell morphology (58.82%). Meanwhile, subthreshold currents, including the hyperpolarization-activated cation current (Ih) and T-type calcium current (IT), were identified in SG neurons with RD. Blockage of Ih delayed the onset of the first spike in RD, while abolishment of IT significantly blunted the amplitude of RD. Regarding synaptic inputs, SG neurons with RD showed lower frequencies in both spontaneous and miniature excitatory synaptic currents. Furthermore, RD-expressing neurons received either Aδ- or C-afferent-mediated monosynaptic and polysynaptic inputs. However, RD-lacking neurons received afferents from monosynaptic and polysynaptic Aδ fibers and predominantly polysynaptic C-fibers. These findings demonstrate that SG neurons with RD have a specific cell-type distribution, and may differentially process somatosensory information compared to those without RD.
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Affiliation(s)
- Mengye Zhu
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Yi Yan
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Xuezhong Cao
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Fei Zeng
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Gang Xu
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Wei Shen
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Fan Li
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Lingyun Luo
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Zhijian Wang
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Yong Zhang
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Xuexue Zhang
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Daying Zhang
- Department of Pain Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China.,Institute of Pain Medicine, Jiangxi Academy of Clinical and Medical Sciences, Nanchang, China
| | - Tao Liu
- Center for Experimental Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, China
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Tadros MA, Zouikr I, Hodgson DM, Callister RJ. Excitability of Rat Superficial Dorsal Horn Neurons Following a Neonatal Immune Challenge. Front Neurol 2018; 9:743. [PMID: 30245664 PMCID: PMC6137193 DOI: 10.3389/fneur.2018.00743] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Accepted: 08/17/2018] [Indexed: 12/15/2022] Open
Abstract
Previous studies have shown that neonatal exposure to a mild inflammatory challenge, such as lipopolysaccharide (LPS, Salmonella enteriditis) results in altered pain behaviors later in life. To further characterize the impact of a neonatal immune challenge on pain processing, we examined the excitability of superficial dorsal horn (SDH) neurons following neonatal LPS exposure and subsequent responses to noxious stimulation at three time-points during early postnatal development. Wistar rats were injected with LPS (0.05 mg/kg i.p.) or saline on postnatal days (PNDs) 3 and 5, and later subjected to the formalin test at PNDs 7, 13, and 22. One hour after formalin injection into the plantar hindpaw, animals were euthanized (Ketamine, 100 mg/kg i.p.) and transverse slices from the lumbosacral spinal cord were prepared. Whole-cell patch-clamp recordings were made from SDH neurons (KCH3SO4-based internal, 22–24°C) on the ipsi- and contralateral sides of the spinal cord. Depolarising current steps were injected into SDH neurons to categorize action potential (AP) discharge. In both saline- and LPS-treated rats we observed age-related increases the percentage of neurons exhibiting tonic-firing, with concurrent decreases in single-spiking, between PND 7 and 22. In contrast, neonatal exposure to LPS failed to alter the proportions of AP discharge patterns at any age examined. We also assessed the subthreshold currents that determine AP discharge in SDH neurons. The rapid outward potassium current, IAr decreased in prevalence with age, but was susceptible to neonatal LPS exposure. Peak IAr current amplitude was greater in ipsilateral vs. contralateral SDH neurons from LPS-treated rats. Spontaneous excitatory synaptic currents (sEPSCs) were recorded to assess network excitability. Age-related increases were observed in sEPSC frequency and time course, but not peak amplitude, in both saline- and LPS-treated rats. Furthermore, sEPSC frequency was higher in ipsilateral vs. contralateral SDH neurons in LPS-treated animals. Taken together, these data suggest a neonatal immune challenge does not markedly affect the intrinsic properties of SDH neurons, however, it can increase the excitability of local spinal cord networks via altering the properties of rapid A-type currents and excitatory synaptic connections. These changes, made in neurons within spinal cord pain circuits, have the capacity to alter nociceptive signaling in the ascending pain pathway.
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Affiliation(s)
- Melissa A Tadros
- Faculty of Health and Hunter Medical Research Institute, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
| | - Ihssane Zouikr
- Laboratory for Molecular Mechanisms of Thalamus Development, RIKEN, Wako, Saitama, Japan
| | - Deborah M Hodgson
- Laboratory of Neuroimmunology, School of Psychology, University of Newcastle, Callaghan, NSW, Australia
| | - Robert J Callister
- Faculty of Health and Hunter Medical Research Institute, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW, Australia
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Lucas-Romero J, Rivera-Arconada I, Roza C, Lopez-Garcia JA. Origin and classification of spontaneous discharges in mouse superficial dorsal horn neurons. Sci Rep 2018; 8:9735. [PMID: 29950700 PMCID: PMC6021406 DOI: 10.1038/s41598-018-27993-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Accepted: 06/13/2018] [Indexed: 12/24/2022] Open
Abstract
Superficial laminae of the spinal cord possess a considerable number of neurons with spontaneous activity as reported in vivo and in vitro preparations of several species. Such neurons may play a role in the development of the nociceptive system and/or in the spinal coding of somatosensory signals. We have used electrophysiological techniques in a horizontal spinal cord slice preparation from adult mice to investigate how this activity is generated and what are the main patterns of activity that can be found. The results show the existence of neurons that fire regularly and irregularly. Within each of these main types, it was possible to distinguish patterns of spontaneous activity formed by single action potentials and different types of bursts according to intra-burst firing frequency. Activity in neurons with irregular patterns was blocked by a mixture of antagonists of the main neurotransmitter receptors present in the cord. Approximately 82% of neurons with a regular firing pattern were insensitive to synaptic antagonists but their activity was inhibited by specific ion channel blockers. It is suggested that these neurons generate endogenous activity due to the functional expression of hyperpolarisation-activated and persistent sodium currents driving the activity of irregular neurons.
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Affiliation(s)
- Javier Lucas-Romero
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Ivan Rivera-Arconada
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Carolina Roza
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain
| | - Jose A Lopez-Garcia
- Department of Systems Biology, Universidad de Alcala, Alcala de Henares, 28871, Madrid, Spain.
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Uddin O, Studlack P, Akintola T, Raver C, Castro A, Masri R, Keller A. Amplified parabrachial nucleus activity in a rat model of trigeminal neuropathic pain. NEUROBIOLOGY OF PAIN 2018; 3:22-30. [PMID: 29862375 PMCID: PMC5973803 DOI: 10.1016/j.ynpai.2018.02.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The parabrachial (PB) complex mediates both ascending nociceptive signaling and descending pain modulatory information in the affective/emotional pain pathway. We hypothesized that PB hyperactivity influences chronic pain behavior after trigeminal nerve injury in rats. Following induction of neuropathic pain using the chronic constriction injury of the infraorbital nerve (CCI-ION) model, rats displayed spontaneous markers of pain and mechanical hyperalgesia extending beyond the receptive field of the injured nerve. PB neurons recorded from rats with CCI-ION displayed amplified activity, manifesting as significantly longer responses to sensory stimuli, compared to shams. These findings suggest that chronic neuropathic pain involves PB hyperactivity.
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Affiliation(s)
- Olivia Uddin
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States.,Program in Neuroscience, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
| | - Paige Studlack
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States.,Program in Neuroscience, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
| | - Titilola Akintola
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
| | - Charles Raver
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
| | - Alberto Castro
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States.,Program in Neuroscience, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
| | - Radi Masri
- Program in Neuroscience, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States.,Department of Advanced Oral Sciences and Therapeutics, University of Maryland School of Dentistry, 650 W. Baltimore St, Baltimore, MD 21201, United States
| | - Asaf Keller
- Department of Anatomy and Neurobiology, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States.,Program in Neuroscience, University of Maryland School of Medicine, 20 Penn St, HSF-II S251, Baltimore, MD 21201, United States
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Bernal Sierra YA, Haseleu J, Kozlenkov A, Bégay V, Lewin GR. Genetic Tracing of Ca v3.2 T-Type Calcium Channel Expression in the Peripheral Nervous System. Front Mol Neurosci 2017; 10:70. [PMID: 28360836 PMCID: PMC5350092 DOI: 10.3389/fnmol.2017.00070] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Accepted: 03/01/2017] [Indexed: 02/01/2023] Open
Abstract
Characterizing the distinct functions of the T-type ion channel subunits Cav3.1, 3.2 or 3.3 has proven difficult due to their highly conserved amino-acid sequences and the lack of pharmacological blockers specific for each subunit. To precisely determine the expression pattern of the Cav3.2 channel in the nervous system we generated two knock-in mouse strains that express EGFP or Cre recombinase under the control of the Cav3.2 gene promoter. We show that in the brains of these animals, the Cav3.2 channel is predominantly expressed in the dentate gyrus of the hippocampus. In the peripheral nervous system, the activation of the promoter starts at E9.5 in neural crest cells that will give rise to dorsal root ganglia (DRG) neurons, but not sympathetic neurons. As development progresses the number of DRG cells expressing the Cav3.2 channel reaches around 7% of the DRG at E16.5, and remains constant until E18.5. Characterization of sensory neuron subpopulations at E18.5 showed that EGFP+ cells are a heterogeneous population consisting mainly of TrkB+ and TrkC+ cells, while only a small percentage of DRG cells were TrkA+. Genetic tracing of the sensory nerve end-organ innervation of the skin showed that the activity of the Cav3.2 channel promoter in sensory progenitors marks many mechanoreceptor and nociceptor endings, but spares slowly adapting mechanoreceptors with endings associated with Merkel cells. Our genetic analysis reveals for the first time that progenitors that express the Cav3.2 T-type calcium channel, defines a sensory specific lineage that populates a large proportion of the DRG. Using our Cav3.2-Cre mice together with AAV viruses containing a conditional fluorescent reporter (tdTomato) we could also show that Cre expression is largely restricted to two functionally distinct sensory neuron types in the adult ganglia. Cav3.2 positive neurons innervating the skin were found to only form lanceolate endings on hair follicles and are probably identical to D-hair receptors. A second population of nociceptive sensory neurons expressing the Cav3.2 gene was found to be positive for the calcitonin-gene related peptide but these neurons are deep tissue nociceptors that do not innervate the skin.
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Affiliation(s)
- Yinth A Bernal Sierra
- Department of Neuroscience, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin Berlin, Germany
| | - Julia Haseleu
- Department of Neuroscience, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin Berlin, Germany
| | - Alexey Kozlenkov
- Department of Neuroscience, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin Berlin, Germany
| | - Valérie Bégay
- Department of Neuroscience, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin Berlin, Germany
| | - Gary R Lewin
- Department of Neuroscience, Max Delbrück Center for Molecular Medicine in the Helmholtz Association and Charité - Universitätsmedizin Berlin Berlin, Germany
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Roza C, Mazo I, Rivera-Arconada I, Cisneros E, Alayón I, López-García JA. Analysis of spontaneous activity of superficial dorsal horn neurons in vitro: neuropathy-induced changes. Pflugers Arch 2016; 468:2017-2030. [PMID: 27726011 DOI: 10.1007/s00424-016-1886-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2016] [Revised: 09/06/2016] [Accepted: 09/26/2016] [Indexed: 01/17/2023]
Abstract
The superficial dorsal horn contains large numbers of interneurons which process afferent and descending information to generate the spinal nociceptive message. Here, we set out to evaluate whether adjustments in patterns and/or temporal correlation of spontaneous discharges of these neurons are involved in the generation of central sensitization caused by peripheral nerve damage. Multielectrode arrays were used to record from discrete groups of such neurons in slices from control or nerve damaged mice. Whole-cell recordings of individual neurons were also obtained. A large proportion of neurons recorded extracellularly showed well-defined patterns of spontaneous firing. Clock-like neurons (CL) showed regular discharges at ∼6 Hz and represented 9 % of the sample in control animals. They showed a tonic-firing pattern to direct current injection and depolarized membrane potentials. Irregular fast-burst neurons (IFB) produced short-lasting high-frequency bursts (2-5 spikes at ∼100 Hz) at irregular intervals and represented 25 % of the sample. They showed bursting behavior upon direct current injection. Of the pairs of neurons recorded, 10 % showed correlated firing. Correlated pairs always included an IFB neuron. After nerve damage, the mean spontaneous firing frequency was unchanged, but the proportion of CL increased significantly (18 %) and many of these neurons appeared to acquire a novel low-threshold A-fiber input. Similarly, the percentage of IFB neurons was unaltered, but synchronous firing was increased to 22 % of the pairs studied. These changes may contribute to transform spinal processing of nociceptive inputs following peripheral nerve damage. The specific roles that these neurons may play are discussed.
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Affiliation(s)
- Carolina Roza
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain
| | - Irene Mazo
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain
| | - Iván Rivera-Arconada
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain
| | - Elsa Cisneros
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain
| | - Ismel Alayón
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain
| | - José A López-García
- Dpto. Biología de Sistemas, Edificio de Medicina, Universidad de Alcalá, Campus Universitario, 28871, Alcalá de Henares, Madrid, Spain.
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Hu T, Liu N, Lv M, Ma L, Peng H, Peng S, Liu T. Lidocaine Inhibits HCN Currents in Rat Spinal Substantia Gelatinosa Neurons. Anesth Analg 2016; 122:1048-59. [PMID: 26756913 PMCID: PMC4791316 DOI: 10.1213/ane.0000000000001140] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
BACKGROUND Lidocaine, which blocks voltage-gated sodium channels, is widely used in surgical anesthesia and pain management. Recently, it has been proposed that the hyperpolarization-activated cyclic nucleotide (HCN) channel is one of the other novel targets of lidocaine. Substantia gelatinosa in the spinal dorsal horn, which plays key roles in modulating nociceptive information from primary afferents, comprises heterogeneous interneurons that can be electrophysiologically categorized by firing pattern. Our previous study demonstrated that a substantial proportion of substantia gelatinosa neurons reveal the presence of HCN current (Ih); however, the roles of lidocaine and HCN channel expression in different types of substantia gelatinosa neurons remain unclear. METHODS By using the whole-cell patch-clamp technique, we investigated the effect of lidocaine on Ih in rat substantia gelatinosa neurons of acute dissociated spinal cord slices. RESULTS We found that lidocaine rapidly decreased the peak Ih amplitude with an IC50 of 80 μM. The inhibition rate on Ih was not significantly different with a second application of lidocaine in the same neuron. Tetrodotoxin, a sodium channel blocker, did not affect lidocaine's effect on Ih. In addition, lidocaine shifted the half-activation potential of Ih from -109.7 to -114.9 mV and slowed activation. Moreover, the reversal potential of Ih was shifted by -7.5 mV by lidocaine. In the current clamp, lidocaine decreased the resting membrane potential, increased membrane resistance, delayed rebound depolarization latency, and reduced the rebound spike frequency. We further found that approximately 58% of substantia gelatinosa neurons examined expressed Ih, in which most of them were tonically firing. CONCLUSIONS Our studies demonstrate that lidocaine strongly inhibits Ih in a reversible and concentration-dependent manner in substantia gelatinosa neurons, independent of tetrodotoxin-sensitive sodium channels. Thus, our study provides new insight into the mechanism underlying the central analgesic effect of the systemic administration of lidocaine.
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Affiliation(s)
- Tao Hu
- From the Departments of *Pediatrics and †Anesthesiology, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, People's Republic of China; and ‡Center for Laboratory Medicine, The First Affiliated Hospital of Nanchang University, Nanchang, Jiangxi, People's Republic of China
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10
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Tadros MA, Fuglevand AJ, Brichta AM, Callister RJ. Intrinsic excitability differs between murine hypoglossal and spinal motoneurons. J Neurophysiol 2016; 115:2672-80. [PMID: 26936988 DOI: 10.1152/jn.01114.2015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 02/29/2016] [Indexed: 12/12/2022] Open
Abstract
Motoneurons differ in the behaviors they control and their vulnerability to disease and aging. For example, brain stem motoneurons such as hypoglossal motoneurons (HMs) are involved in licking, suckling, swallowing, respiration, and vocalization. In contrast, spinal motoneurons (SMs) innervating the limbs are involved in postural and locomotor tasks requiring higher loads and lower movement velocities. Surprisingly, the properties of these two motoneuron pools have not been directly compared, even though studies on HMs predominate in the literature compared with SMs, especially for adult animals. Here we used whole cell patch-clamp recording to compare the electrophysiological properties of HMs and SMs in age-matched neonatal mice (P7-P10). Passive membrane properties were remarkably similar in HMs and SMs, and afterhyperpolarization properties did not differ markedly between the two populations. HMs had narrower action potentials (APs) and a faster upstroke on their APs compared with SMs. Furthermore, HMs discharged APs at higher frequencies in response to both step and ramp current injection than SMs. Therefore, while HMs and SMs have similar passive properties, they differ in their response to similar levels of depolarizing current. This suggests that each population possesses differing suites of ion channels that allow them to discharge at rates matched to the different mechanical properties of the muscle fibers that drive their distinct motor functions.
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Affiliation(s)
- M A Tadros
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and
| | - A J Fuglevand
- Department of Physiology, College of Medicine, University of Arizona, Tucson, Arizona
| | - A M Brichta
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and
| | - R J Callister
- School of Biomedical Sciences and Pharmacy, Faculty of Health and Hunter Medical Research Institute, The University of Newcastle, Callaghan, New South Wales, Australia; and
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11
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李 凌, 张 达, 彭 斯, 吴 静, 蒋 昌, 柳 涛. [Rebound depolarization of substantia gelatinosa neurons and its modulatory mechanisms in rat spinal dorsal horn]. NAN FANG YI KE DA XUE XUE BAO = JOURNAL OF SOUTHERN MEDICAL UNIVERSITY 2016; 37:204-209. [PMID: 28219864 PMCID: PMC6779672 DOI: 10.3969/j.issn.1673-4254.2017.02.10] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Indexed: 06/06/2023]
Abstract
OBJECTIVE To investigate the rebound depolarization of substantia gelatinosa (SG) neurons in rat spinal dorsal horn and explore its modulatory mechanisms to provide better insights into rebound depolarization-related diseases. METHODS Parasagittal slices of the spinal cord were prepared from 3- to 5-week-old Sprague-Dawley rats. The electrophysiologic characteristics and responses to hyperpolarization stimulation were recorded using whole-cell patch-clamp technique. The effects of hyperpolarization-activated cyclic nucleotide gated cation (HCN) channel blockers and T-type calcium channel blockers on rebound depolarization of the neurons were studied. RESULTS A total of 63 SG neurons were recorded. Among them, 23 neurons showed no rebound depolarization, 19 neurons showed rebound depolarization without spikes, and 21 neurons showed rebound depolarization with spikes. The action potential thresholds of the neurons without rebound depolarization were significantly higher than those of the neurons with rebound depolarization and spikes (-28.7∓1.6 mV vs -36.0∓2.0 mV, P<0.05). The two HCN channel blockers CsCl and ZD7288 significantly delayed the latency of rebound depolarization with spike from 45.9∓11.6 ms to 121.6∓51.3 ms (P<0.05) and from 36.2∓10.3 ms to 73.6∓13.6 ms (P<0.05), respectively. ZD7288 also significantly prolonged the latency of rebound depolarization without spike from 71.9∓35.1 ms to 267.0∓68.8 ms (P<0.05). The T-type calcium channel blockers NiCl2 and mibefradil strongly decreased the amplitude of rebound depolarization with spike from 19.9∓6.3 mV to 9.5∓4.5 mV (P<0.05) and from 26.1∓9.4 mV to 15.5∓5.0 mV (P<0.05), respectively. Mibefradil also significantly decreased the amplitude of rebound depolarization without spike from 14.3∓3.0 mV to 7.9∓2.0 mV (P<0.05). CONCLUSION Nearly two-thirds of the SG neurons have rebound depolarizations modulated by HCN channel and T-type calcium channel.
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Affiliation(s)
- 凌超 李
- 南昌大学第一附属医院 疼痛科, 江西 南昌 330006Department of Pain Clinic
| | - 达颖 张
- 南昌大学第一附属医院 疼痛科, 江西 南昌 330006Department of Pain Clinic
| | - 斯聪 彭
- 南昌大学第一附属医院 儿科, 江西 南昌 330006Department of Pediatrics
| | - 静 吴
- 南昌大学第一附属医院 儿科, 江西 南昌 330006Department of Pediatrics
| | - 昌宇 蒋
- 深圳市南山医院韩济生院士疼痛医学工作站, 广东 深圳 518052Jisheng Han Academician Workstation for Pain Medicine, Nanshan Hosptal, Shenzhen 518052, China
| | - 涛 柳
- 南昌大学第一附属医院 儿科, 江西 南昌 330006Department of Pediatrics
- 南昌大学第一附属医院 医学科研中心, 江西 南昌 330006Center for Experimental Medicine, First Affiliated Hospital of Nanchang University, Nanchang, 330006, China
- 深圳市南山医院韩济生院士疼痛医学工作站, 广东 深圳 518052Jisheng Han Academician Workstation for Pain Medicine, Nanshan Hosptal, Shenzhen 518052, China
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