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1.
Mol Pharmacol ; 99(1): 49-59, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33298520

RESUMO

Voltage-gated sodium channels (Navs) are promising targets for analgesic and antiepileptic therapies. Although specificity between Nav subtypes may be desirable to target specific neural types, such as nociceptors in pain, many broadly acting Nav inhibitors are clinically beneficial in neuropathic pain and epilepsy. Here, we present the first systematic characterization of vixotrigine, a Nav blocker. Using recombinant systems, we find that vixotrigine potency is enhanced in a voltage- and use-dependent manner, consistent with a state-dependent block of Navs. Furthermore, we find that vixotrigine potently inhibits sodium currents produced by both peripheral and central nervous system Nav subtypes, with use-dependent IC50 values between 1.76 and 5.12 µM. Compared with carbamazepine, vixotrigine shows higher potency and more profound state-dependent inhibition but a similar broad spectrum of action distinct from Nav1.7- and Nav1.8-specific blockers. We find that vixotrigine rapidly inhibits Navs and prolongs recovery from the fast-inactivated state. In native rodent dorsal root ganglion sodium channels, we find that vixotrigine shifts steady-state inactivation curves. Based on these results, we conclude that vixotrigine is a broad-spectrum, state-dependent Nav blocker. SIGNIFICANCE STATEMENT: Vixotrigine blocks both peripheral and central voltage-gated sodium channel subtypes. Neurophysiological approaches in recombinant systems and sensory neurons suggest this block is state-dependent.


Assuntos
Éteres Fenílicos/metabolismo , Éteres Fenílicos/farmacologia , Prolina/análogos & derivados , Bloqueadores do Canal de Sódio Disparado por Voltagem/metabolismo , Bloqueadores do Canal de Sódio Disparado por Voltagem/farmacologia , Canais de Sódio Disparados por Voltagem/fisiologia , Animais , Células CHO , Cricetinae , Cricetulus , Relação Dose-Resposta a Droga , Feminino , Gânglios Espinais/efeitos dos fármacos , Gânglios Espinais/fisiologia , Células HEK293 , Humanos , Masculino , Éteres Fenílicos/química , Prolina/química , Prolina/metabolismo , Prolina/farmacologia , Ratos , Ratos Sprague-Dawley , Bloqueadores do Canal de Sódio Disparado por Voltagem/química , Canais de Sódio Disparados por Voltagem/química
2.
PLoS One ; 15(9): e0229475, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32915783

RESUMO

The importance of glial cells in the modulation of neuronal processes is now generally accepted. In particular, enormous progress in our understanding of astrocytes and microglia physiology in the central nervous system (CNS) has been made in recent years, due to the development of genetic and molecular toolkits. However, the roles of satellite glial cells (SGCs) and macrophages-the peripheral counterparts of astrocytes and microglia-remain poorly studied despite their involvement in debilitating conditions, such as pain. Here, we characterized in dorsal root ganglia (DRGs), different genetically-modified mouse lines previously used for studying astrocytes and microglia, with the goal to implement them for investigating DRG SGC and macrophage functions. Although SGCs and astrocytes share some molecular properties, most tested transgenic lines were found to not be suitable for studying selectively a large number of SGCs within DRGs. Nevertheless, we identified and validated two mouse lines: (i) a CreERT2 recombinase-based mouse line allowing transgene expression almost exclusively in SGCs and in the vast majority of SGCs, and (ii) a GFP-expressing line allowing the selective visualization of macrophages. In conclusion, among the tools available for exploring astrocyte functions, a few can be used for studying selectively a great proportion of SGCs. Thus, efforts remain to be made to characterize other available mouse lines as well as to develop, rigorously characterize and validate new molecular tools to investigate the roles of DRG SGCs, but also macrophages, in health and disease.


Assuntos
Gânglios Espinais/fisiologia , Macrófagos/fisiologia , Modelos Animais , Células Satélites Perineuronais/fisiologia , Animais , Astrócitos , Técnicas Biossensoriais/métodos , Células Cultivadas , Gânglios Espinais/citologia , Imuno-Histoquímica , Microscopia Intravital/métodos , Camundongos , Camundongos Transgênicos , Sondas Moleculares/química , Sondas Moleculares/genética , Imagem Óptica , Fótons , Cultura Primária de Células
3.
Proc Natl Acad Sci U S A ; 117(29): 17260-17268, 2020 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-32632007

RESUMO

Understanding how a network of interconnected neurons receives, stores, and processes information in the human brain is one of the outstanding scientific challenges of our time. The ability to reliably detect neuroelectric activities is essential to addressing this challenge. Optical recording using voltage-sensitive fluorescent probes has provided unprecedented flexibility for choosing regions of interest in recording neuronal activities. However, when recording at a high frame rate such as 500 to 1,000 Hz, fluorescence-based voltage sensors often suffer from photobleaching and phototoxicity, which limit the recording duration. Here, we report an approach called electrochromic optical recording (ECORE) that achieves label-free optical recording of spontaneous neuroelectrical activities. ECORE utilizes the electrochromism of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) thin films, whose optical absorption can be modulated by an applied voltage. Being based on optical reflection instead of fluorescence, ECORE offers the flexibility of an optical probe without suffering from photobleaching or phototoxicity. Using ECORE, we optically recorded spontaneous action potentials in cardiomyocytes, cultured hippocampal and dorsal root ganglion neurons, and brain slices. With minimal perturbation to cells, ECORE allows long-term optical recording over multiple days.


Assuntos
Eletrofisiologia/métodos , Neurônios/fisiologia , Poliestirenos , Tiofenos , Potenciais de Ação/fisiologia , Encéfalo/citologia , Encéfalo/fisiologia , Técnicas Eletroquímicas/métodos , Fenômenos Eletrofisiológicos , Corantes Fluorescentes , Gânglios Espinais/citologia , Gânglios Espinais/fisiologia , Humanos , Imagem Óptica , Óptica e Fotônica/métodos
4.
Sci Rep ; 10(1): 10953, 2020 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-32616790

RESUMO

Anatomically incomplete spinal cord injuries can be followed by functional recovery mediated, in part, by the formation of intraspinal detour circuits. Here, we show that adult mice recover tactile and proprioceptive function following a unilateral dorsal column lesion. We therefore investigated the basis of this recovery and focused on the plasticity of the dorsal column-medial lemniscus pathway. We show that ascending dorsal root ganglion (DRG) axons branch in the spinal grey matter and substantially increase the number of these collaterals following injury. These sensory fibers exhibit synapsin-positive varicosities, indicating their integration into spinal networks. Using a monosynaptic circuit tracing with rabies viruses injected into the cuneate nucleus, we show the presence of spinal cord neurons that provide a detour pathway to the original target area of DRG axons. Notably the number of contacts between DRG collaterals and those spinal neurons increases by more than 300% after injury. We then characterized these interneurons and showed that the lesion triggers a remodeling of the connectivity pattern. Finally, using re-lesion experiments after initial remodeling of connections, we show that these detour circuits are responsible for the recovery of tactile and proprioceptive function. Taken together our study reveals that detour circuits represent a common blueprint for axonal rewiring after injury.


Assuntos
Gânglios Espinais/fisiologia , Regeneração Nervosa , Vias Neurais , Neurônios/fisiologia , Recuperação de Função Fisiológica , Células Receptoras Sensoriais/fisiologia , Traumatismos da Medula Espinal/prevenção & controle , Animais , Comportamento Animal , Gânglios Espinais/citologia , Camundongos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal , Neurônios/citologia , Traumatismos da Medula Espinal/etiologia , Traumatismos da Medula Espinal/patologia
5.
RNA ; 26(10): 1414-1430, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32522888

RESUMO

The majority of mouse and human genes are subject to alternative cleavage and polyadenylation (APA), which most often leads to the expression of two or more alternative length 3' untranslated region (3'-UTR) mRNA isoforms. In neural tissues, there is enhanced expression of APA isoforms with longer 3'-UTRs on a global scale, but the physiological relevance of these alternative 3'-UTR isoforms is poorly understood. Calmodulin 1 (Calm1) is a key integrator of calcium signaling that generates short (Calm1-S) and long (Calm1-L) 3'-UTR mRNA isoforms via APA. We found Calm1-L expression to be largely restricted to neural tissues in mice including the dorsal root ganglion (DRG) and hippocampus, whereas Calm1-S was more broadly expressed. smFISH revealed that both Calm1-S and Calm1-L were subcellularly localized to neural processes of primary hippocampal neurons. In contrast, cultured DRG showed restriction of Calm1-L to soma. To investigate the in vivo functions of Calm1-L, we implemented a CRISPR-Cas9 gene editing strategy to delete a small region encompassing the Calm1 distal poly(A) site. This eliminated Calm1-L expression while maintaining expression of Calm1-S Mice lacking Calm1-L (Calm1ΔL/ΔL ) exhibited disorganized DRG migration in embryos, and reduced experience-induced neuronal activation in the adult hippocampus. These data indicate that Calm1-L plays functional roles in the central and peripheral nervous systems.


Assuntos
Regiões 3' não Traduzidas/genética , Sistemas CRISPR-Cas/genética , Calmodulina/genética , Gânglios Espinais/fisiologia , Hipocampo/fisiologia , Neurônios/fisiologia , Isoformas de RNA/genética , RNA Mensageiro/genética , Animais , Repetições Palindrômicas Curtas Agrupadas e Regularmente Espaçadas/genética , Feminino , Edição de Genes/métodos , Camundongos , Camundongos Endogâmicos C57BL , Poliadenilação/genética , Gravidez
6.
Anesthesiology ; 132(5): 1212-1228, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32101975

RESUMO

BACKGROUND: The authors' previous studies have found that spinal protein kinase C γ expressing neurons are involved in the feed-forward inhibitory circuit gating mechanical allodynia in the superficial dorsal horn. The authors hypothesize that nerve injury enhances the excitability of spinal protein kinase C γ expressing interneurons due to disinhibition of the feed-forward inhibitory circuit, and enables Aß primary inputs to activate spinal protein kinase C γ expressing interneurons. METHODS: Prkcg-P2A-tdTomato mice were constructed using the clustered regularly interspaced short palindromic repeats and clustered regularly interspaced short palindromic repeats-associated nuclease 9 technology, and were used to analyze the electrophysiologic properties of spinal protein kinase C γ expressing neurons in both normal conditions and pathologic conditions induced by chronic constriction injury of the sciatic nerve. Patch-clamp whole cell recordings were used to identify the nature of the dynamic synaptic drive to protein kinase C γ expressing neurons. RESULTS: Aß fiber stimulation evoked a biphasic synaptic response in 42% (31 of 73) of protein kinase C γ expressing neurons. The inhibitory components of the biphasic synaptic response were blocked by both strychnine and bicuculline in 57% (16 of 28) of neurons. Toll-like receptor 5 immunoreactive fibers made close contact with protein kinase C γ expressing neurons. After nerve injury, the percentage of neurons double-labeled for c-fos and Prkcg-P2A-tdTomato in animals walking on a rotarod was significantly higher than that in the nerve injury animals (4.1% vs. 9.9%, 22 of 539 vs. 54 of 548,P < 0.001). Aß fiber stimulation evoked burst action potentials in 25.8% (8 of 31) of protein kinase C γ expressing neurons in control animals, while the proportion increased to 51.1% (23 of 45) in nerve injury animals (P = 0.027). CONCLUSIONS: The Prkcg-P2A-tdTomato mice the authors constructed provide a useful tool for further analysis on how the spinal allodynia gate works. The current study indicated that nerve injury enhanced the excitability of spinal protein kinase C γ expressing interneurons due to disinhibition of the feed-forward inhibitory circuit, and enabled Aß primary inputs to activate spinal protein kinase C γ expressing interneurons.


Assuntos
Gânglios Espinais/fisiologia , Hiperalgesia/fisiopatologia , Rede Nervosa/fisiologia , Inibição Neural/fisiologia , Sinapses/fisiologia , Animais , Feminino , Gânglios Espinais/química , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Rede Nervosa/química , Técnicas de Cultura de Órgãos , Gravidez , Distribuição Aleatória , Sinapses/química
7.
Exp Neurol ; 327: 113244, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32057794

RESUMO

A variety of barriers ensures the protection of the peripheral nervous system from noxious blood-borne or surrounding stimuli. In this review, anatomy and functioning of the blood nerve barrier (BNB) and the blood DRG barrier (BDB) will be presented and key tight junction proteins described: ZO-1, claudin-1, -3, -5, -11, -12, -19, occludin, and tricellulin. Different diseases can lead to or be accompanied by nerve barrier disruption; impairment of nerve barriers in turn worsens pathology. Peripheral nerve injury, diabetic neuropathy and inflammatory polyneuropathy cause an increased permeability of BNB and BDB. Knowledge and understanding of these mechanisms might ultimately lead to the invention of drugs to control barrier function and help ameliorating neurological diseases.


Assuntos
Barreira Hematoneural/fisiologia , Gânglios Espinais/fisiologia , Nervos Periféricos/fisiologia , Animais , Humanos , Ocludina/metabolismo , Permeabilidade , Proteínas de Junções Íntimas/metabolismo , Junções Íntimas/metabolismo
8.
FASEB J ; 34(1): 287-302, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31914619

RESUMO

Unique features of sensory neuron subtypes are manifest by their distinct physiological and pathophysiological functions. Using patch-clamp electrophysiology, Ca2+ imaging, calcitonin gene-related peptide release assay from tissues, protein biochemistry approaches, and behavioral physiology on pain models, this study demonstrates the diversity of sensory neuron pathophysiology is due in part to subtype-dependent sensitization of TRPV1 and TRPA1. Differential sensitization is influenced by distinct expression of inflammatory mediators, such as prostaglandin E2 (PGE2), bradykinin (BK), and nerve growth factor (NGF) as well as multiple kinases, including protein kinase A (PKA) and C (PKC). However, the co-expression and interaction of TRPA1 with TRPV1 proved to be the most critical for differential sensitization of sensory neurons. We identified N- and C-terminal domains on TRPV1 responsible for TRPA1-TRPV1 (A1-V1) complex formation. Ablation of A1-V1 complex with dominant-negative peptides against these domains substantially reduced the sensitization of TRPA1, as well as BK- and CFA-induced hypersensitivity. These data indicate that often occurring TRP channel complexes regulate diversity in neuronal sensitization and may provide a therapeutic target for many neuroinflammatory pain conditions.


Assuntos
Cálcio/metabolismo , Gânglios Espinais/fisiologia , Hipersensibilidade/patologia , Dor/patologia , Células Receptoras Sensoriais/fisiologia , Canal de Cátion TRPA1/fisiologia , Canais de Cátion TRPV/fisiologia , Animais , Gânglios Espinais/citologia , Hipersensibilidade/metabolismo , Masculino , Camundongos , Camundongos Knockout , Nociceptividade , Dor/metabolismo , Células Receptoras Sensoriais/citologia
9.
Am J Physiol Regul Integr Comp Physiol ; 318(3): R579-R589, 2020 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-31967850

RESUMO

In contrast to other species, humans are believed to lack hygroreceptors for sensing skin wetness. Yet, the molecular basis of human hygrosensation is currently unknown, and it remains unclear whether we possess a receptor-mediated sensing mechanism for skin wetness. The aim of this study was to assess the role of the cutaneous cold-sensitive transient receptor potential melastatin-8 (TRPM8) channel as a molecular mediator of human hygrosensation. To this end, we exploited both the thermal and chemical activation of TRPM8-expressing cutaneous Aδ cold thermoreceptors, and we assessed wetness sensing in healthy young men in response to 1) dry skin cooling in the TRPM8 range of thermosensitivity and 2) application of the TRPM8 agonist menthol. Our results indicate that 1) independently of contact with moisture, a cold-dry stimulus in the TRPM8 range of activation induced wetness perceptions across 12 different body regions and those wetness perceptions varied across the body following regional differences in cold sensitivity; and 2) independently of skin cooling, menthol-induced stimulation of TRPM8 triggered wetness perceptions that were greater than those induced by physical dry cooling and by contact with an aqueous cream containing actual moisture. For the first time, we show that the cutaneous cold-sensing TRPM8 channel plays the dual role of cold and wetness sensor in human skin and that this ion channel is a peripheral mediator of human skin wetness perception.


Assuntos
Temperatura Baixa , Temperatura Cutânea/fisiologia , Canais de Cátion TRPM/metabolismo , Termorreceptores/fisiologia , Temperatura Baixa/efeitos adversos , Gânglios Espinais/fisiologia , Humanos , Células Receptoras Sensoriais/fisiologia , Sensação Térmica/fisiologia , Canais de Receptores Transientes de Potencial/metabolismo
10.
Pain Pract ; 20(4): 399-404, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31725944

RESUMO

BACKGROUND: Stimulation of the dorsal root ganglion (DRG-S) has been shown to be an efficacious treatment option for refractory neuropathic pain syndromes. However, placement of the percutaneous leads for trial implantation can be challenging in patients with prior spinal surgical interventions resulting in anatomical changes and adhesions. METHODS: This technical report describes the transgrade placement of DRG-S leads in 4 patients with back pain surgery histories in whom secondary to specific anatomical pathologies the traditional anterograde placement of DRG-S leads was not feasible. RESULTS: We used a transgrade placement approach, entering superior and contralateral to the target level of placement, resulting in uncomplicated and effective placement of DRG-S leads. CONCLUSIONS: Transgrade lead placement for DRG-S may be an efficacious alternative to traditional anterograde DRG lead placement in cases where interlaminar access below the level of the DRG is not available, or desirable. Further studies are needed to clarify the safety and applicability of this approach.


Assuntos
Eletrodos Implantados , Gânglios Espinais/fisiologia , Neuralgia/terapia , Procedimentos Neurocirúrgicos/métodos , Estimulação da Medula Espinal/métodos , Idoso , Feminino , Humanos , Região Lombossacral , Masculino , Pessoa de Meia-Idade , Manejo da Dor/métodos , Resultado do Tratamento
11.
Exp Neurol ; 323: 113073, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31639375

RESUMO

During mammalian embryonic development sensory and motor axons interact as an integral part of the pathfinding process. During regeneration, however, little is known of their interactions with one another. It is thus possible that sensory axons might influence motor axon regeneration in ways not currently appreciated. To explore this possibility we have developed an organotypic model of post-natal nerve regeneration in which sensory and motor axons are color-coded by modality. Motor axons that express yellow fluorescent protein (YFP) and sensory axons that express red fluorescent protein (RFP) are blended within a three-dimensional segment of peripheral nerve. This nerve is then transected, allowing axons to interact with one another as they grow out on a collagen/laminin gel that is initially devoid of directional cues. Within hours it is apparent that sensory axons extend more rapidly than motor axons and precede them during the early stages of regeneration, the opposite of their developmental order. Motor axons thus enter an environment already populated with sensory axons, and they adhere to these axons throughout most of their course. As a result, motor axon growth is reduced dramatically. Physical delay of sensory regeneration, allowing motor axons to grow ahead, restores normal motor growth; direct axonal interactions on the gel, rather than some other aspect of the model, are thus responsible for motor inhibition. Potential mechanisms for this inhibition are explored by electroporating siRNA to the neural cell adhesion molecule (NCAM) and the L1 adhesion molecule (L1CAM) into dorsal root ganglia (DRGs) to block expression of these molecules by regenerating sensory axons. Although neither maneuver improved motor regeneration, the results were consistent with early receptor-mediated signaling among axons rather than physical adhesion as the mechanism of motor inhibition in this model.


Assuntos
Axônios/fisiologia , Neurônios Motores/fisiologia , Regeneração Nervosa/fisiologia , Células Receptoras Sensoriais/fisiologia , Animais , Técnicas de Cocultura/métodos , Gânglios Espinais/fisiologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Molécula L1 de Adesão de Célula Nervosa/metabolismo , Moléculas de Adesão de Célula Nervosa/metabolismo , Técnicas de Cultura de Órgãos/métodos , Nervos Periféricos/fisiologia , Medula Espinal/fisiologia
12.
Cell Rep ; 29(10): 2953-2960.e2, 2019 Dec 03.
Artigo em Inglês | MEDLINE | ID: mdl-31801063

RESUMO

Functionally distinct classes of dorsal root ganglia (DRG) somatosensory neurons arise from neural crest cells (NCCs) in two successive phases of differentiation assumed to be respectively and independently controlled by the proneural genes Neurog2 and Neurog1. However, the precise role of Neurog2 during this process remains unclear, notably because no neuronal loss has been reported hitherto in Neurog2-/- mutants. Here, we show that at trunk levels, Neurog2 deficiency impairs the production of subsets of all DRG neuron subtypes. We establish that this phenotype is highly dynamic and reflects multiple defects in NCC-derived progenitors, including somatosensory-to-melanocyte fate switch, apoptosis, and delayed differentiation which alters neuronal identity, all occurring during a narrow time window when Neurog2 temporarily controls onset of Neurog1 expression and neurogenesis. Collectively, these findings uncover a critical period of cell fate plasticity and vulnerability among somatosensory progenitors and establish that Neurog2 function in the developing DRG is broader than initially envisaged.


Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/metabolismo , Plasticidade Celular/fisiologia , Proteínas do Tecido Nervoso/metabolismo , Crista Neural/metabolismo , Animais , Diferenciação Celular/fisiologia , Gânglios Espinais/metabolismo , Gânglios Espinais/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Camundongos , Neurogênese/fisiologia , Neurônios/metabolismo , Neurônios/fisiologia
13.
J Neurosci ; 39(50): 9927-9939, 2019 12 11.
Artigo em Inglês | MEDLINE | ID: mdl-31672792

RESUMO

Primary afferent neurons convey somatosensory information to the CNS. Low-threshold mechanoreceptors are classified as slow-adapting (SA) or rapid-adapting (RA) based on whether or not they spike repetitively during sustained tactile stimulation; the former are subclassified as Type 1 or 2 based on the regularity of their spiking. Recording in vivo from DRGs of mice, we observed irregular- and regular-spiking units consistent with SA1 and SA2 low-threshold mechanoreceptors, but some units, which we labeled "semiregular," did not fit cleanly into the existing classification scheme. Analysis of their spiking revealed integer-multiple patterning in which spike trains comprised a fundamental interspike interval and multiples thereof. Integer-multiple-patterned spiking was reproduced by randomly removing spikes from an otherwise regular spike train, suggesting that semiregular units represent SA2 units in which some spikes are "missing." We hypothesized that missing spikes arose from intermittent failure of spikes to initiate or to propagate. Intermittent failure of spike initiation was ruled out by several observations: integer-multiple-patterned spiking was not induced by intradermal lidocaine, was independent of stimulus modality (mechanical vs optogenetic), and could not be reproduced in a conductance-based model neuron given constant input. On the other hand, integer-multiple-patterned spiking was induced by application of lidocaine to the DRG, thus pinpointing intermittent failure of spike propagation as the basis for integer-multiple-patterned spiking. Indeed, half of all SA2 units exhibited some missing spikes, mostly at low rate (<5%), which suggests that axons are efficient in using the lowest safety factor capable of producing near-perfect propagation reliability.SIGNIFICANCE STATEMENT The impedance mismatch at axon branch points can impede spike propagation. Reliability of spike propagation across branch points remains an open question and is especially important for primary afferents whose spikes must cross a T-junction to reach the CNS. Past research on propagation reliability has relied almost entirely on simulations and in vitro experiments. Here, recording in vivo, we linked a distinctive pattern of spiking to the intermittent failure of spike propagation at the T-junction. The rarity of failures argues that safety factor is high under physiological conditions, yet the occurrence of such failures argues that safety factor is just high enough to ensure near-perfect reliability, consistent with a good balance between propagation reliability and energy efficiency.


Assuntos
Potenciais de Ação/fisiologia , Neurônios Aferentes/fisiologia , Percepção do Tato/fisiologia , Animais , Gânglios Espinais/fisiologia , Potenciais da Membrana/fisiologia , Camundongos , Estimulação Física , Tato
14.
Neuroscience ; 423: 98-108, 2019 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-31689490

RESUMO

Non-synaptic transmission is pervasive throughout the nervous system. It appears especially prevalent in peripheral ganglia, where non-synaptic interactions between neighboring cell bodies have been described in both physiological and pathological conditions, a phenomenon referred to as cross-depolarization (CD) and thought to play a role in sensory processing and chronic pain. CD has been proposed to be mediated by a chemical agent, but its identity has remained elusive. Here, we report that in the rat dorsal root ganglion (DRG), the P2Y1 purinergic receptor (P2RY1) plays an important role in regulating CD. The effect of P2RY1 is cell-type specific: pharmacological blockade of P2RY1 inhibited CD in A-type neurons while enhancing it in C-type neurons. In the nodose ganglion of the vagus, CD requires extracellular calcium in a large percentage of cells. In contrast, we show that in the DRG extracellular calcium appears to play no major role, pointing to a mechanistic difference between the two peripheral ganglia. Furthermore, we show that DRG glial cells also play a cell-type specific role in CD regulation. Fluorocitrate-induced glial inactivation had no effect on A-cells but enhanced CD in C-cells. These findings shed light on the mechanism of CD in the DRG and pave the way for further analysis of non-synaptic neuronal communication in sensory ganglia.


Assuntos
Comunicação Celular/fisiologia , Gânglios Espinais/fisiologia , Neurônios/fisiologia , Receptores Purinérgicos P2Y1/fisiologia , 2-Amino-5-fosfonovalerato/farmacologia , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Potenciais de Ação/fisiologia , Difosfato de Adenosina/análogos & derivados , Difosfato de Adenosina/farmacologia , Animais , Benzenossulfonatos/farmacologia , Cálcio/fisiologia , Citratos/farmacologia , Estimulação Elétrica , Masculino , Inibição Neural/fisiologia , Neuroglia/efeitos dos fármacos , Neuroglia/fisiologia , Neurônios/efeitos dos fármacos , Gânglio Nodoso/fisiologia , Piperazinas/farmacologia , Ratos , Receptores Purinérgicos P2Y1/efeitos dos fármacos
16.
Pain Physician ; 22(6): 601-611, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31775407

RESUMO

BACKGROUND: The recent interest in targeting the dorsal root ganglion (DRG) has led to the development of new techniques of electrode placement. In this article, we describe a new "Transgrade" approach to the DRG, accessing the contralateral interlaminar space and steering the lead out the opposite foramen. OBJECTIVES: The purpose of this study was to evaluate the Transgrade technique to the DRG in the management of focal neuropathic pain, predominately complex regional pain syndrome in terms of efficacy and safety. STUDY DESIGN: A retrospective, observational review of all patients selected for DRG stimulation using the Transgrade technique to the DRG. SETTING: Pain Management and Neuromodulation Centre, Guys and St. Thomas NHS Foundation Trust, London, United Kingdom. METHODS: Data were taken from a hospital password-protected database. All patients were contacted by telephone for Numeric Rating Scale (NRS-11) score, Patient Global Impression of Change (PGIC) score, and complications. A patient responder was defined as having a PGIC score of 6 or 7, and a 2-point reduction from baseline NRS-11. RESULTS: A total of 39 patients (46% women) with a mean age of 46 years (± 2) underwent a trial of DRG stimulation that resulted in an implantation rate of 82% (32 of 39). The responder rates, according to NRS-11 and PGIC results, were 87% (28 of 32) at 6 weeks and 66% (21 of 32) at a mean of 18 months (± 1.8) follow-up. Pocket pain was the most common complication, occurring in 7 of 32 (22%) patients, and the lead migration rate was 3 out of 57 leads placed (5.2%). A burst protocol was the favored method of stimulation in the majority of patients, 25 of 32 (78%). LIMITATIONS: Retrospective nature of design, small sample size. CONCLUSIONS: The Transgrade technique of placing DRG leads offers an alternative method that is safe and effective. New methods of stimulation to the DRG offer more choice and potentially better efficacy for patients with chronic neuropathic pain. KEY WORDS: Neuromodulation, dorsal root ganglion, neuropathic pain, complex regional pain syndrome, spinal cord stimulation, chronic pain, implantable neurostimulators, spinal nerve root stimulation.


Assuntos
Gânglios Espinais/fisiologia , Neuralgia/terapia , Manejo da Dor/métodos , Estimulação da Medula Espinal/métodos , Adulto , Dor Crônica/terapia , Síndromes da Dor Regional Complexa/terapia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Projetos de Pesquisa , Estudos Retrospectivos , Reino Unido
17.
Pain Physician ; 22(6): E627-E633, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31775416

RESUMO

BACKGROUND: Cervical vertigo commonly concurs in patients with neck pain, but the concurrent mechanism of these 2 symptoms still remains unclear. We previously reported a bidirectional segmental nerve fiber connection between cervical spinal and sympathetic ganglia, which provided a hypothesis that this connection between the 2 ganglia may be the anatomic basis for the concurrence of neck pain and cervical vertigo. However, this concurrent mechanism needs biochemical and functional evidence. OBJECTIVES: This study aimed to investigate a possible noradrenergic pathway between cervical spinal and sympathetic ganglia. STUDY DESIGN: We performed both clinical and laboratory research. Clinical observation was a prospective case-control study. SETTING: Clinical study took place in our hospital; laboratory study was in an orthopedic laboratory. METHODS: Cervical lamina block therapy used in patients with cervical vertigo was clinically evaluated; norepinephrine (NE) expressions in cervical sympathetic ganglia were analyzed using immunohistochemical staining after electrical stimulation to the cervical spinal ganglia; the influence of phentolamine local injection to the vertebrobasilar artery flow was experimentally measured. RESULTS: Cervical lamina block therapy could significantly shorten the clinical hospital stays of patients with cervical vertigo (P = 0.000) and improve vertebral artery flow (P < 0.05). NE expressions in superior cervical sympathetic ganglia (SCG) or inferior cervical sympathetic ganglia (ICG) increased significantly when ipsilateral C2 to C3 or C6 to C8 spinal ganglia were electrically stimulated, respectively. Adrenergic receptor block with phentolamine significantly inhibited the decrease of basilar artery (BA) flow induced by electrical stimulation of the cervical spinal ganglia. The change range of BA flow caused by stimulations of C2 to C3 and C6 to C8 spinal ganglia was more than that of C4 and C5. LIMITATIONS: The inpatients observed in this clinical study might be influenced by some factors including emotion, diet, sleep, and others. The limitations of the laboratory study included animal species and small sample size. CONCLUSIONS: Adrenergic system could play a part in cervical spinal ganglia altering the vertebrobasilar artery system. It could provide a neurochemical foundation between neck pain and vertigo, and that segmental functional connections exist between cervical spinal and sympathetic ganglia. KEY WORDS: Cervical vertigo, neck pain, cervical sympathetic ganglia, cervical spinal ganglia, noradrenaline.


Assuntos
Bloqueio Nervoso Autônomo/métodos , Gânglios Espinais/fisiologia , Gânglios Simpáticos/fisiologia , Cervicalgia/tratamento farmacológico , Vertigem/tratamento farmacológico , Adulto , Animais , Estudos de Casos e Controles , Vértebras Cervicais/efeitos dos fármacos , Vértebras Cervicais/inervação , Vértebras Cervicais/fisiologia , Feminino , Gânglios Espinais/efeitos dos fármacos , Gânglios Simpáticos/efeitos dos fármacos , Humanos , Masculino , Pessoa de Meia-Idade , Cervicalgia/epidemiologia , Cervicalgia/fisiopatologia , Estudos Prospectivos , Coelhos , Distribuição Aleatória , Vertigem/epidemiologia , Vertigem/fisiopatologia
18.
J Neural Eng ; 17(1): 016014, 2019 12 23.
Artigo em Inglês | MEDLINE | ID: mdl-31648208

RESUMO

OBJECTIVE: We have demonstrated previously that microstimulation in the dorsal root ganglia (DRG) can selectively evoke activity in primary afferent neurons in anesthetized cats. This study describes the results of experiments focused on characterizing the postural effects of DRG microstimulation in awake cats during quiet standing. APPROACH: To understand the parameters of stimulation that can affect these postural shifts, we measured changes in ground reaction forces (GRF) while varying stimulation location and amplitude. Four animals were chronically implanted at the L6 and L7 DRG with penetrating multichannel microelectrode arrays. During each week of testing, we identified electrode channels that recruited primary afferent neurons with fast (80-120 m s-1) and medium (30-75 m s-1) conduction velocities, and selected one channel to deliver current-controlled biphasic stimulation trains during quiet standing. MAIN RESULTS: Postural responses were identified by changes in GRFs and were characterized based on their magnitude and latency. During DRG microstimulation, animals did not exhibit obvious signs of distress or discomfort, which could be indicative of pain or aversion to a noxious sensation. Across 56 total weeks, 13 electrode channels evoked behavioral responses, as detected by a significant change in GRF. Stimulation amplitude modulated the magnitude of the GRF responses for these 13 channels (p  < 0.001). It was not possible to predict whether or not an electrode would drive a behavioral response based on information including conduction velocity, recruitment threshold, or the DRG in which it resided. SIGNIFICANCE: The distinct and repeatable effects on the postural response to low amplitude (<40 µA) DRG microstimulation support that this technique may be an effective way to restore somatosensory feedback after neurological injuries such as amputation.


Assuntos
Gânglios Espinais/fisiologia , Equilíbrio Postural/fisiologia , Vigília/fisiologia , Animais , Gatos , Estimulação Elétrica/instrumentação , Estimulação Elétrica/métodos , Masculino , Microeletrodos
19.
Toxins (Basel) ; 11(10)2019 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-31658776

RESUMO

In this work, we evaluate the effect of two peptides Sa12b (EDVDHVFLRF) and Sh5b (DVDHVFLRF-NH2) on Acid-Sensing Ion Channels (ASIC). These peptides were purified from the venom of solitary wasps Sphex argentatus argentatus and Isodontia harmandi, respectively. Voltage clamp recordings of ASIC currents were performed in whole cell configuration in primary culture of dorsal root ganglion (DRG) neurons from (P7-P10) CII Long-Evans rats. The peptides were applied by preincubation for 25 s (20 s in pH 7.4 solution and 5 s in pH 6.1 solution) or by co-application (5 s in pH 6.1 solution). Sa12b inhibits ASIC current with an IC50 of 81 nM, in a concentration-dependent manner when preincubation application was used. While Sh5b did not show consistent results having both excitatory and inhibitory effects on the maximum ASIC currents, its complex effect suggests that it presents a selective action on some ASIC subunits. Despite the similarity in their sequences, the action of these peptides differs significantly. Sa12b is the first discovered wasp peptide with a significant ASIC inhibitory effect.


Assuntos
Bloqueadores do Canal Iônico Sensível a Ácido/farmacologia , Canais Iônicos Sensíveis a Ácido/fisiologia , Gânglios Espinais/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Peptídeos/farmacologia , Animais , Células Cultivadas , Feminino , Gânglios Espinais/fisiologia , Masculino , Neurônios/fisiologia , Ratos Long-Evans , Vespas
20.
J Neurophysiol ; 122(6): 2591-2600, 2019 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-31642403

RESUMO

NaV1.8 channels play a crucial role in regulating the action potential in nociceptive neurons. A single nucleotide polymorphism in the human NaV1.8 gene SCN10A, A1073V (rs6795970, G>A), has been linked to the diminution of mechanical pain sensation as well as cardiac conduction abnormalities. Furthermore, studies have suggested that this polymorphism may result in a "loss-of-function" phenotype. In the present study, we performed genomic analysis of A1073V polymorphism presence in a cohort of patients undergoing sigmoid colectomy who provided information regarding perioperative pain and analgesic use. Homozygous carriers reported significantly reduced severity in postoperative abdominal pain compared with heterozygous and wild-type carriers. Homozygotes also trended toward using less analgesic/opiates during the postoperative period. We also heterologously expressed the wild-type and A1073V variant in rat superior cervical ganglion neurons. Electrophysiological testing demonstrated that the mutant NaV1.8 channels activated at more depolarized potentials compared with wild-type channels. Our study revealed that postoperative abdominal pain is diminished in homozygous carriers of A1073V and that this is likely due to reduced transmission of action potentials in nociceptive neurons. Our findings reinforce the importance of NaV1.8 and the A1073V polymorphism to pain perception. This information could be used to develop new predictive tools to optimize patient pain experience and analgesic use in the perioperative setting.NEW & NOTEWORTHY We present evidence that in a cohort of patients undergoing sigmoid colectomy, those homozygous for the NaV1.8 polymorphism (rs6795970) reported significantly lower abdominal pain scores than individuals with the homozygous wild-type or heterozygous genotype. In vitro electrophysiological recordings also suggest that the mutant NaV1.8 channel activates at more depolarizing potentials than the wild-type Na+ channel, characteristic of hypoactivity. This is the first report linking the rs6795970 mutation with postoperative abdominal pain in humans.


Assuntos
Dor Abdominal/genética , Colectomia , Fenômenos Eletrofisiológicos/fisiologia , Gânglios Espinais/fisiologia , Canal de Sódio Disparado por Voltagem NAV1.8/fisiologia , Nociceptividade/fisiologia , Dor Pós-Operatória/genética , Gânglio Cervical Superior/metabolismo , Sistema Nervoso Simpático/fisiologia , Idoso , Animais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Canal de Sódio Disparado por Voltagem NAV1.8/genética , Neurônios/fisiologia , Polimorfismo Genético , Ratos , Estudos Retrospectivos
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