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1.
Cereb Cortex ; 28(2): 625-643, 2018 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-28069760

RESUMO

Skilled upper limb function heavily depends on the corticospinal tract. After bilateral lesions to this tract, motor control is disrupted but can be partially substituted by other motor systems to allow functional recovery. However, the remaining roles of motor cortex and especially of axotomized corticospinal neurons (CSNs) are not well understood. Using the single pellet retrieval task in adult rats, we induced significant recovery of skilled reaching after bilateral pyramidotomy by rehabilitative reaching training, and show that reach-related motor cortex activity, recorded in layer V, topographically reappeared shortly after axotomy. Using a chemogenetic neuronal silencing technique, we found that axotomized CSNs retained a crucial role for the recovered pellet retrieval success. The axotomized CSNs sprouted extensively in the red nucleus supplying new innervation to its magnocellular and parvocellular parts. Specific silencing of the rubrospinal tract (RST) also strongly abolished the recovered pellet retrieval success, suggesting a role of this cervically projecting nucleus in relaying cortical motor control. In summary, our results show that after bilateral corticospinal axotomy, motor cortex still actively engages in forelimb motor control and axotomized CSNs are crucially involved in the recovered reaching movement, potentially by relaying motor control via the RST.


Assuntos
Membro Anterior/fisiologia , Córtex Motor/fisiologia , Destreza Motora/fisiologia , Neurônios/fisiologia , Tratos Piramidais/fisiologia , Animais , Axotomia/métodos , Estimulação Elétrica/métodos , Feminino , Membro Anterior/inervação , Córtex Motor/diagnóstico por imagem , Tratos Piramidais/diagnóstico por imagem , Ratos , Ratos Long-Evans
2.
PLoS Biol ; 12(1): e1001763, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-24453941

RESUMO

Nogo-A is a membrane protein of the central nervous system (CNS) restricting neurite growth and synaptic plasticity via two extracellular domains: Nogo-66 and Nogo-A-Δ20. Receptors transducing Nogo-A-Δ20 signaling remained elusive so far. Here we identify the G protein-coupled receptor (GPCR) sphingosine 1-phosphate receptor 2 (S1PR2) as a Nogo-A-Δ20-specific receptor. Nogo-A-Δ20 binds S1PR2 on sites distinct from the pocket of the sphingolipid sphingosine 1-phosphate (S1P) and signals via the G protein G13, the Rho GEF LARG, and RhoA. Deleting or blocking S1PR2 counteracts Nogo-A-Δ20- and myelin-mediated inhibition of neurite outgrowth and cell spreading. Blockade of S1PR2 strongly enhances long-term potentiation (LTP) in the hippocampus of wild-type but not Nogo-A(-/-) mice, indicating a repressor function of the Nogo-A/S1PR2 axis in synaptic plasticity. A similar increase in LTP was also observed in the motor cortex after S1PR2 blockade. We propose a novel signaling model in which a GPCR functions as a receptor for two structurally unrelated ligands, a membrane protein and a sphingolipid. Elucidating Nogo-A/S1PR2 signaling platforms will provide new insights into regulation of synaptic plasticity.


Assuntos
Hipocampo/metabolismo , Córtex Motor/metabolismo , Proteínas da Mielina/genética , Plasticidade Neuronal/genética , Receptores de Lisoesfingolipídeo/genética , Animais , Proliferação de Células , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/genética , Subunidades alfa G12-G13 de Proteínas de Ligação ao GTP/metabolismo , Regulação da Expressão Gênica , Hipocampo/citologia , Potenciação de Longa Duração , Lisofosfolipídeos/metabolismo , Camundongos , Camundongos Knockout , Córtex Motor/citologia , Proteínas da Mielina/deficiência , Bainha de Mielina/genética , Bainha de Mielina/metabolismo , Neuritos/metabolismo , Proteínas Nogo , Pró-Proteína Convertases/genética , Pró-Proteína Convertases/metabolismo , Receptores de Lisoesfingolipídeo/antagonistas & inibidores , Receptores de Lisoesfingolipídeo/metabolismo , Serina Endopeptidases/genética , Serina Endopeptidases/metabolismo , Transdução de Sinais , Esfingosina/análogos & derivados , Esfingosina/metabolismo , Receptores de Esfingosina-1-Fosfato , Sinapses/metabolismo , Proteínas rho de Ligação ao GTP/genética , Proteínas rho de Ligação ao GTP/metabolismo , Proteína rhoA de Ligação ao GTP
3.
J Neurosci ; 34(40): 13399-410, 2014 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-25274818

RESUMO

Anatomically incomplete spinal cord injuries are often followed by considerable functional recovery in patients and animal models, largely because of processes of neuronal plasticity. In contrast to the corticospinal system, where sprouting of fibers and rearrangements of circuits in response to lesions have been well studied, structural adaptations within descending brainstem pathways and intraspinal networks are poorly investigated, despite the recognized physiological significance of these systems across species. In the present study, spontaneous neuroanatomical plasticity of severed bulbospinal systems and propriospinal neurons was investigated following unilateral C4 spinal hemisection in adult rats. Injection of retrograde tracer into the ipsilesional segments C3-C4 revealed a specific increase in the projection from the ipsilesional gigantocellular reticular nucleus in response to the injury. Substantial regenerative fiber sprouting of reticulospinal axons above the injury site was demonstrated by anterograde tracing. Regrowing reticulospinal fibers exhibited excitatory, vGLUT2-positive varicosities, indicating their synaptic integration into spinal networks. Reticulospinal fibers formed close appositions onto descending, double-midline crossing C3-C4 propriospinal neurons, which crossed the lesion site in the intact half of the spinal cord and recrossed to the denervated cervical hemicord below the injury. These propriospinal projections around the lesion were significantly enhanced after injury. Our results suggest that severed reticulospinal fibers, which are part of the phylogenetically oldest motor command system, spontaneously arborize and form contacts onto a plastic propriospinal relay, thereby bypassing the lesion. These rearrangements were accompanied by substantial locomotor recovery, implying a potential physiological relevance of the detour in restoration of motor function after spinal injury.


Assuntos
Bulbo/fisiologia , Vias Neurais/fisiologia , Plasticidade Neuronal/fisiologia , Neurônios/patologia , Formação Reticular/patologia , Traumatismos da Medula Espinal/patologia , Animais , Axônios , Contagem de Células , Modelos Animais de Doenças , Feminino , Lateralidade Funcional/fisiologia , Proteínas da Membrana Plasmática de Transporte de GABA/metabolismo , Atividade Motora/fisiologia , Vias Neurais/efeitos dos fármacos , Vias Neurais/metabolismo , Ratos , Ratos Endogâmicos Lew , Recuperação de Função Fisiológica , Formação Reticular/metabolismo , Medula Espinal/efeitos dos fármacos , Medula Espinal/patologia , Traumatismos da Medula Espinal/fisiopatologia , Proteína Vesicular 1 de Transporte de Glutamato/metabolismo , Proteína Vesicular 2 de Transporte de Glutamato/metabolismo
4.
J Neurosci ; 34(26): 8685-98, 2014 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-24966370

RESUMO

The membrane protein Nogo-A is known as an inhibitor of axonal outgrowth and regeneration in the CNS. However, its physiological functions in the normal adult CNS remain incompletely understood. Here, we investigated the role of Nogo-A in cortical synaptic plasticity and motor learning in the uninjured adult rodent motor cortex. Nogo-A and its receptor NgR1 are present at cortical synapses. Acute treatment of slices with function-blocking antibodies (Abs) against Nogo-A or against NgR1 increased long-term potentiation (LTP) induced by stimulation of layer 2/3 horizontal fibers. Furthermore, anti-Nogo-A Ab treatment increased LTP saturation levels, whereas long-term depression remained unchanged, thus leading to an enlarged synaptic modification range. In vivo, intrathecal application of Nogo-A-blocking Abs resulted in a higher dendritic spine density at cortical pyramidal neurons due to an increase in spine formation as revealed by in vivo two-photon microscopy. To investigate whether these changes in synaptic plasticity correlate with motor learning, we trained rats to learn a skilled forelimb-reaching task while receiving anti-Nogo-A Abs. Learning of this cortically controlled precision movement was improved upon anti-Nogo-A Ab treatment. Our results identify Nogo-A as an influential molecular modulator of synaptic plasticity and as a regulator for learning of skilled movements in the motor cortex.


Assuntos
Aprendizagem/fisiologia , Potenciação de Longa Duração/fisiologia , Córtex Motor/fisiologia , Destreza Motora/fisiologia , Proteínas da Mielina/metabolismo , Animais , Masculino , Córtex Motor/metabolismo , Proteínas da Mielina/genética , Proteínas Nogo , Ratos , Ratos Sprague-Dawley , Sinapses/metabolismo , Sinapses/fisiologia
5.
BJU Int ; 115 Suppl 6: 8-15, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25597776

RESUMO

OBJECTIVES: To develop a urodynamic model incorporating external urethral sphincter (EUS) electromyography (EMG) in awake rats. MATERIALS AND METHODS: Bladder catheters and EUS EMG electrodes were implanted in female Sprague Dawley rats. Assessments were performed in awake, lightly restrained rats on postoperative day 12-14. Measurements were repeated in the same rat on day 16 under urethane anaesthesia. Urodynamics and EUS EMG were performed simultaneously. In addition, serum creatinine and bladder histology was assessed. RESULTS: No significant differences in urodynamic parameters were found between bladder catheter only vs bladder catheter and EUS EMG electrode groups. Urethane anaesthesia evoked prominent changes in both urodynamic parameters and EUS EMG. Serum creatinine was within the normal limits in all rats. Bladder weight and bladder wall thickness were significantly increased in both the bladder catheter only and the bladder catheter and EUS EMG group compared with controls. CONCLUSIONS: Our novel urodynamic model allows repetitive measurements of both bladder and EUS function at different time points in the same rat under fully awake conditions and opens promising avenues to investigate lower urinary tract dysfunction in a translational approach.


Assuntos
Modelos Animais , Uretra/fisiologia , Urodinâmica/fisiologia , Anestésicos Intravenosos/farmacologia , Animais , Eletromiografia , Feminino , Contração Muscular/fisiologia , Pressão , Ratos Sprague-Dawley , Uretana/farmacologia , Micção/fisiologia
6.
Brain ; 137(Pt 6): 1716-32, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24736305

RESUMO

Anatomical plasticity such as fibre growth and the formation of new connections in the cortex and spinal cord is one known mechanism mediating functional recovery after damage to the central nervous system. Little is known about anatomical plasticity in the brainstem, which contains key locomotor regions. We compared changes of the spinal projection pattern of the major descending systems following a cervical unilateral spinal cord hemisection in adult rats. As in humans (Brown-Séquard syndrome), this type of injury resulted in a permanent loss of fine motor control of the ipsilesional fore- and hindlimb, but for basic locomotor functions substantial recovery was observed. Antero- and retrograde tracings revealed spontaneous changes in spinal projections originating from the reticular formation, in particular from the contralesional gigantocellular reticular nucleus: more reticulospinal fibres from the intact hemicord crossed the spinal midline at cervical and lumbar levels. The intact-side rubrospinal tract showed a statistically not significant tendency towards an increased number of midline crossings after injury. In contrast, the corticospinal and the vestibulospinal tract, as well as serotonergic projections, showed little or no side-switching in this lesion paradigm. Spinal adaptations were accompanied by modifications at higher levels of control including side-switching of the input to the gigantocellular reticular nuclei from the mesencephalic locomotor region. Electrolytic microlesioning of one or both gigantocellular reticular nuclei in behaviourally recovered rats led to the reappearance of the impairments observed acutely after the initial injury showing that anatomical plasticity in defined brainstem motor networks contributes significantly to functional recovery after injury of the central nervous system.


Assuntos
Tronco Encefálico/fisiopatologia , Locomoção/fisiologia , Regeneração Nervosa/fisiologia , Plasticidade Neuronal/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Tronco Encefálico/patologia , Modelos Animais de Doenças , Feminino , Lateralidade Funcional/fisiologia , Ratos , Recuperação de Função Fisiológica/fisiologia , Traumatismos da Medula Espinal/patologia
7.
Brain ; 137(Pt 3): 739-56, 2014 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24355710

RESUMO

Adult Long Evans rats received a photothrombotic stroke that destroyed >90% of the sensorimotor cortex unilaterally; they were subsequently treated intrathecally for 2 weeks with a function blocking antibody against the neurite growth inhibitory central nervous system protein Nogo-A. Fine motor control of skilled forelimb grasping improved to 65% of intact baseline performance in the anti-Nogo-A treated rats, whereas control antibody treated animals recovered to only 20% of baseline scores. Bilateral retrograde tract tracing with two different tracers from the intact and the denervated side of the cervical spinal cord, at different time points post-lesion, indicated that the intact corticospinal tract had extensively sprouted across the midline into the denervated spinal hemicord. The original axonal arbours of corticospinal tract fibres that had recrossed the midline were subsequently withdrawn, leading to a complete side-switch in the projection of a subpopulation of contralesional corticospinal tract axons. Anterograde tracing from the contralesional cortex showed a 2-3-fold increase of midline crossing fibres and additionally a massive sprouting of the pre-existing ipsilateral ventral corticospinal tract fibres throughout the entire cervical enlargement of the anti-Nogo-A antibody-treated rats compared to the control group. The laminar distribution pattern of the ipsilaterally projecting corticospinal tract fibres was similar to that in the intact spinal cord. These plastic changes were paralleled by a somatotopic reorganization of the contralesional motor cortex where the formation of an ipsilaterally projecting forelimb area was observed. Intracortical microstimulation of the contralesional motor cortex revealed that low threshold currents evoked ipsilateral movements and electromyography responses at frequent cortical sites in the anti-Nogo-A, but not in the control antibody-treated animals. Subsequent transection of the spared corticospinal tract in chronically recovered animals, treated with anti-Nogo-A, led to a reappearance of the initial lesion deficit observed after the stroke lesion. These results demonstrate a somatotopic side switch anatomically and functionally in the projection of adult corticospinal neurons, induced by the destruction of one sensorimotor cortex and the neutralization of the CNS growth inhibitory protein Nogo-A.


Assuntos
Anticorpos Bloqueadores/administração & dosagem , Córtex Motor/fisiopatologia , Proteínas da Mielina/antagonistas & inibidores , Proteínas da Mielina/imunologia , Regeneração Nervosa/imunologia , Plasticidade Neuronal/imunologia , Acidente Vascular Cerebral/fisiopatologia , Animais , Anticorpos Bloqueadores/farmacologia , Comportamento Animal , Vértebras Cervicais , Eletromiografia , Membro Anterior/inervação , Membro Anterior/fisiopatologia , Lateralidade Funcional/fisiologia , Córtex Motor/imunologia , Proteínas da Mielina/biossíntese , Proteínas Nogo , Tratos Piramidais/imunologia , Tratos Piramidais/fisiopatologia , Ratos , Ratos Long-Evans , Acidente Vascular Cerebral/imunologia , Resultado do Tratamento
8.
Neuroimage ; 87: 72-9, 2014 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-24185021

RESUMO

Thoracic spinal cord injured rats rely largely on forelimbs to walk, as their hindlimbs are dysfunctional. This increased limb use is accompanied by expansion of the cortical forelimb sensory representation. It is unclear how quickly the representational changes occur and whether they are at all related to the behavioral adaptation. Using blood oxygenation level dependent functional mangetic resonance imaging (BOLD-fMRI) we show that major plastic changes of the somato-sensory map can occur as early as one day after injury. The extent of map increase was variable between animals, and some animals showed a reduction in map size. However, at three or seven days after injury a significant enhancement of the forelimb representation was evident in all the animals. In a behavioral test for precise limb control, crossing of a horizontal ladder, the injured rats relied almost entirely on their forelimbs; they initially made more mistakes than at 7 days post injury. Remarkably, in the individual animals the behavioral performance seen at seven days was proportional to the physiological change present at one day after injury. The rapid increase in cortical representation of the injury-spared body part may provide the additional neural substrate necessary for high level behavioral adaptation.


Assuntos
Membro Anterior/inervação , Córtex Somatossensorial/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Envelhecimento , Animais , Feminino , Imageamento por Ressonância Magnética , Ratos , Ratos Endogâmicos Lew , Fatores de Tempo
9.
Eur J Neurosci ; 38(6): 2946-61, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23790207

RESUMO

Anti-Nogo-A antibody and chondroitinase ABC (ChABC) enzyme are two promising treatments that promote functional recovery after spinal cord injury (SCI). Treatment with them has encouraged axon regeneration, sprouting and functional recovery in a variety of spinal cord and central nervous system injury models. The two compounds work, in part, through different mechanisms, so it is possible that their effects will be additive. In this study, we used a rat cervical partial SCI model to explore the effectiveness of a combination of anti-Nogo-A, ChABC, and rehabilitation. We found that spontaneous recovery of forelimb functions reflects the extent of the lesion on the ipsilateral side. We applied a combination treatment with acutely applied anti-Nogo-A antibody followed by delayed ChABC treatment starting at 3 weeks after injury, and rehabilitation starting at 4 weeks, to accommodate the requirement that anti-Nogo-A be applied acutely, and that rehabilitation be given after the cessation of anti-Nogo-A treatment. We found that single treatment with either anti-Nogo-A or ChABC, combined with rehabilitation, produced functional recovery of similar magnitude. The combination treatment, however, was more effective. Both single treatments produced increases in sprouting and axon regeneration, but the combination treatment produced greater increases. Anti-Nogo-A stimulated growth of a greater number of axons with a diameter of > 3 µm, whereas ChABC treatment stimulated increased growth of finer axons with varicosities. These results point to different functions of Nogo-A and chondroitin sulfate proteoglycans in axonal regeneration. The combination of anti-Nogo-A, ChABC and rehabilitation shows promise for enhancing functional recovery after SCI.


Assuntos
Anticorpos/uso terapêutico , Condroitina ABC Liase/uso terapêutico , Proteínas da Mielina/imunologia , Recuperação de Função Fisiológica/efeitos dos fármacos , Traumatismos da Medula Espinal/tratamento farmacológico , Animais , Vértebras Cervicais , Quimioterapia Combinada , Masculino , Proteínas Nogo , Ratos
10.
bioRxiv ; 2023 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-36993220

RESUMO

Innate and goal-directed movements require a high-degree of trunk and appendicular muscle coordination to preserve body stability while ensuring the correct execution of the motor action. The spinal neural circuits underlying motor execution and postural stability are finely modulated by propriospinal, sensory and descending feedback, yet how distinct spinal neuron populations cooperate to control body stability and limb coordination remains unclear. Here, we identified a spinal microcircuit composed of V2 lineage-derived excitatory (V2a) and inhibitory (V2b) neurons that together coordinate ipsilateral body movements during locomotion. Inactivation of the entire V2 neuron lineage does not impair intralimb coordination but destabilizes body balance and ipsilateral limb coupling, causing mice to adopt a compensatory festinating gait and be unable to execute skilled locomotor tasks. Taken together our data suggest that during locomotion the excitatory V2a and inhibitory V2b neurons act antagonistically to control intralimb coordination, and synergistically to coordinate forelimb and hindlimb movements. Thus, we suggest a new circuit architecture, by which neurons with distinct neurotransmitter identities employ a dual-mode of operation, exerting either synergistic or opposing functions to control different facets of the same motor behavior.

11.
Cell Rep ; 42(11): 113282, 2023 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-38007688

RESUMO

Schwann cells respond to acute axon damage by transiently transdifferentiating into specialized repair cells that restore sensorimotor function. However, the molecular systems controlling repair cell formation and function are not well defined, and consequently, it is unclear whether this form of cellular plasticity has a role in peripheral neuropathies. Here, we identify Mitf as a transcriptional sensor of axon damage under the control of Nrg-ErbB-PI3K-PI5K-mTorc2 signaling. Mitf regulates a core transcriptional program for generating functional repair Schwann cells following injury and during peripheral neuropathies caused by CMT4J and CMT4D. In the absence of Mitf, core genes for epithelial-to-mesenchymal transition, metabolism, and dedifferentiation are misexpressed, and nerve repair is disrupted. Our findings demonstrate that Schwann cells monitor axonal health using a phosphoinositide signaling system that controls Mitf nuclear localization, which is critical for activating cellular plasticity and counteracting neural disease.


Assuntos
Traumatismos dos Nervos Periféricos , Doenças do Sistema Nervoso Periférico , Humanos , Doenças do Sistema Nervoso Periférico/metabolismo , Células de Schwann/metabolismo , Axônios/metabolismo , Transdução de Sinais/fisiologia , Plasticidade Celular , Regeneração Nervosa/fisiologia , Traumatismos dos Nervos Periféricos/genética , Traumatismos dos Nervos Periféricos/metabolismo , Nervo Isquiático/metabolismo
12.
Eur J Neurosci ; 34(8): 1256-67, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21995852

RESUMO

To encourage re-establishment of functional innervation of ipsilateral lumbar motoneurons by descending fibers after an intervening lateral thoracic (T10) hemisection (Hx), we treated adult rats with the following agents: (i) anti-Nogo-A antibodies to neutralize the growth-inhibitor Nogo-A; (ii) neurotrophin-3 (NT-3) via engineered fibroblasts to promote neuron survival and plasticity; and (iii) the NMDA-receptor 2d (NR2d) subunit via an HSV-1 amplicon vector to elevate NMDA receptor function by reversing the Mg(2+) block, thereby enhancing synaptic plasticity and promoting the effects of NT-3. Synaptic responses evoked by stimulation of the ventrolateral funiculus ipsilateral and rostral to the Hx were recorded intracellularly from ipsilateral lumbar motoneurons. In uninjured adult rats short-latency (1.7-ms) monosynaptic responses were observed. After Hx these monosynaptic responses were abolished. In the Nogo-Ab + NT-3 + NR2d group, long-latency (approximately 10 ms), probably polysynaptic, responses were recorded and these were not abolished by re-transection of the spinal cord through the Hx area. This suggests that these novel responses resulted from new connections established around the Hx. Anterograde anatomical tracing from the cervical grey matter ipsilateral to the Hx revealed increased numbers of axons re-crossing the midline below the lesion in the Nogo-Ab + NT-3 + NR2d group. The combined treatment resulted in slightly better motor function in the absence of adverse effects (e.g. pain). Together, these results suggest that the combination treatment with Nogo-Ab + NT-3 + NR2d can produce a functional 'detour' around the lesion in a laterally hemisected spinal cord. This novel combination treatment may help to improve function of the damaged spinal cord.


Assuntos
Anticorpos Monoclonais/uso terapêutico , Proteínas da Mielina/imunologia , Neurotrofina 3/farmacologia , Subunidades Proteicas/farmacologia , Receptores de N-Metil-D-Aspartato/uso terapêutico , Traumatismos da Medula Espinal/patologia , Medula Espinal/efeitos dos fármacos , Animais , Comportamento Animal/fisiologia , Feminino , Humanos , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Neurônios Motores/citologia , Neurônios Motores/efeitos dos fármacos , Neurônios Motores/fisiologia , Neurotrofina 3/uso terapêutico , Proteínas Nogo , Subunidades Proteicas/uso terapêutico , Desempenho Psicomotor , Ratos , Ratos Sprague-Dawley , Medula Espinal/patologia , Traumatismos da Medula Espinal/tratamento farmacológico , Traumatismos da Medula Espinal/fisiopatologia
13.
Science ; 372(6540): 385-393, 2021 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-33888637

RESUMO

Motor and sensory functions of the spinal cord are mediated by populations of cardinal neurons arising from separate progenitor lineages. However, each cardinal class is composed of multiple neuronal types with distinct molecular, anatomical, and physiological features, and there is not a unifying logic that systematically accounts for this diversity. We reasoned that the expansion of new neuronal types occurred in a stepwise manner analogous to animal speciation, and we explored this by defining transcriptomic relationships using a top-down approach. We uncovered orderly genetic tiers that sequentially divide groups of neurons by their motor-sensory, local-long range, and excitatory-inhibitory features. The genetic signatures defining neuronal projections were tied to neuronal birth date and conserved across cardinal classes. Thus, the intersection of cardinal class with projection markers provides a unifying taxonomic solution for systematically identifying distinct functional subsets.


Assuntos
Vias Neurais , Neurônios/fisiologia , Medula Espinal/citologia , Transcriptoma , Animais , Medula Cervical/citologia , Feminino , Masculino , Camundongos , Neurônios Motores/fisiologia , Propriocepção , RNA-Seq , Células Receptoras Sensoriais/fisiologia , Análise de Célula Única , Análise Espacial , Medula Espinal/embriologia , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
14.
Neuron ; 102(3): 602-620.e9, 2019 05 08.
Artigo em Inglês | MEDLINE | ID: mdl-30902550

RESUMO

The rich functional diversity of the nervous system is founded in the specific connectivity of the underlying neural circuitry. Neurons are often preprogrammed to respond to multiple axon guidance signals because they use sequential guideposts along their pathways, but this necessitates a strict spatiotemporal regulation of intracellular signaling to ensure the cues are detected in the correct order. We performed a mouse mutagenesis screen and identified the Rho GTPase antagonist p190RhoGAP as a critical regulator of motor axon guidance. Rather than acting as a compulsory signal relay, p190RhoGAP uses a non-conventional GAP-independent mode to transiently suppress attraction to Netrin-1 while motor axons exit the spinal cord. Once in the periphery, a subset of axons requires p190RhoGAP-mediated inhibition of Rho signaling to target specific muscles. Thus, the multifunctional activity of p190RhoGAP emerges from its modular design. Our findings reveal a cell-intrinsic gate that filters conflicting signals, establishing temporal windows of signal detection.


Assuntos
Orientação de Axônios/genética , Receptor DCC/metabolismo , Proteínas Ativadoras de GTPase/genética , Neurônios Motores/metabolismo , Músculo Esquelético/inervação , Netrina-1/metabolismo , Proteínas Repressoras/genética , Animais , Células do Corno Anterior/metabolismo , Camundongos , Células-Tronco Embrionárias Murinas , Mutação
15.
J Neurosci ; 26(21): 5591-603, 2006 May 24.
Artigo em Inglês | MEDLINE | ID: mdl-16723516

RESUMO

Nogo-A, a membrane protein enriched in myelin of the adult CNS, inhibits neurite growth and regeneration; neutralizing antibodies or receptor blockers enhance regeneration and plasticity in the injured adult CNS and lead to improved functional outcome. Here we show that Nogo-A-specific knock-outs in backcrossed 129X1/SvJ and C57BL/6 mice display enhanced regeneration of the corticospinal tract after injury. Surprisingly, 129X1/SvJ Nogo-A knock-out mice had two to four times more regenerating fibers than C57BL/6 Nogo-A knock-out mice. Wild-type newborn 129X1/SvJ dorsal root ganglia in vitro grew a much higher number of processes in 3 d than C57BL/6 ganglia, confirming the stronger endogenous neurite growth potential of the 129X1/SvJ strain. cDNA microarrays of the intact and lesioned spinal cord of wild-type as well as Nogo-A knock-out animals showed a number of genes to be differentially expressed in the two mouse strains; many of them belong to functional categories associated with neurite growth, synapse formation, and inflammation/immune responses. These results show that neurite regeneration in vivo, under the permissive condition of Nogo-A deletion, and neurite outgrowth in vitro differ significantly in two widely used mouse strains and that Nogo-A is an important endogenous inhibitor of axonal regeneration in the adult spinal cord.


Assuntos
Axônios/fisiologia , Proteínas da Mielina/genética , Proteínas da Mielina/metabolismo , Regeneração Nervosa/fisiologia , Neuritos/fisiologia , Medula Espinal/fisiologia , Animais , Axônios/diagnóstico por imagem , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas da Mielina/deficiência , Neuritos/ultraestrutura , Proteínas Nogo , Especificidade da Espécie , Medula Espinal/citologia , Ultrassonografia
16.
Nat Protoc ; 12(1): 104-131, 2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27977023

RESUMO

Systemic application of therapeutics to the CNS tissue often results in subtherapeutic drug levels, because of restricted and selective penetration through the blood-brain barrier (BBB). Here, we give a detailed description of a standardized technique for intrathecal drug delivery in rodents, analogous to the technique used in humans. The intrathecal drug delivery method bypasses the BBB and thereby offers key advantages over oral or intravenous administration, such as maximized local drug doses with minimal systemic side effects. We describe how to deliver antibodies or drugs over several days or weeks from a s.c. minipump and a fine catheter inserted into the subdural space over the spinal cord (20 min operative time) or into the cisterna magna (10 min operative time). Drug levels can be sampled by quick and minimally invasive cerebrospinal fluid (CSF) collection from the cisterna magna (5 min procedure time). These techniques enable targeted application of any compound to the CNS for therapeutic studies in a wide range of CNS disease rodent models. Basic surgery skills are helpful for carrying out the procedures described in this protocol.


Assuntos
Cisterna Magna , Injeções Espinhais/métodos , Preparações Farmacêuticas/administração & dosagem , Espaço Subdural , Animais , Comportamento Animal/efeitos dos fármacos , Catéteres , Cisterna Magna/metabolismo , Feminino , Injeções Espinhais/instrumentação , Masculino , Preparações Farmacêuticas/metabolismo , Ratos , Espaço Subdural/metabolismo , Fatores de Tempo
17.
Neuron ; 91(4): 763-776, 2016 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-27478017

RESUMO

Motor behaviors such as walking or withdrawing the limb from a painful stimulus rely upon integrative multimodal sensory circuitry to generate appropriate muscle activation patterns. Both the cellular components and the molecular mechanisms that instruct the assembly of the spinal sensorimotor system are poorly understood. Here we characterize the connectivity pattern of a sub-population of lamina V inhibitory sensory relay neurons marked during development by the nuclear matrix and DNA binding factor Satb2 (ISR(Satb2)). ISR(Satb2) neurons receive inputs from multiple streams of sensory information and relay their outputs to motor command layers of the spinal cord. Deletion of the Satb2 transcription factor from ISR(Satb2) neurons perturbs their cellular position, molecular profile, and pre- and post-synaptic connectivity. These alterations are accompanied by abnormal limb hyperflexion responses to mechanical and thermal stimuli and during walking. Thus, Satb2 is a genetic determinant that mediates proper circuit development in a core sensory-to-motor spinal network.


Assuntos
Extremidades/fisiologia , Proteínas de Ligação à Região de Interação com a Matriz/fisiologia , Vias Neurais/fisiologia , Dor/fisiopatologia , Células Receptoras Sensoriais/fisiologia , Medula Espinal/fisiologia , Fatores de Transcrição/fisiologia , Caminhada/fisiologia , Animais , Interneurônios/fisiologia , Proteínas de Ligação à Região de Interação com a Matriz/genética , Camundongos , Camundongos Knockout , Mutação , Reflexo/fisiologia , Fatores de Transcrição/genética
18.
Neurorehabil Neural Repair ; 28(6): 594-605, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24519022

RESUMO

Functional recovery following central nervous system injuries is strongly influenced by rehabilitative training. In the clinical setting, the intensity of training and the level of motivation for a particular task are known to play important roles. With increasing neuroscience studies investigating the effects of training and rehabilitation, it is important to understand how the amount and type of training of individuals influences outcome. However, little is known about the influence of spontaneous "self-training" during daily life as it is often uncontrolled, not recorded, and mostly disregarded. Here, we investigated the effects of the intensity of self-training on motor skill acquisition in normal, intact rats and on the recovery of functional motor behavior following spinal cord injury in adult rats. We used a custom-designed small animal tracking system, "RatTrack," to continuously record the activity of multiple rats, simultaneously in a complex Natural Habitat-enriched environment. Naïve, adult rats performed high-intensity, self-motivated motor training, which resulted in them out-performing rats that were conventionally housed and trained on skilled movement tasks, for example, skilled prehension (grasping) and ladder walking. Following spinal cord injury the amount of self-training was correlated with improved functional recovery. These data suggest that high-impact, self-motivated training leads to superior skill acquisition and functional recovery than conventional training paradigms. These findings have important implications for the design of animal studies investigating rehabilitation and for the planning of human rehabilitation programs.


Assuntos
Comportamento Animal/fisiologia , Atividade Motora/fisiologia , Destreza Motora/fisiologia , Recuperação de Função Fisiológica/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Modelos Animais de Doenças , Feminino , Ratos , Ratos Long-Evans
19.
Sci Transl Med ; 5(208): 208ra146, 2013 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-24154600

RESUMO

In severe spinal cord injuries, the tracts conveying motor commands to the spinal cord are disrupted, resulting in paralysis, but many patients still have small numbers of spared fibers. We have found that excitatory deep brain stimulation (DBS) of the mesencephalic locomotor region (MLR), an important control center for locomotion in the brain, markedly improved hindlimb function in rats with chronic, severe, but incomplete spinal cord injury. The medial medullary reticular formation was essential for this effect. Functional deficits of rats with 20 to 30% spared reticulospinal fibers were comparable to patients able to walk but with strong deficits in strength and speed [for example, individuals with American Spinal Injury Association Impairment Scale (AIS)-D scores]. MLR DBS enabled close to normal locomotion in these rats. In more extensively injured animals, with less than 10% spared reticulospinal fibers, hindlimbs were almost fully paralyzed, comparable to wheelchair-bound patients (for example, AIS-A, B, and C). With MLR DBS, hindlimb function reappeared under gravity-released conditions during swimming. We propose that therapeutic MLR DBS using the brain's own motor command circuits may offer a potential new approach to treat persistent gait disturbances in patients suffering from chronic incomplete spinal cord injury.


Assuntos
Estimulação Encefálica Profunda , Membro Posterior/fisiologia , Membro Posterior/fisiopatologia , Locomoção/fisiologia , Mesencéfalo/fisiopatologia , Paresia/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Tronco Encefálico/patologia , Tronco Encefálico/fisiopatologia , Vértebras Lombares/patologia , Vértebras Lombares/fisiopatologia , Mesencéfalo/patologia , Paresia/patologia , Ratos , Traumatismos da Medula Espinal/patologia , Natação , Fatores de Tempo , Caminhada
20.
Nat Neurosci ; 13(1): 97-104, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20010824

RESUMO

Little is known about the functional role of axotomized cortical neurons that survive spinal cord injury. Large thoracic spinal cord injuries in adult rats result in impairments of hindlimb function. Using retrograde tracers, we found that axotomized corticospinal axons from the hindlimb sensorimotor cortex sprouted in the cervical spinal cord. Mapping of these neurons revealed the emergence of a new forelimb corticospinal projection from the rostral part of the former hindlimb cortex. Voltage-sensitive dye (VSD) imaging and blood-oxygen-level-dependent functional magnetic resonance imaging (BOLD fMRI) revealed a stable expansion of the forelimb sensory map, covering in particular the former hindlimb cortex containing the rewired neurons. Therefore, axotomized hindlimb corticospinal neurons can be incorporated into the sensorimotor circuits of the unaffected forelimb.


Assuntos
Mapeamento Encefálico , Membro Posterior/fisiopatologia , Regeneração Nervosa/fisiologia , Tratos Piramidais/patologia , Traumatismos da Medula Espinal/patologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Axotomia/métodos , Comportamento Animal , Vértebras Cervicais , Modelos Animais de Doenças , Feminino , Corantes Fluorescentes , Membro Anterior/fisiopatologia , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Potenciais da Membrana/fisiologia , Córtex Motor/irrigação sanguínea , Córtex Motor/fisiopatologia , Oxigênio/sangue , Tratos Piramidais/irrigação sanguínea , Pirazóis , Ratos , Ratos Endogâmicos Lew , Estatísticas não Paramétricas , Tiazóis
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