RESUMO
The corticospinal tract (CST), descending from the frontoparietal cortex and traveling down to terminate at the anterior horn of the spinal cord to mediate voluntary movements, is frequently injured from the infarcted or hemorrhagic cerebrovascular insults due to stroke. Under the circumstances, motor dysfunction seriously affects the patient's quality of life. Acupuncture therapy has a sequelae, especially in improving motor deficits. In the present paper, we reviewed the current development of researches on acupuncture treatment of poststroke motor dysfunction and its biological mechanisms from 1) delaying patients' development of neuronal degeneration and white matter fibrosis (Wallerian degeneration), 2) improving patients' upper limb motor function and daily life ability by promoting the repair of white matter tracts and CST on the affected side, 3) promoting the compensation of CST on the healthy side, 4) reconstructing the motor conduction pathway to strengthen the bilateral brain connection in ex-perimental animals, and 5) strengthening the sprouting of the contralateral CST to dominate the affected side again across the midline. In addition, acupuncture stimulation induced improvement of axonal rewiring for corticospinal innervation is also possibly related to its functions in accelerating the synthesis and release of neurotrophic factors, down-regulating Nogo-A/RhoA signaling and activating vascular epithelial growth factor/Dll4/Notch signaling pathways.
Assuntos
Terapia por Acupuntura , Córtex Motor , Acidente Vascular Cerebral , Animais , Córtex Motor/metabolismo , Fatores de Crescimento Neural/metabolismo , Proteínas Nogo/metabolismo , Tratos Piramidais/metabolismo , Qualidade de Vida , Recuperação de Função Fisiológica/fisiologia , Acidente Vascular Cerebral/complicações , Acidente Vascular Cerebral/terapiaRESUMO
Spinal cord injury disrupts ascending and descending neural signals causing sensory and motor dysfunction. Neuromodulation with electrical stimulation is used in both clinical and research settings to induce neural plasticity and improve functional recovery following spinal trauma. However, the mechanisms by which electrical stimulation affects recovery remain unclear. In this study we examined the effects of cortical electrical stimulation following injury on transcription at several levels of the central nervous system. We performed a unilateral, incomplete cervical spinal contusion injury in rats and delivered stimulation for one week to the contralesional motor cortex to activate the corticospinal tract and other pathways. RNA was purified from bilateral subcortical white matter and 3 levels of the spinal cord. Here we provide the complete data set in the hope that it will be useful for researchers studying electrical stimulation as a therapy to improve recovery from the deficits associated with spinal cord injury.
Assuntos
Estimulação Elétrica , Tratos Piramidais/metabolismo , Traumatismos da Coluna Vertebral/genética , Transcriptoma , Substância Branca/metabolismo , Animais , Terapia por Estimulação Elétrica , Feminino , Plasticidade Neuronal , Ratos , Ratos Long-Evans , Traumatismos da Coluna Vertebral/terapiaRESUMO
BACKGROUND: Movement performance depends on the synaptic interactions generated by coherent parallel sensorimotor cortical outputs to different downstream targets. The major outputs of the neocortex to subcortical structures are driven by pyramidal tract neurons (PTNs) located in layer 5B. One of the main targets of PTNs is the spinal cord through the corticospinal (CS) system, which is formed by a complex collection of distinct CS circuits. However, little is known about intracortical synaptic interactions that originate CS commands and how different populations of CS neurons are functionally organized. To further understand the functional organization of the CS system, we analyzed the activity of unambiguously identified CS neurons projecting to different zones of the same spinal cord segment using two-photon calcium imaging and retrograde neuronal tracers. RESULTS: Sensorimotor cortex slices obtained from transgenic mice expressing GCaMP6 funder the Thy1 promoter were used to analyze the spontaneous calcium transients in layer 5 pyramidal neurons. Distinct subgroups of CS neurons projecting to dorsal horn and ventral areas of the same segment show more synchronous activity between them than with other subgroups. CONCLUSIONS: The results indicate that CS neurons projecting to different spinal cord zones segregated into functional ensembles depending on their hodology, suggesting that a modular organization of CS outputs controls sensorimotor behaviors in a coordinated manner.
Assuntos
Conectoma , Tratos Piramidais/fisiologia , Medula Espinal/fisiologia , Animais , Cálcio/metabolismo , Imunofluorescência/métodos , Camundongos , Camundongos Transgênicos , Córtex Motor/metabolismo , Córtex Motor/fisiologia , Vias Neurais/metabolismo , Vias Neurais/fisiologia , Técnicas de Rastreamento Neuroanatômico/métodos , Neurônios/fisiologia , Tratos Piramidais/metabolismo , Medula Espinal/metabolismoRESUMO
Activity in the mouse anterior lateral motor cortex (ALM) instructs directional movements, often seconds before movement initiation. It is unknown whether this preparatory activity is localized to ALM or widely distributed within motor cortex. Here we imaged activity across motor cortex while mice performed a whisker-based object localization task with a delayed, directional licking response. During tactile sensation and the delay epoch, object location was represented in motor cortex areas that are medial and posterior relative to ALM, including vibrissal motor cortex. Preparatory activity appeared first in deep layers of ALM, seconds before the behavioral response, and remained localized to ALM until the behavioral response. Later, widely distributed neurons represented the outcome of the trial. Cortical area was more predictive of neuronal selectivity than laminar location or axonal projection target. Motor cortex therefore represents sensory, motor, and outcome information in a spatially organized manner.
Assuntos
Comportamento Animal/fisiologia , Atividade Motora/fisiologia , Córtex Motor/fisiologia , Neurônios/fisiologia , Tato/fisiologia , Animais , Axônios , Cálcio/metabolismo , Tomada de Decisões , Processamento de Imagem Assistida por Computador , Camundongos , Córtex Motor/metabolismo , Imagem Óptica , Tratos Piramidais/metabolismo , Tratos Piramidais/fisiologia , VibrissasRESUMO
Canavan's disease (CD) is a hereditary leukodystrophy caused by mutations in the aspartoacylase gene (ASPA), leading to spongiform degeneration of the white matter and severe impairment of psychomotor development. We present the cases of two non-Jewish sisters with CD that have a milder and protracted clinical course compared to typical CD. MRI imaging revealed bilateral high-signal-intensity areas in the thalami and the internal capsule and MR spectroscopy showed typical findings for CD (a marked increase in N-acetylaspartate (NAA) levels). FA values of the right and left corticospinal tracts at the level of the posterior limb of the internal capsule, and the centrum semiovale were found to be significantly reduced compared to healthy controls. From a neurophysiological point of view, the peripheral motor system was normal. In contrast, cortical stimulation at maximal intensity failed to elicit facilitated or resting MEPs and silent periods (SPs) in upper and lower limbs, providing evidence for significant upper motor pathway dysfunction.
Assuntos
Doença de Canavan/diagnóstico por imagem , Doença de Canavan/terapia , Imagem de Tensor de Difusão/métodos , Vias Eferentes/diagnóstico por imagem , Estimulação Magnética Transcraniana/métodos , Adulto , Ácido Aspártico/análogos & derivados , Ácido Aspártico/metabolismo , Potencial Evocado Motor , Feminino , Humanos , Cápsula Interna/diagnóstico por imagem , Tratos Piramidais/diagnóstico por imagem , Tratos Piramidais/metabolismo , Irmãos , Tálamo/diagnóstico por imagemRESUMO
Activity-dependent changes of postsynaptic Ca2+-concentration are influenced by a variety of different Ca2+-channels and play an important role in synaptic plasticity. Paired associative stimulation (PAS) and theta-burst stimulation (TBS) are noninvasive magnetic stimulation protocols used in human subjects to induce lasting corticospinal excitability changes that have been likened to synaptic long-term potentiation and long-term depression. To better characterize the Ca2+-related physiological mechanisms underlying PAS- and TBS-induced plasticity, we examined the impact of different Ca2+-sources. PAS-induced facilitation of corticospinal excitability was blocked by NMDA-receptor blocker dextromethorphan (DXM) and L-type voltage gated Ca2+ channels (VGCC) blocker nimodipine (NDP), but turned into depression by T-type VGCC blocker ethosuximide (ESM). Although, surprisingly, static corticospinal excitability was increased by the combination of DXM and NDP, PAS-induced facilitation was blocked. TBS-induced facilitation of corticospinal excitability, which has previously been shown to be turned into depression by L-type VGCC blocker NDP (Wankerl K, Weise D, Gentner R, Rumpf J, Classen J. 2010. L-type voltage-gated Ca2+ channels: a single molecular switch for long-term potentiation/long-term depression-like plasticity and activity-dependent metaplasticity in humans. J Neurosci. 30(18):6197-6204.), was blocked, but not reverted, by T-type VGCC blocker ESM. The different patterns of Ca2+-channel modulation of PAS- and TBS-induced plasticity may point to an important role of backpropagating action potentials in PAS-induced plasticity, similar as in spike-timing dependent synaptic plasticity, and to a requirement of dendritic Ca2+-dependent spikes in TBS-induced plasticity.
Assuntos
Canais de Cálcio Tipo L/metabolismo , Canais de Cálcio Tipo T/metabolismo , Córtex Motor/fisiologia , Plasticidade Neuronal/fisiologia , Estimulação Magnética Transcraniana/métodos , Adolescente , Adulto , Bloqueadores dos Canais de Cálcio/farmacologia , Eletromiografia , Potencial Evocado Motor/efeitos dos fármacos , Potencial Evocado Motor/fisiologia , Antagonistas de Aminoácidos Excitatórios/farmacologia , Feminino , Mãos/fisiologia , Humanos , Masculino , Córtex Motor/efeitos dos fármacos , Músculo Esquelético/efeitos dos fármacos , Músculo Esquelético/fisiologia , Plasticidade Neuronal/efeitos dos fármacos , Tratos Piramidais/efeitos dos fármacos , Tratos Piramidais/metabolismo , Receptores de AMPA/antagonistas & inibidores , Receptores de AMPA/metabolismo , Adulto JovemRESUMO
Studies of axon regeneration in the spinal cord often assess regeneration of the corticospinal tract (CST). Emx1-Cre x Thy1-STOP-YFP mice have been reported to have yellow fluorescent protein (YFP) selectively expressed in forebrain neurons leading to genetic labeling of CST axons in the spinal cord, and it was suggested that these CST-YFP mice would be useful for studies of CST regeneration. Because regeneration past a lesion may involve only a few axons, the presence of labeled non-CST axons compromises interpretation. We show here that in CST-YFP mice, some YFP-labeled axons are not from the CST. Specifically, YFP-labeled axons are present in regions beyond those with anterogradely labeled CST axons, most YFP-labeled axons beyond established CST locations do not undergo Wallerian degeneration following a large lesion of the sensorimotor cortex, some rubrospinal and reticulospinal neurons are labeled with YFP, and some YFP-labeled cells in the spinal gray matter have YFP-labeled projections into the spinal cord white matter. We further demonstrate that the density of YFP-labeled axon arbors hinders tracing of single axons to their point of origin in the main descending tracts. In light of recent advances in 3D imaging for visualizing axons in unsectioned blocks of spinal cord, we also assessed CST-YFP mice for 3D imaging and found that YFP fluorescence in CST-YFP mice is faint for clearing-based 3D imaging in comparison with fluorescence in Thy1-YFP-H mice and fluorescence of mini-ruby biotinylated dextran amine (BDA). Overall, the nonspecific and faint YFP labeling in CST-YFP mice limits their utility for assessments of CST axon regeneration.
Assuntos
Regeneração Nervosa/fisiologia , Tratos Piramidais/metabolismo , Tratos Piramidais/fisiopatologia , Degeneração Walleriana/fisiopatologia , Animais , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Biotina/análogos & derivados , Biotina/metabolismo , Lesões Encefálicas/complicações , Lesões Encefálicas/patologia , Dextranos/metabolismo , Feminino , Lateralidade Funcional , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Imageamento Tridimensional , Proteínas Luminescentes/genética , Proteínas Luminescentes/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Microscopia Confocal , Córtex Motor/patologia , Neurônios/metabolismo , PTEN Fosfo-Hidrolase/genética , PTEN Fosfo-Hidrolase/metabolismo , Tratos Piramidais/patologia , Estilbamidinas/metabolismo , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Degeneração Walleriana/etiologiaRESUMO
Neuropathic pain is an important public health problem for which only a few treatments are available. Preclinical studies show that melatonin (MLT), a neurohormone acting on MT1 and MT2 receptors, has analgesic properties, likely through MT2 receptors. Here, we determined the effects of the novel selective MLT MT2 receptor partial agonist N-{2-([3-bromophenyl]-4-fluorophenylamino)ethyl}acetamide (UCM924) in 2 neuropathic pain models in rats and examined its supraspinal mechanism of action. In rat L5-L6 spinal nerve ligation and spared nerve injury models, UCM924 (20-40 mg/kg, subcutaneously) produced a prolonged antinociceptive effect that is : (1) dose-dependent and blocked by the selective MT2 receptor antagonist 4-phenyl-2-propionamidotetralin, (2) superior to a high dose of MLT (150 mg/kg) and comparable with gabapentin (100 mg/kg), but (3) without noticeable motor coordination impairments in the rotarod test. Using double staining immunohistochemistry, we found that MT2 receptors are expressed by glutamatergic neurons in the rostral ventrolateral periaqueductal gray. Using in vivo electrophysiology combined with tail flick, we observed that microinjection of UCM924 into the ventrolateral periaqueductal gray decreased tail flick responses, depressed the firing activity of ON cells, and activated the firing of OFF cells; all effects were MT2 receptor-dependent. Altogether, these data demonstrate that selective MT2 receptor partial agonists have analgesic properties through modulation of brainstem descending antinociceptive pathways, and MT2 receptors may represent a novel target in the treatment of neuropathic pain.
Assuntos
Acetamidas/metabolismo , Compostos de Anilina/metabolismo , Tronco Encefálico/metabolismo , Neuralgia/tratamento farmacológico , Neuralgia/metabolismo , Tratos Piramidais/metabolismo , Receptor MT2 de Melatonina/metabolismo , Acetamidas/farmacologia , Acetamidas/uso terapêutico , Compostos de Anilina/farmacologia , Compostos de Anilina/uso terapêutico , Animais , Tronco Encefálico/efeitos dos fármacos , Ligantes , Masculino , Medição da Dor/efeitos dos fármacos , Medição da Dor/métodos , Tratos Piramidais/efeitos dos fármacos , Ratos , Ratos Wistar , Receptor MT2 de Melatonina/agonistasRESUMO
PURPOSE: We aimed to assess, in amyotrophic lateral sclerosis (ALS), the diagnostic accuracy of the combined use of conventional MRI signal changes (namely, hypointensity of the precentral cortex and hyperintensity of the corticospinal tracts on T2-weighted images), and N-Acetyl-Aspartate (NAA) reduction in the motor cortex at Magnetic Resonance Spectroscopy (MRS), which are affected by limited diagnostic accuracy when used separately. METHODS: T2-hypointensity and NAA/(Choline+Creatine) ratio of the precentral gyrus and T2-hyperintensity of the corticospinal tracts were measured in 84 ALS patients and 28 healthy controls, using a Region-of-Interest approach. Sensitivity and specificity values were calculated using Fisher stepwise discriminant analysis, and cross-validated using the leave-one-out method. RESULTS: Precentral gyrus T2 signal intensity (p<10(-4)) and NAA peak (p<10(-6)) were significantly reduced in patients, and their values did not correlate significantly to each other both in patients and controls, while no significant differences were obtained in terms of T2-hyperintensity of the corticospinal tract. Sensitivity and specificity of the two discriminant variables, taken alone, were 71.4% and 75.0%, for NAA peak, and 63.1% and 71.4% for T2-hypointensity, respectively. When using these two variables in combination, a significant increase in sensitivity (78.6%) and specificity (82.1%) was achieved. CONCLUSIONS: Precentral gyrus T2-hypointensity and NAA peak are not significantly correlated in ALS patients, suggesting that they reflect relatively independent phenomena. The combined use of these measures improves the diagnostic accuracy of MRI in ALS diagnosis.
Assuntos
Esclerose Lateral Amiotrófica/diagnóstico , Córtex Cerebral/patologia , Imageamento por Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/métodos , Imagem Multimodal/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Esclerose Lateral Amiotrófica/metabolismo , Ácido Aspártico/análogos & derivados , Ácido Aspártico/metabolismo , Córtex Cerebral/metabolismo , Colina/metabolismo , Creatina/metabolismo , Feminino , Lobo Frontal/metabolismo , Lobo Frontal/patologia , Humanos , Masculino , Pessoa de Meia-Idade , Tratos Piramidais/metabolismo , Tratos Piramidais/patologia , Reprodutibilidade dos Testes , Estudos Retrospectivos , Sensibilidade e EspecificidadeRESUMO
The rapid decline of injury-induced neuronal circuit remodelling after birth is paralleled by the accumulation of chondroitin sulphate proteoglycans (CSPGs) in the extracellular matrix, culminating with the appearance of perineuronal nets (PNNs) around parvalbumin-expressing GABAergic interneurons. We used a spinal cord injury (SCI) model to study the interplay between integrity of PNN CSPGs in the sensorimotor cortex, anatomical remodelling of the corticospinal tract (CST) and motor recovery in adult mice. We showed that thoracic SCI resulted in an atrophy of GABAergic interneurons in the axotomized hindlimb cortex, as well as in a more widespread downregulation of parvalbumin expression. In parallel, spontaneous changes in the integrity of CSPG glycosaminoglycan (GAG) chains associated with PNNs occurred at the boundary between motor forelimb and sensorimotor hindlimb cortex, a region previously showed to undergo reorganization after thoracic SCI. Surprisingly, full digestion of CSPG GAG chains by intracortical chondroitinase ABC injection resulted in an aggravation of motor deficits and reduced sprouting of the axotomized CST above the lesion. Altogether, our data show that changes in the expression pattern of GABAergic markers and PNNs occur in regions of the sensorimotor cortex undergoing spontaneous reorganization after SCI, but suggest that these changes have to be tightly controlled to be of functional benefit.
Assuntos
Membro Posterior/inervação , Córtex Motor/fisiopatologia , Rede Nervosa/fisiopatologia , Plasticidade Neuronal , Tratos Piramidais/fisiopatologia , Córtex Sensório-Motor/fisiopatologia , Traumatismos da Medula Espinal/fisiopatologia , Animais , Biomarcadores/metabolismo , Proteoglicanas de Sulfatos de Condroitina/metabolismo , Modelos Animais de Doenças , Feminino , Neurônios GABAérgicos/metabolismo , Interneurônios/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Atividade Motora , Córtex Motor/metabolismo , Rede Nervosa/metabolismo , Tratos Piramidais/metabolismo , Recuperação de Função Fisiológica , Córtex Sensório-Motor/metabolismo , Traumatismos da Medula Espinal/metabolismo , Fatores de Tempo , Ácido gama-Aminobutírico/metabolismoRESUMO
Trans-spinal direct current (tsDC) stimulation is a modulator of spinal excitability and can influence cortically elicited muscle contraction in a polarity-dependent fashion. When combined with low-frequency repetitive cortical stimulation, cathodal tsDC [tsDC(-)] produces a long-term facilitation of cortically elicited muscle actions. We investigated the ability of this combined stimulation paradigm to facilitate cortically elicited muscle actions in spinal cord-injured and noninjured animals. The effect of tsDC-applied alone or in combination with repetitive spinal stimulation (rSS) on the release of the glutamate analog, D-2,3-(3)H-aspartate (D-Asp), from spinal cord preparations in vitro-was also tested. In noninjured animals, tsDC (-2 mA) reproducibly potentiated cortically elicited contractions of contralateral and ipsilateral muscles tested at various levels of baseline muscle contraction forces. Cortically elicited muscle responses in animals with contusive and hemisectioned spinal cord injuries (SCIs) were similarly potentiated. The combined paradigm of stimulation caused long-lasting potentiation of cortically elicited bilateral muscle contraction in injured and noninjured animals. Additional analysis suggests that at higher baseline forces, tsDC(-) application does not increase the rising slope of the muscle contraction but causes repeated firing of the same motor units. Both cathodal and anodal stimulations induced a significant increase of D-Asp release in vitro. The effect of the combined paradigm of stimulation (tsDC and rSS) on the concentration of extracellular D-Asp was polarity dependent. These results indicate that tsDC can powerfully modulate the responsiveness of spinal cord neurons. The results obtained from the in vitro preparation suggest that the changes in neuronal excitability were correlated with an increased concentration of extracellular glutamate. The combined paradigm of stimulation, used in our experiments, could be noninvasively applied to restore motor control in humans with SCI.
Assuntos
Ácido Aspártico/metabolismo , Córtex Cerebral/metabolismo , Terapia por Estimulação Elétrica/métodos , Potencial Evocado Motor , Ácido Glutâmico/metabolismo , Contração Muscular , Músculo Esquelético/inervação , Tratos Piramidais/metabolismo , Traumatismos da Medula Espinal/terapia , Animais , Ácido Aspártico/análogos & derivados , Comportamento Animal , Cálcio/metabolismo , Córtex Cerebral/fisiopatologia , Modelos Animais de Doenças , Feminino , Ácido Glutâmico/análogos & derivados , Potenciação de Longa Duração , Masculino , Camundongos , Atividade Motora , Força Muscular , Tratos Piramidais/fisiopatologia , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/fisiopatologia , Traumatismos da Medula Espinal/psicologia , Transmissão Sináptica , Fatores de TempoRESUMO
Transcription factors with gradients of expression in neocortical progenitors give rise to distinct motor and sensory cortical areas by controlling the area-specific differentiation of distinct neuronal subtypes. However, the molecular mechanisms underlying this area-restricted control are still unclear. Here, we show that COUP-TFI controls the timing of birth and specification of corticospinal motor neurons (CSMN) in somatosensory cortex via repression of a CSMN differentiation program. Loss of COUP-TFI function causes an area-specific premature generation of neurons with cardinal features of CSMN, which project to subcerebral structures, including the spinal cord. Concurrently, genuine CSMN differentiate imprecisely and do not project beyond the pons, together resulting in impaired skilled motor function in adult mice with cortical COUP-TFI loss-of-function. Our findings indicate that COUP-TFI exerts critical areal and temporal control over the precise differentiation of CSMN during corticogenesis, thereby enabling the area-specific functional features of motor and sensory areas to arise.
Assuntos
Fator I de Transcrição COUP/metabolismo , Regulação da Expressão Gênica no Desenvolvimento , Neurônios Motores/citologia , Neurogênese/genética , Tratos Piramidais/citologia , Lobo Temporal/crescimento & desenvolvimento , Animais , Fator I de Transcrição COUP/genética , Camundongos , Camundongos Knockout , Neurônios Motores/metabolismo , Tratos Piramidais/metabolismo , Lobo Temporal/metabolismo , Tálamo/crescimento & desenvolvimento , Tálamo/metabolismoRESUMO
Our objective was to characterize the structural and metabolic changes of the corticospinal tract (CST) in ALS patients using combined diffusion tensor imaging (DTI) and magnetic resonance spectroscopic imaging (MRSI). Fourteen patients (male:female, 6:8; mean age, 54 years) and 14 controls (male:female, 8:6; mean age, 53 years) underwent imaging. Four regions of the CST were evaluated: precentral gyrus, corona radiata, posterior limb of the internal capsule, and cerebral peduncle. DTI and MRSI indices tested included fractional anisotropy (FA), apparent diffusion coefficient (ADC), and the ratio of N-acetylaspartate to choline (NAA/Cho) and creatine (NAA/Cr). In the precentral gyrus, NAA/Cho was reduced 18% (p<0.001), NAA/Cr was reduced 9% (p=0.01), and FA was reduced 3% (p=0.02). NAA/Cho and NAA/Cr were reduced in the corona radiata (p<0.001). Reduced NAA/Cho in the precentral gyrus correlated with shorter symptom duration (r=0.66, p=0.02) and faster disease progression (r=-0.65, p=0.008). Increased spasticity correlated with higher ADC in the precentral gyrus (R=0.52, p=0.005). In conclusion, both MRSI and DTI provided in vivo evidence of intracranial degeneration of the CST in ALS that was most prominent rostrally in the precentral gyrus.
Assuntos
Esclerose Lateral Amiotrófica/metabolismo , Esclerose Lateral Amiotrófica/patologia , Imagem de Tensor de Difusão , Espectroscopia de Ressonância Magnética , Tratos Piramidais/metabolismo , Tratos Piramidais/patologia , Ácido Aspártico/análogos & derivados , Ácido Aspártico/metabolismo , Colina/metabolismo , Creatina/metabolismo , Progressão da Doença , Feminino , Humanos , Cápsula Interna/metabolismo , Cápsula Interna/patologia , Masculino , Pessoa de Meia-Idade , Córtex Motor/metabolismo , Córtex Motor/patologia , Curva ROC , Sensibilidade e EspecificidadeRESUMO
Chondroitin sulfate proteoglycans (CSPGs) inhibit axonal growth, and treatment with chondroitinase ABC promotes axonal regeneration in some models of central nervous system (CNS) injury. The aims of this study were (1) to compare the spatiotemporal appearance of CSPG expression between spinal cord contusion and hemisection models, and (2) to evaluate chondroitinase treatment effects on axonal regrowth in the two injury models. After hemisection, CSPG-immunoreactivity (IR) in the injury site rose to peak levels at 18 days but then decreased dramatically by 49 days; in contrast, CSPG-IR remained high for at least 49 days after contusion. After hemisection, many anterogradely labeled corticospinal tract (CST) axons remained close to CSPG-rich lesion sites, but after contusion, most CST axons retracted by approximately 1 mm rostral from the rostral-most CSPG-rich cyst. Intraspinal injection of chondroitinase at 0, 1, 2, and 4 weeks following injury dramatically reduced CSPG-IR in both injury models within 4 days, and CSPG-IR remained low for at least 3 weeks. After the chondroitinase treatment, many axons grew around the lesion site in hemisected spinal cords but not in contused spinal cords. We propose that improved axonal growth in hemisected spinal cords is due to decreased inhibition resulting from degradation of CSPGs located adjacent to severed CST axons. However, in spinal cord contusions, retracted CST axons fail to grow across gliotic regions that surround CSPG-rich injury sites despite efficient degradation with chondroitinase, suggesting that other inhibitors of axonal growth persist in the gliotic regions.
Assuntos
Axônios/fisiologia , Condroitina ABC Liase/administração & dosagem , Sulfatos de Condroitina/metabolismo , Regeneração Nervosa/fisiologia , Tratos Piramidais/fisiopatologia , Traumatismos da Medula Espinal/tratamento farmacológico , Animais , Relação Dose-Resposta a Droga , Feminino , Injeções Espinhais , Tratos Piramidais/metabolismo , Tratos Piramidais/patologia , Ratos , Ratos Sprague-Dawley , Traumatismos da Medula Espinal/metabolismo , Traumatismos da Medula Espinal/fisiopatologia , Fatores de TempoRESUMO
Fine movement in the body is controlled by the motor cortex, which signals in a topographically specific manner to neurons in the spinal cord by means of the corticospinal tract (CST). How the correct topography of the CST is established is unknown. To investigate the possibility that the Eph tyrosine kinase receptor EphA4 is involved in this process, we have traced CST axons in mice in which the EphA4 gene has been deleted. The forelimb subpopulation of CST axons is unaffected in the EphA4-/- mice, but the hindlimb subpopulation branches too early within the cord, both temporally and spatially. EphA4 shows a dynamic expression pattern in the environment of the developing CST in the spinal cord: high at the time of forelimb branching and down-regulated before hindlimb branching. To examine whether the fore- and hindlimb subpopulations of CST axons respond differently to EphA4 in their environment, neurons from fore- and hindlimb motor cortex were cultured on a substrate containing EphA4. Neurons from the hindlimb cortex showed reduced branching on the EphA4 substrate compared with their forelimb counterparts. Neurons from the hindlimb cortex express ephrinA5, a high-affinity ligand for EphA4, at higher levels compared with forelimb cortex neurons, and this expression is down-regulated before hindlimb branching. Together, these findings suggest that EphA4 regulates topographic mapping of the CST by controlling the branching of CST axons in the spinal cord.
Assuntos
Neurônios , Tratos Piramidais , Receptor EphA4/metabolismo , Animais , Animais Recém-Nascidos , Células Cultivadas , Membro Anterior/inervação , Membro Posterior/inervação , Humanos , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Córtex Motor/citologia , Córtex Motor/fisiologia , Neurônios/citologia , Neurônios/metabolismo , Tratos Piramidais/anatomia & histologia , Tratos Piramidais/crescimento & desenvolvimento , Tratos Piramidais/metabolismo , Receptor EphA4/genética , Medula Espinal/anatomia & histologia , Medula Espinal/crescimento & desenvolvimento , Medula Espinal/metabolismoRESUMO
Methylprednisolone (MP) is a synthetic glucocorticoid used for the treatment of spinal cord injury (SCI). Soluble Nogo-66 receptor (NgR) ectodomain is a novel experimental therapy for SCI that promotes axonal regeneration by blocking the growth inhibitory effects of myelin constituents in the adult central nervous system. To evaluate the potential complementarity of these mechanistically distinct pharmacological reagents we compared their effects alone and in combination after thoracic (T7) dorsal hemisection in the rat. Treatment with an ecto-domain of the rat NgR (27-310) fused to a rat IgG [NgR(310)ecto-Fc] (50 microm intrathecal, 0.25 microL/h for 28 days) or MP alone (30 mg/kg i.v., 0, 4 and 8 h postinjury) improved the rate and extent of functional recovery measured using Basso, Beattie, Bresnahan (BBB) scoring and footprint analysis. The effect of MP treatment on BBB score was apparent the day after SCI whereas the effect of NgR(310)ecto-Fc was not apparent until 2 weeks after SCI. NgR(310)ecto-Fc or MP treatment resulted in increased axonal sprouting and/or regeneration, quantified by counting biotin dextran amine-labeled corticospinal tract axons, and increased the number of axons contacting motor neurons in the ventral horn gray matter caudal to the lesion. Combined treatment with NgR(310)ecto-Fc and MP had a more pronounced effect on recovery of function and axonal growth compared with either treatment alone. The data demonstrate that NgR(310)ecto-Fc and MP act in a temporally and mechanistically distinct manner and suggest that they may have complementary effects.
Assuntos
Metilprednisolona/uso terapêutico , Receptores de Peptídeos/uso terapêutico , Traumatismos da Medula Espinal/tratamento farmacológico , Análise de Variância , Animais , Axônios/efeitos dos fármacos , Axônios/fisiologia , Comportamento Animal , Biotina/análogos & derivados , Biotina/metabolismo , Células Cultivadas , Embrião de Galinha , Dextranos/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Interações Medicamentosas , Quimioterapia Combinada , Comportamento Exploratório/efeitos dos fármacos , Feminino , Proteínas Ligadas por GPI , Gânglios Espinais/citologia , Imunoglobulina G/uso terapêutico , Laminectomia/métodos , Proteínas da Mielina , Bainha de Mielina/metabolismo , Regeneração Nervosa/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Receptor Nogo 1 , Tratos Piramidais/efeitos dos fármacos , Tratos Piramidais/metabolismo , Ratos , Ratos Long-Evans , Receptores de Superfície Celular , Receptores de Peptídeos/biossíntese , Receptores de Peptídeos/química , Receptores de Peptídeos/imunologia , Proteínas Recombinantes/uso terapêutico , Recuperação de Função Fisiológica/efeitos dos fármacos , Traumatismos da Medula Espinal/fisiopatologiaRESUMO
This study was conducted to investigate the metabolic changes in the motor and motor association cortices following axonal injury in the internal capsule that was caused by deep intracerebral hematoma. Using proton magnetic resonance spectroscopy (1H MRS), the authors studied the primary motor cortices (M-1) and supplementary motor areas (SMA) of 9 hemiparetic patients with documentable hemiparesis of varying severity, and we studied 10 normal volunteers as controls. To measure the M-1 and SMA biochemical changes, 4 separate single volumes of interest (VOIs) were located bilaterally in the affected and unaffected hemisphere (AH and UH). 1H MRS provided a neuronal and axonal viability index by measuring levels of N-acetylaspartate (NAA) and creatine/phosphocreatine (Cr). The M-1/SMA NAA/Cr ratios of the AH and UH in patients, and the AH and normal volunteers were compared. The NAA/Cr ratios of the M-1 and SMA in AH, and the SMA in UH were significantly lower than those of normal volunteers. These 1H MRS findings indicate that axonal injury in the descending motor pathway at the level of internal capsule could induce metabolic changes in the higher centers of the motor pathway.
Assuntos
Ácido Aspártico/análogos & derivados , Hemorragia dos Gânglios da Base/patologia , Espectroscopia de Ressonância Magnética , Córtex Motor/patologia , Paresia/patologia , Tratos Piramidais/patologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Ácido Aspártico/metabolismo , Hemorragia dos Gânglios da Base/metabolismo , Creatina/metabolismo , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Córtex Motor/metabolismo , Paresia/metabolismo , Fosfocreatina/metabolismo , Prótons , Tratos Piramidais/metabolismoRESUMO
This study was conducted to investigate the metabolic changes in the motor and motor association cortices following axonal injury in the internal capsule that was caused by deep intracerebral hematoma. Using proton magnetic resonance spectroscopy (1H MRS), the authors studied the primary motor cortices (M-1) and sup-plementary motor areas (SMA) of 9 hemiparetic patients with documentable hemi-paresis of varying severity, and we studied 10 normal volunteers as controls. To measure the M-1 and SMA biochemical changes, 4 separate single volumes of inter-est(VOIs) were located bilaterally in the affected and unaffected hemisphere (AH and UH).1H MRS provided a neuronal and axonal viability index by measuring levels of N-acetylaspartate (NAA) and creatine/phosphocreatine (Cr). The M-1/SMA NAA/Cr ratios of the AH and UH in patients, and the AH and normal volunteers were com-pared. The NAA/Cr ratios of the M-1 and SMA in AH, and the SMA in UH were sig-nificantly lower than those of normal volunteers. These 1H MRS findings indicate that axonal injury in the descending motor pathway at the level of internal capsule could induce metabolic changes in the higher centers of the motor pathway.
Assuntos
Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Ácido Aspártico/análogos & derivados , Hemorragia dos Gânglios da Base/metabolismo , Creatina/metabolismo , Espectroscopia de Ressonância Magnética , Córtex Motor/metabolismo , Paresia/metabolismo , Fosfocreatina/metabolismo , Prótons , Tratos Piramidais/metabolismoRESUMO
Spinal cord injury (SCI) results in loss of voluntary motor control followed by incomplete recovery, which is partly mediated by the descending corticospinal tract (CST). This system is an important target for therapeutic repair strategies after SCI; however, the question of whether apoptotic cell death occurs in these axotomized neurons remains unanswered. In this study, adult (150-175 g) male Sprague-Dawley rats underwent T9 transection of the dorsal funiculus, which axotomizes the dorsal CST, and introduction of the retrograde tracer Fluoro-Gold into the lesion site. Primary motor cortex (M1) was then examined for evidence of apoptosis weekly for 4 weeks after injury. Axotomized pyramidal cells, identified by retrograde transport of Fluoro-Gold, were found in M1 (57.5 +/- 9.6/median section, 6127 +/- 292 total), and a significant proportion were terminal deoxynucleotidyl transferase (TdT) -mediated deoxyuridine triphosphate (dUTP)-rhodamine nick end labeling (TUNEL) -positive at 1 week after injury (39.3 +/- 5.6%), compared with animals undergoing sham surgery (1.2 +/- 1.4%). At 2-4 weeks, fewer cells were Fluoro-Gold-positive (24.6 +/- 65.06 to 25.3 +/- 6.4/median section, 2338 +/- 233 to 2393 +/- 124 total), of which very few were TUNEL-positive. In TUNEL-positive cells, Hoechst 33342 staining revealed nuclear morphology consistent with apoptosis, chromatin condensation, and formation of apoptotic bodies. Fluoro-Gold-positive cells showed increased caspase-3 and Bax immunoreactivity. Hematoxylin and eosin staining revealed similar nuclear changes and dystrophic cells. Internucleosomal DNA fragmentation was detected by gel electrophoresis at the 1-week time point. Lesioned animals not receiving Fluoro-Gold exhibited the same markers of apoptosis. These results document, for the first time, features of apoptotic cell death in a proportion of axotomized cortical motor neurons after SCI, suggesting that protection from apoptosis may be a prerequisite for regenerative approaches to SCI.
Assuntos
Apoptose , Córtex Motor/patologia , Neurônios Motores/patologia , Proteínas Proto-Oncogênicas c-bcl-2 , Tratos Piramidais/patologia , Traumatismos da Medula Espinal/patologia , Animais , Axotomia , Caspase 3 , Caspases/metabolismo , Eletroforese em Gel de Ágar , Imuno-Histoquímica , Marcação In Situ das Extremidades Cortadas , Masculino , Córtex Motor/metabolismo , Neurônios Motores/metabolismo , Proteínas Proto-Oncogênicas/metabolismo , Tratos Piramidais/metabolismo , Ratos , Ratos Sprague-Dawley , Traumatismos da Medula Espinal/metabolismo , Proteína X Associada a bcl-2RESUMO
In order to study biological properties of the corticospinal tract, we have reconstructed this system in an in vitro slice culture preparation. Motor cortex and spinal cord slices, prepared from newborn rats, were co-cultured on pored membranes for 16-24 days. Anterograde labeling with biocytin showed that substantial neural connections had formed between the cortex and spinal cord slices. Retrograde labeling with horseradish peroxidase or 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate demonstrated that the parent cells were located primarily in the deeper layer of the cortex, as is found in vivo. Stimulation of the deep layer of the cortex elicited extracellular postsynaptic responses and intracellular excitatory postsynaptic potentials (EPSPs) in the co-cultured spinal cord that were mediated by the 1-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/ kainate-type glutamate receptor. The intracellular injection of biocytin after EPSPs were recorded showed that one-third of these cells were large stellate cells, which are thought to be motoneurons, while a large portion of the remaining labeled cells were bipolar cells of smaller sizes. Using this reconstructed in vitro preparation, we recorded field EPSPs (fEPSPs) along a 100-microm-interval lattice in the spinal gray matter, which allowed the quantitative evaluation of synapse formation. The fEPSP amplitudes were more than two-fold larger when the forelimb cortex was co-cultured with cervical cord rather than lumbar cord. However, hindlimb cortex did not show this preference. The fEPSP amplitudes were more than twice as large when the dorsal side of the spinal cord was adjacent to the cortex than the ventral side. In summary, we have reconstructed the corticospinal projection and synapses in vitro using cortical and spinal explants. This system allows for an efficient quantitative evaluation of synapse formation and for studies of postsynaptic cells. Our results suggest that synapse formation shows preferences along and perpendicular to the neuraxis of the spinal cord.