RESUMO
Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system's actual motor output - the activation of muscle fibers by motor neurons - typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices ('Myomatrix arrays') that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a 'motor unit,' during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system's motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and identifying pathologies of the motor system.
Assuntos
Neurônios Motores , Primatas , Ratos , Camundongos , Animais , Neurônios Motores/fisiologia , Eletrodos , Fibras Musculares EsqueléticasRESUMO
Neurons coordinate their activity to produce an astonishing variety of motor behaviors. Our present understanding of motor control has grown rapidly thanks to new methods for recording and analyzing populations of many individual neurons over time. In contrast, current methods for recording the nervous system's actual motor output - the activation of muscle fibers by motor neurons - typically cannot detect the individual electrical events produced by muscle fibers during natural behaviors and scale poorly across species and muscle groups. Here we present a novel class of electrode devices ("Myomatrix arrays") that record muscle activity at unprecedented resolution across muscles and behaviors. High-density, flexible electrode arrays allow for stable recordings from the muscle fibers activated by a single motor neuron, called a "motor unit", during natural behaviors in many species, including mice, rats, primates, songbirds, frogs, and insects. This technology therefore allows the nervous system's motor output to be monitored in unprecedented detail during complex behaviors across species and muscle morphologies. We anticipate that this technology will allow rapid advances in understanding the neural control of behavior and in identifying pathologies of the motor system.
RESUMO
V3 interneurons (INs) are a major group of excitatory commissural interneurons in the spinal cord, and they are essential for producing a stable and robust locomotor rhythm. V3 INs are generated from the ventral-most progenitor domain, p3, but migrate dorsally and laterally during postmitotic development. At birth, they are located in distinctive clusters in the ventral horn and deep dorsal horn. To assess the heterogeneity of this genetically identified group of spinal INs, we combined patch-clamp recording and anatomical tracing with cluster analysis. We examined electrophysiological and morphological properties of mature V3 INs identified by their expression of tdTomato fluorescent proteins in Sim1(Cre/+); Rosa(floxstop26TdTom) mice. We identified two V3 subpopulations with distinct intrinsic properties and spatial distribution patterns. Ventral V3 INs, primarily located in lamina VIII, possess a few branching processes and were capable of generating rapid tonic firing spikes. By contrast, dorsal V3 INs exhibited a more complex morphology and relatively slow average spike frequency with strong adaptation, and they also displayed large sag voltages and post-inhibitory rebound potentials. Our data suggested that hyperpolarization-activated cation channel currents and T-type calcium channel currents may account for some of the membrane properties of V3 INs. Finally, we observed that ventral and dorsal V3 INs were active in different ways during running and swimming, indicating that ventral V3 INs may act as premotor neurons and dorsal V3 INs as relay neurons mediating sensory inputs. Together, we detected two physiologically and topographically distinct subgroups of V3 INs, each likely playing different roles in locomotor activities.
Assuntos
Potenciais de Ação/fisiologia , Interneurônios/classificação , Interneurônios/fisiologia , Medula Espinal/citologia , Animais , Animais Recém-Nascidos , Fatores de Transcrição Hélice-Alça-Hélice Básicos/genética , Benzimidazóis/farmacologia , Fármacos Cardiovasculares/farmacologia , Análise por Conglomerados , Ciclopropanos/farmacologia , Estimulação Elétrica , Técnicas In Vitro , Camundongos , Camundongos Transgênicos , Atividade Motora/efeitos dos fármacos , Naftalenos/farmacologia , Níquel/farmacologia , Técnicas de Patch-Clamp , Proteínas Proto-Oncogênicas c-fos/farmacologia , Pirimidinas/farmacologia , RNA não Traduzido/genética , Proteínas Repressoras/genética , Estatísticas não ParamétricasRESUMO
Genetic strategies for perturbing activity of selected neurons hold great promise for understanding circuitry and behavior. Several such strategies exist, but there has been no direct demonstration of reversible inactivation of mammalian neurons in vivo. We previously reported quickly reversible inactivation of neurons in vitro using expression of the Drosophila allatostatin receptor (AlstR). Here, adeno-associated viral vectors are used to express AlstR in vivo in cortical and thalamic neurons of rats, ferrets, and monkeys. Application of the receptor's ligand, allatostatin (AL), leads to a dramatic reduction in neural activity, including responses of visual neurons to optimized visual stimuli. Additionally, AL eliminates activity in spinal cords of transgenic mice conditionally expressing AlstR. This reduction occurs selectively in AlstR-expressing neurons. Inactivation can be reversed within minutes upon washout of the ligand and is repeatable, demonstrating that the AlstR/AL system is effective for selective, quick, and reversible silencing of mammalian neurons in vivo.
Assuntos
Proteínas de Drosophila/fisiologia , Inibição Neural/fisiologia , Neurônios/metabolismo , Receptores Acoplados a Proteínas G/fisiologia , Receptores de Neuropeptídeos/fisiologia , Potenciais de Ação/fisiologia , Animais , Córtex Cerebral/metabolismo , Proteínas de Drosophila/biossíntese , Proteínas de Drosophila/genética , Feminino , Furões , Macaca mulatta , Masculino , Camundongos , Camundongos Transgênicos , Neuropeptídeos/metabolismo , Ratos , Receptores Acoplados a Proteínas G/biossíntese , Receptores Acoplados a Proteínas G/genética , Receptores de Neuropeptídeos/biossíntese , Receptores de Neuropeptídeos/genéticaRESUMO
The sequential stepping of left and right limbs is a fundamental motor behavior that underlies walking movements. This relatively simple locomotor behavior is generated by the rhythmic activity of motor neurons under the control of spinal neural networks known as central pattern generators (CPGs) that comprise multiple interneuron cell types. Little, however, is known about the identity and contribution of defined interneuronal populations to mammalian locomotor behaviors. We show a discrete subset of commissural spinal interneurons, whose fate is controlled by the activity of the homeobox gene Dbx1, has a critical role in controlling the left-right alternation of motor neurons innervating hindlimb muscles. Dbx1 mutant mice lacking these ventral interneurons exhibit an increased incidence of cobursting between left and right flexor/extensor motor neurons during drug-induced locomotion. Together, these findings identify Dbx1-dependent interneurons as key components of the spinal locomotor circuits that control stepping movements in mammals.
Assuntos
Interneurônios/metabolismo , Atividade Motora/genética , Medula Espinal/metabolismo , Caminhada/fisiologia , Animais , Genes fos/genética , Genes fos/fisiologia , Proteínas de Homeodomínio/biossíntese , Proteínas de Homeodomínio/genética , Técnicas In Vitro , Camundongos , Camundongos Mutantes , Atividade Motora/fisiologia , Desempenho Psicomotor/fisiologiaRESUMO
Glutamatergic and GABAergic neurons mediate much of the excitatory and inhibitory neurotransmission, respectively, in the vertebrate nervous system. The process by which developing neurons select between these two cell fates is poorly understood. Here we show that the homeobox genes Tlx3 and Tlx1 determine excitatory over inhibitory cell fates in the mouse dorsal spinal cord. First, we found that Tlx3 was required for specification of, and expressed in, glutamatergic neurons. Both generic and region-specific glutamatergic markers, including VGLUT2 and the AMPA receptor Gria2, were absent in Tlx mutant dorsal horn. Second, spinal GABAergic markers were derepressed in Tlx mutants, including Pax2 that is necessary for GABAergic differentiation, Gad1/2 and Viaat that regulate GABA synthesis and transport, and the kainate receptors Grik2/3. Third, ectopic expression of Tlx3 was sufficient to suppress GABAergic differentiation and induce formation of glutamatergic neurons. Finally, excess GABA-mediated inhibition caused dysfunction of central respiratory circuits in Tlx3 mutant mice.
Assuntos
Sistemas de Transporte de Aminoácidos , Diferenciação Celular/fisiologia , Ácido Glutâmico/metabolismo , Proteínas de Homeodomínio/fisiologia , Proteínas de Membrana Transportadoras , Neurônios/fisiologia , Proteínas de Transporte Vesicular , Ácido gama-Aminobutírico/metabolismo , Animais , Animais Recém-Nascidos , Bicuculina/farmacologia , Proteínas de Ligação ao Cálcio , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Contagem de Células/métodos , Diferenciação Celular/genética , Células Cultivadas , Embrião de Galinha , Proteínas de Ligação a DNA/deficiência , Proteínas de Ligação a DNA/genética , Eletroporação/métodos , Embrião de Mamíferos , Antagonistas GABAérgicos/farmacologia , Regulação da Expressão Gênica no Desenvolvimento , Glutamato Descarboxilase/metabolismo , Proteínas de Fluorescência Verde , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Imuno-Histoquímica/métodos , Hibridização In Situ/métodos , Peptídeos e Proteínas de Sinalização Intracelular , Isoenzimas/metabolismo , Proteínas com Homeodomínio LIM , Proteínas Luminescentes/metabolismo , Bulbo/citologia , Bulbo/embriologia , Bulbo/crescimento & desenvolvimento , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Knockout , Dados de Sequência Molecular , Fatores de Crescimento Neural/metabolismo , Inibição Neural/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Fator de Transcrição PAX2 , Técnicas de Patch-Clamp/métodos , Receptores de AMPA/genética , Receptores de AMPA/metabolismo , Receptores de Ácido Caínico/genética , Receptores de Ácido Caínico/metabolismo , Medula Espinal/citologia , Medula Espinal/embriologia , Medula Espinal/crescimento & desenvolvimento , Estatmina , Fatores de Transcrição/deficiência , Fatores de Transcrição/genética , Proteína Vesicular 2 de Transporte de Glutamato , Proteínas Vesiculares de Transporte de Aminoácidos InibidoresRESUMO
Association and relay neurons that are generated in the dorsal spinal cord play essential roles in transducing somatosensory information. During development, these two major neuronal classes are delineated by the expression of the homeodomain transcription factor Lbx1. Lbx1 is expressed in and required for the correct specification of three early dorsal interneuron populations and late-born neurons that form the substantia gelatinosa. In mice lacking Lbx1, cells types that arise in the ventral alar plate acquire more dorsal identities. This results in the loss of dorsal horn association interneurons, excess production of commissural neurons, and disrupted sensory afferent innervation of the dorsal horn. Lbx1, therefore, plays a critical role in the development of sensory pathways in the spinal cord that relay pain and touch.