RESUMO
The aim of research is to unveil the mechanisms of the beneficial effects of XYD on PCIV in a rabbit model. 40 New Zealand white rabbits were randomly divided into 5 groups,including normal control group (NC), model control group (MC), low-dose of XYD group (LXYD), high-dose of XYD group (HXYD) and Yang-Xue-Qin-Nao group (YXQN). PCIV rabbit model was established by feeding high-fat diet companied with paravertebral sclerotherapy and rotation exercise. The general observation, step-down test, rheoencephalogram, blood tests, histopathological detection and the plasma concentration of the effective component of XYD were investigated. After pharmacological intervening, the step-down time, REG, PL, IPL, blood viscosity, the levels of blood lipids, CRGP were significantly improved. Moreover, the vertebral artery showed the reduced stenosis of arterial lumen and less proliferation of fibrous tissue in the arterial wall in the LXYD, HXYD and YXQN group. Based on the LC-MS detection, the blood concentrations of puerarin in the LXYD and HXYD group were significantly increased after pharmacological intervening. XYD could ameliorate the symptoms of vertigo, Qi-deficiency and blood stasis in PCIV rabbits via effectively regulating the levels of blood lipids and vasoactive substances, decreasing blood viscosity, increasing CBF and protecting vestibular function.
Assuntos
Comportamento Animal/efeitos dos fármacos , Medicamentos de Ervas Chinesas/farmacologia , Potenciais Evocados Auditivos do Tronco Encefálico/efeitos dos fármacos , Artéria Vertebral/efeitos dos fármacos , Insuficiência Vertebrobasilar/fisiopatologia , Vertigem/fisiopatologia , Núcleos Vestibulares/efeitos dos fármacos , Animais , Modelos Animais de Doenças , Hemorreologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Medicina Tradicional Chinesa , Coelhos , Artéria Vertebral/patologia , Artéria Vertebral/ultraestrutura , Núcleos Vestibulares/patologia , Núcleos Vestibulares/ultraestruturaRESUMO
As sensory information moves through the brain, higher-order areas exhibit more complex tuning than lower areas. Though models predict that complexity arises via convergent inputs from neurons with diverse response properties, in most vertebrate systems, convergence has only been inferred rather than tested directly. Here, we measure sensory computations in zebrafish vestibular neurons across multiple axes in vivo. We establish that whole-cell physiological recordings reveal tuning of individual vestibular afferent inputs and their postsynaptic targets. Strong, sparse synaptic inputs can be distinguished by their amplitudes, permitting analysis of afferent convergence in vivo. An independent approach, serial-section electron microscopy, supports the inferred connectivity. We find that afferents with similar or differing preferred directions converge on central vestibular neurons, conferring more simple or complex tuning, respectively. Together, these results provide a direct, quantifiable demonstration of feedforward input convergence in vivo.
Assuntos
Neurônios Aferentes/fisiologia , Membrana dos Otólitos/fisiologia , Núcleos Vestibulares/fisiologia , Animais , Estimulação Elétrica , Potenciais Somatossensoriais Evocados/fisiologia , Técnicas de Introdução de Genes , Microscopia Eletrônica , Neurônios/fisiologia , Neurônios/ultraestrutura , Neurônios Aferentes/ultraestrutura , Núcleos Vestibulares/ultraestrutura , Peixe-ZebraRESUMO
During sinusoidal rotation or translation, primary vestibular afferents modulate their discharge rates at the frequency of motion, effectively transmitting frequency-modulated (FM) signals. This study indicates a possible role for excitatory synapses in the processing of FM signals by vestibular brainstem pathways. Inputs to medial vestibular neurons were activated with FM pulse trains, while inhibitory transmission was blocked. The relationship between the presynaptic pulse rate and the postsynaptic membrane potential was found to be linear within a range of pulse rates. Short-term plasticity was a factor contributing to sensitivity at higher modulating frequencies. The amount of low-pass filtering was correlated with excitatory postsynaptic potential (EPSP) shape, which affected temporal summation during the train. Although the NMDA component of glutamatergic transmission affected EPSP shape, it made only a minor contribution to the dynamics of synaptic transmission. Most responses showed low-pass filtering over the entire 1-16 Hz range. Overall, excitatory synapses in the medial vestibular nucleus contribute a low-pass filter to central vestibular processing and complement the high-pass filtering that is introduced both by peripheral vestibular dynamics and by the intrinsic dynamics of secondary vestibular neurons.
Assuntos
Ácido Glutâmico/metabolismo , Plasticidade Neuronal/fisiologia , Terminações Pré-Sinápticas/fisiologia , Sinapses/fisiologia , Núcleos Vestibulares/fisiologia , Animais , Animais Recém-Nascidos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Feminino , Movimentos da Cabeça/fisiologia , Potenciais Pós-Sinápticos Inibidores/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Percepção de Movimento/fisiologia , Equilíbrio Postural/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Desempenho Psicomotor/fisiologia , Reflexo Vestíbulo-Ocular/fisiologia , Ductos Semicirculares/fisiologia , Sinapses/ultraestrutura , Transmissão Sináptica/fisiologia , Núcleos Vestibulares/ultraestrutura , Vestíbulo do Labirinto/fisiologiaRESUMO
Phaseolus vulgaris leucoagglutinin (PHA-L) was injected into the individual vestibular nuclei of the rat to study their efferent connections. One of the major differences between the connections of these nuclei was found at the level of the mesencephalon: the eye-moving cranial nerve nuclei received the densest projection from the superior vestibular nucleus (SVN). In the present electron microscopic study, we have found that terminals of SVN origin established symmetric synaptic contacts in the oculomotor nucleus. More than two-thirds of PHA-L-labeled boutons terminated on dendrites, the rest of them established axosomatic contacts. Most of the labeled terminals were GABA-positive, supporting the results of previous physiological experiments, which showed inhibitory effects. In the mesencephalon, the other termination area was found in the red nucleus. The PHA-L-labeled boutons of SVN origin were in close contact with the perikarya and proximal dendrites of the magnocellular part of the red nucleus. The types of synaptic contacts and distribution of terminals of SVN origin were similar to those found in the oculomotor nucleus. Our results indicate that the SVN can modify the activity of the cerebellorubral and corticorubral pathways, exerting inhibitory action on the neurons of the red nucleus.
Assuntos
Vias Eferentes/ultraestrutura , Nervo Oculomotor/fisiologia , Núcleo Rubro/ultraestrutura , Núcleos Vestibulares/ultraestrutura , Animais , Microscopia Eletrônica , Microscopia Imunoeletrônica/métodos , Fito-Hemaglutininas/metabolismo , Ratos , Ratos Wistar , Núcleo Rubro/metabolismo , Núcleos Vestibulares/metabolismo , Ácido gama-Aminobutírico/metabolismoRESUMO
We hypothesized that peripheral vestibular disorders might affect mitochondria in the vestibular nucleus complex (VNC). We tested this using unilateral labyrinthectomy (UL) as a model for the effects of vestibular damage on the VNC and used Western blotting and electron microscopy to analyze mitochondria. In rats receiving UL we did not find any changes in mitochondrial ultrastructure in the medial vestibular nucleus following UL, and there was no change in the expression or activation of the apoptosis effector caspase-3 in the whole VNC following UL. However, we did detect a small but statistically significant upregulation of the anti-apoptotic protein Bcl-2 in the contralateral VNC at 10 h post-UL.
Assuntos
Apoptose/fisiologia , Regulação da Expressão Gênica/fisiologia , Doenças do Labirinto/metabolismo , Mitocôndrias/ultraestrutura , Neurônios/metabolismo , Núcleos Vestibulares/patologia , Animais , Western Blotting/métodos , Caspase 3 , Caspases/metabolismo , Orelha Interna/cirurgia , Lateralidade Funcional/fisiologia , Imuno-Histoquímica/métodos , Doenças do Labirinto/etiologia , Doenças do Labirinto/patologia , Masculino , Microscopia Eletrônica de Transmissão/métodos , Neurônios/ultraestrutura , Ratos , Ratos Wistar , Fatores de Tempo , Núcleos Vestibulares/metabolismo , Núcleos Vestibulares/ultraestruturaRESUMO
The effects of high frequency stimulation (HFS) of the primary vestibular afferents on synaptic transmission in the ventral part of the medial vestibular nuclei (vMVN) were studied during postnatal development and compared with the changes in the expression of the group I metabotropic glutamate receptor (mGluR) subtypes, mGluR1 and mGluR5. During the first stages of development, HFS always induced a mGluR5- and GABAA-dependent long-term depression (LTD) which did not require NMDA receptor and mGluR1 activation. The probability of inducing LTD decreased progressively throughout the development and it was zero at about the end of the second postnatal week. Conversely, long-term potentiation (LTP) appeared at the beginning of the second week and its occurrence increased to reach the adult value at the end of the third week. Of interest, the sudden change in the LTP frequency occurred at the time of eye opening, about the end of the second postnatal week. LTP depended on NMDA receptor and mGluR1 activation. In parallel with the modifications in synaptic plasticity, we observed that the expression patterns and localizations of mGluR5 and mGluR1 in the medial vestibular nuclei (MVN) changed during postnatal development. At the earlier stages the mGluR1 expression was minimal, then increased progressively. In contrast, mGluR5 expression was initially high, then decreased. While mGluR1 was exclusively localized in neuronal compartments and concentrated at the postsynaptic sites at all stages observed, mGluR5 was found mainly in neuronal compartments at immature stages, then preferentially in glial compartments at mature stages. These results provide the first evidence for a progressive change from LTD to LTP accompanied by a distinct maturation expression of mGluR1 and mGluR5 during the development of the MVN.
Assuntos
Potenciação de Longa Duração/fisiologia , Depressão Sináptica de Longo Prazo/fisiologia , Receptores de Glutamato Metabotrópico/fisiologia , Núcleos Vestibulares/fisiologia , 2-Amino-5-fosfonovalerato/farmacologia , Fatores Etários , Animais , Bicuculina/farmacologia , Western Blotting , Cromonas/farmacologia , Estimulação Elétrica , Eletrofisiologia , Antagonistas de Receptores de GABA-A , Regulação da Expressão Gênica no Desenvolvimento , Imuno-Histoquímica , Hibridização In Situ , Potenciação de Longa Duração/efeitos dos fármacos , Depressão Sináptica de Longo Prazo/efeitos dos fármacos , Microscopia Confocal , Microscopia Imunoeletrônica , Piridinas/farmacologia , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Receptor de Glutamato Metabotrópico 5 , Receptores de GABA-A/fisiologia , Receptores de Glutamato Metabotrópico/antagonistas & inibidores , Receptores de Glutamato Metabotrópico/genética , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/fisiologia , Núcleos Vestibulares/crescimento & desenvolvimento , Núcleos Vestibulares/ultraestruturaRESUMO
The cellular and subcellular localization of L-citrulline was analyzed in the adult rat brain and compared with that of traditional markers for the presence of nitric oxide synthase. Light, transmission electron, and confocal laser scanning microscopy were used to study tissue sections processed for immunocytochemistry employing a monoclonal antibody against L-citrulline or polyclonal anti-neuronal nitric oxide synthase sera, and double immunofluorescence to detect neuronal nitric oxide synthase and L-citrulline co-localization. The results demonstrate that the same CNS regions and cell types are labeled by neuronal nitric oxide synthase polyclonal antisera and L-citrulline monoclonal antibodies, using both immunocytochemistry and immunofluorescence. Short-term pretreatment with a nitric oxide synthase inhibitor reduces L-citrulline immunostaining, but does not affect neuronal nitric oxide synthase immunoreactivity. In the vestibular brainstem, double immunofluorescence studies show that many, but not all, neuronal nitric oxide synthase-positive cells co-express L-citrulline, and that local intracellular patches of intense L-citrulline accumulation are present in some neurons. Conversely, all L-citrulline-labeled neurons co-express neuronal nitric oxide synthase. Cells expressing neuronal nitric oxide synthase alone are interpreted as neurons with the potential to produce nitric oxide under other stimulus conditions, and the subcellular foci of enhanced L-citrulline staining are viewed as intracellular sites of nitric oxide production. This interpretation is supported by ultrastructural observations of subcellular foci with enhanced L-citrulline and/or neuronal nitric oxide synthase staining that are located primarily at postsynaptic densities and portions of the endoplasmic reticulum. We conclude that nitric oxide is produced and released at focal sites within neurons that are identifiable using L-citrulline as a marker.
Assuntos
Compartimento Celular/fisiologia , Citrulina/metabolismo , Neurônios Nitrérgicos/metabolismo , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico/biossíntese , Núcleos Vestibulares/metabolismo , Animais , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Inibidores Enzimáticos/farmacologia , Imunofluorescência , Masculino , Microscopia Eletrônica , NG-Nitroarginina Metil Éster/farmacologia , Neurônios Nitrérgicos/ultraestrutura , Ratos , Ratos Sprague-Dawley , Membranas Sinápticas/metabolismo , Membranas Sinápticas/ultraestrutura , Núcleos Vestibulares/ultraestruturaRESUMO
The tangential nucleus is a major part of the avian vestibular nuclear complex, and its principal cells are structurally distinctive neurons participating in the vestibuloocular and vestibulocollic reflexes. After unilateral peripheral vestibular lesion, a behavioral recovery of function defined as vestibular compensation is observed. Because sprouting and hypertrophy of synapses have been reported in other regions of immature animals after central nervous system injury, we investigated whether this also occurs in the vestibular nuclei during compensation. To test this hypothesis, unilateral vestibular ganglionectomy was performed on 4-6-day-old hatchlings and vestibular function was tested during the next 2 months. Degeneration and evidence for regeneration of synapses were studied in the tangential nucleus at 1, 3, 7, and 56 days after surgery. Spoon endings, large vestibular terminals on the principal somata, degenerated 1-3 days after surgery. However, the small synaptic terminals showed no significant change in the percentage or number covering the soma or in mean terminal lengths in the deafferented or contralateral tangential nucleus. Furthermore, there was no evidence of neuron death in the tangential nucleus. Vestibular compensation occurred in three stages: 0-3 days, when vestibular synapses degenerated and severe behavioral deficits were seen; 4-9 days, when primary vestibular fibers degenerated centrally and marked improvement in both the static and the dynamic symptoms were observed; and 10-56 days, when changes in neuronal morphology were not detected but the dynamic symptoms gradually improved. Accordingly, after unilateral vestibular ganglionectomy, vestibular compensation proceeded without ultrastructural evidence of sprouting or hypertrophy of axosomatic synapses in the hatchling tangential nucleus. This rapid behavioral recovery of function distinguishes the vestibular system from other sensory systems, which, in general, exhibit much less robust recovery after injury to their peripheral receptors.
Assuntos
Adaptação Fisiológica/fisiologia , Galinhas/crescimento & desenvolvimento , Regeneração Nervosa/fisiologia , Plasticidade Neuronal/fisiologia , Terminações Pré-Sinápticas/ultraestrutura , Recuperação de Função Fisiológica/fisiologia , Núcleos Vestibulares/crescimento & desenvolvimento , Núcleos Vestibulares/ultraestrutura , Animais , Animais Recém-Nascidos , Comportamento Animal/fisiologia , Contagem de Células , Galinhas/anatomia & histologia , Galinhas/metabolismo , Denervação , Transtornos Neurológicos da Marcha/etiologia , Transtornos Neurológicos da Marcha/patologia , Transtornos Neurológicos da Marcha/fisiopatologia , Microscopia Eletrônica , Modelos Biológicos , Neurônios Aferentes/patologia , Neurônios Aferentes/ultraestrutura , Equilíbrio Postural/fisiologia , Postura/fisiologia , Terminações Pré-Sinápticas/patologia , Reflexo/fisiologia , Sinapses/patologia , Sinapses/ultraestrutura , Fatores de Tempo , Nervo Vestibular/lesões , Nervo Vestibular/patologia , Nervo Vestibular/fisiopatologia , Nervo Vestibular/cirurgia , Nervo Vestibular/ultraestrutura , Núcleos Vestibulares/patologia , Vestíbulo do Labirinto/fisiopatologia , Degeneração Walleriana/patologia , Degeneração Walleriana/fisiopatologiaRESUMO
Synapse counting was undertaken by conventional electron microscopy in primary vestibular integration centers (i.e., Nucleus descendens, Nd, and Nucleus magnocellularis, Nm, of the brainstem Area octavolateralis) and in the diencephalic visual Nucleus corticalis (Nc) of spaceflown neonate swordtail fish Xiphophorus helleri as well as in 1 g control siblings. Spaceflight (16 days microgravity, STS-90 Neurolab-Mission) yielded an increase in synaptic contacts only within the vestibular Nd indicating that lack of input resulted in compensation processes. No effect of microgravity, however, was observed in the visual Nc and in the vestibular Nm which is situated in the close vicinity of the Nd. In contrast to the latter, the Nm does not receive exclusively vestibular input, but inputs from the lateral line as well, possibly providing sufficient input at microgravity.
Assuntos
Ciprinodontiformes/fisiologia , Plasticidade Neuronal/fisiologia , Voo Espacial , Sinapses/ultraestrutura , Núcleos Vestibulares/ultraestrutura , Ausência de Peso , Adaptação Fisiológica , Animais , Animais Recém-Nascidos , Tronco Encefálico/fisiologia , Tronco Encefálico/ultraestrutura , Ciprinodontiformes/anatomia & histologia , Microscopia Eletrônica , Neurópilo/fisiologia , Neurópilo/ultraestrutura , Sinapses/fisiologia , Núcleos Vestibulares/fisiologiaRESUMO
The unipolar brush cell (UBC), a small interneuron occurring at high density in the granular layer of the mammalian vestibulocerebellum, receives a giant glutamatergic synapse from a single mossy fiber (MF) rosette, usually on a brush of dendritic branchlets. MF stimulation produces a current in the UBC several orders of magnitude greater in duration than at other glutamatergic synapses. We assumed that the cytoskeleton would have a special role in plasticity of the MF-UBC synapse. Neurofilaments and microtubules are enriched in the UBC somatodendritic compartment but are conspicuously absent in close proximity to the giant synapse, where standard electron microscopy reveals a granulo-flocculent material. Because osmium tetroxide fixation during sample preparation for standard electron microscopy destabilizes actin filaments, we hypothesized that this subsynaptic granulo-flocculent material is actin-based. After actin stabilization, we observed prominent, but loosely organized, bundles of microfilaments at the subsynaptic region of the MF-UBC synapse that linked the postsynaptic density with the cytoskeletal core of the dendritic branchlets. Confocal fluorescence microscopy and pre- and postembedding immunogold labeling with phalloidin and actin antibodies showed that these microfilaments consist of f-actin and contain little beta-actin. This extraordinary postsynaptic actin apparatus is ideally situated to form a dynamic framework for glutamate receptors and other postsynaptic molecules, and to mediate activity-dependent plastic rearrangements of the giant synapse.
Assuntos
Citoesqueleto de Actina/fisiologia , Cerebelo/fisiologia , Interneurônios/fisiologia , Fibras Nervosas/fisiologia , Sinapses/fisiologia , Núcleos Vestibulares/fisiologia , Citoesqueleto de Actina/ultraestrutura , Animais , Cerebelo/citologia , Cerebelo/ultraestrutura , Imunofluorescência , Interneurônios/ultraestrutura , Microscopia Confocal , Microscopia Eletrônica , Microscopia Imunoeletrônica , Subfragmentos de Miosina , Fibras Nervosas/ultraestrutura , Coelhos , Ratos , Ratos Sprague-Dawley , Sinapses/ultraestrutura , Núcleos Vestibulares/citologia , Núcleos Vestibulares/ultraestruturaRESUMO
We investigated membrane electrophysiological features of dissociated vestibular ganglion neurons, using a voltage-sensitive dye and a multiple site optical imaging system. The neuronal nature of the cultured vestibular ganglion cells was confirmed by positive staining with the anti-neurofilament 200 kDa antibody, using immunocytochemical methods. Optical absorption of the dye which binds to the external surface of neuron membranes increased while the cells were depolarized during perfusion with 150 mM potassium solution. The relative ratio (deltaI/I) of optical absorption change was 0.23 +/- 0.08% (means +/- S.D., n = 16). These optical responses were wavelength dependent, therefore, the optical response apparently originated from the voltage-sensitive dye. Under our experimental conditions, photodynamic damage and pharmacological effects of the dye were either absent or insignificant. We therefore concluded that optical recording is a new, practical and non-invasive method to simultaneously monitor changes in membrane potential from cultured vestibular ganglion cells. Optical recording is expected to provide further insight into mechanisms of information processing by vestibular ganglion neurons.
Assuntos
Gânglios Sensitivos/ultraestrutura , Óptica e Fotônica/instrumentação , Núcleos Vestibulares/ultraestrutura , Vestíbulo do Labirinto/fisiologia , Absorção , Animais , Animais Recém-Nascidos , Anticorpos/metabolismo , Membrana Celular/ultraestrutura , Células Cultivadas , Corantes/farmacocinética , Gânglios Sensitivos/metabolismo , Imuno-Histoquímica , Potenciais da Membrana/fisiologia , Camundongos , Camundongos Endogâmicos ICR , Proteínas de Neurofilamentos/metabolismo , Técnicas de Patch-Clamp , Núcleos Vestibulares/metabolismoRESUMO
The purpose of the present study was to detail the spinal cord (SC) trajectories and arborization patterns of vestibulospinal axons descending from the lateral vestibular nucleus (LVN). An anterograde neural tracer, Phaseolus vulgaris-leucoagglutinin (PHA-L), was focally injected into the right-side LVN in 8 cats. Their subsequent survival times varied from 4 days to 12 weeks. The labeled axons were found mainly in the brainstem after 4-5 days and in successively more caudal spinal segments after longer survival times: i.e., in C1-T2 after 2-3 weeks, in C3-T11 after 6-7 weeks, and in T7-S1 after 10-12 weeks. The trajectories of 28 single, thick (diameter >/=2.4 microm) lateral vestibulospinal tract (LVST) axons were traced from serial transverse sections of the SC from C1-8 (n = 10), T1-9 (n = 11), and T11-L7 (n = 7). In the cervical segments, the LVST axons gave off collateral fibers, which terminated mainly in Rexed's laminae VII-VIII. The terminal-field patterns of these collaterals differed from one stem axon to another. In the thoracic segments, the terminal-field patterns from a given LVST axon were similar at each segmental level, i.e., a few main branches with or without short side branches. At the L3-5 midlumbar level, the collaterals usually arborized more extensively, such that their terminal fields occupied a much greater region of laminae VII-VIII. In contrast, at the L6-7 lower lumbar level, collaterals arising from thin axons (diameter <1.0 microm) tended to innervate, with even more extensive arborization, the medial part of the lamina VIII. These results revealed common and segment-specific collateral distribution patterns of LVST axons along the full extent of the spinal neuraxis.
Assuntos
Axônios/fisiologia , Mapeamento Encefálico/métodos , Gatos/fisiologia , Medula Espinal/fisiologia , Núcleos Vestibulares/fisiologia , Animais , Tronco Encefálico/fisiologia , Feminino , Região Lombossacral , Masculino , Pescoço/inervação , Fito-Hemaglutininas , Medula Espinal/ultraestrutura , Taxa de Sobrevida , Tórax/inervação , Núcleos Vestibulares/ultraestruturaRESUMO
The ultrastructural characteristics of non-degenerating GABAergic neurons in rostrolateral medial vestibular nucleus were identified in monkeys following midline transection of vestibular commissural fibers. In the previous papers, we reported that most degenerated cells and terminals in this tissue were located in rostrolateral medial vestibular nucleus, and that many of these neurons were GABA-immunoreactive. In the present study, we examined the ultrastructural features of the remaining neuronal elements in this medial vestibular nucleus region, in order to identify and characterize the GABAergic cells that are not directly involved in the vestibular commissural pathway related to the velocity storage mechanism. Such cells are primarily small, with centrally-placed nuclei. Axosomatic synapses are concentrated on polar regions of the somata. The proximal dendrites of GABAergic cells are surrounded by boutons, although distal dendrites receive only occasional synaptic contacts. Two types of non-degenerated GABAergic boutons are distinguished. Type A terminals are large, with very densely-packed spherical synaptic vesicles and clusters of large, irregularly-shaped mitochondria with wide matrix spaces. Such boutons form symmetric synapses, primarily with small GABAergic and non-GABAergic dendrites. Type B terminals are smaller and contain a moderate density of round/pleomorphic vesicles, numerous small round or tubular mitochondria, cisterns and vacuoles. These boutons serve both pre- and postsynaptic roles in symmetric contacts with non-GABAergic axon terminals. On the basis of ultrastructural observations of immunostained tissue, we conclude that at least two types of GABAergic neurons are present in the rostrolateral portion of the monkey medial vestibular nucleus: neurons related to the velocity storage pathway, and a class of vestibular interneurons. A multiplicity of GABAergic bouton types are also observed, and categorized on the basis of subcellular morphology. We hypothesize that "Type A" boutons correspond to Purkinje cell afferents in rostrolateral medial vestibular nucleus, "Type B" terminals represent the axons of GABAergic medial vestibular nucleus interneurons, and "Type C" boutons take origin from vestibular commissural neurons of the velocity storage pathway.
Assuntos
Neurônios/ultraestrutura , Núcleos Vestibulares/ultraestrutura , Ácido gama-Aminobutírico/fisiologia , Animais , Axônios/fisiologia , Axônios/ultraestrutura , Dendritos/fisiologia , Dendritos/ultraestrutura , Macaca fascicularis , Macaca mulatta , Microscopia Eletrônica , Degeneração Neural/fisiopatologia , Fibras Nervosas/fisiologia , Fibras Nervosas Mielinizadas/fisiologia , Fibras Nervosas Mielinizadas/ultraestrutura , Neurônios/fisiologia , Núcleos Vestibulares/fisiologia , Vias Visuais/fisiologia , Vias Visuais/ultraestruturaRESUMO
Spinal respiratory motoneuron activity is controlled primarily by excitatory and inhibitory neurons in the medulla oblongata. To identify bulbospinal inhibitory neurons, immunohistochemistry for glutamic acid decarboxylase (GAD) was combined with retrograde labeling of projections to the C(4) ventral horn with Fluoro-Gold. GAD-immunoreactive bulbospinal neurons were located in the ventrolateral portion of the intermediate reticular nucleus, the ventral portion of the medial reticular nuclei, and the raphe and spinal vestibular nuclei. Small numbers of bulbospinal ventral respiratory group neurons were GAD immunoreactive. These neurons were distributed throughout the rostral ventral respiratory group and the Bötzinger complex. Surprisingly, low numbers of Bötzinger neurons, a population thought to be exclusively inhibitory, were GAD immunoreactive. These results suggest that the rostral ventral respiratory group and the Bötzinger complex both contain heterogeneous bulbospinal neuron populations, only some of which have gamma-aminobutyric acid (GABA)-mediated inhibitory control over phrenic motoneurons. Furthermore, the ventral respiratory group contained many GABAergic neurons that lacked bulbospinal projections.
Assuntos
Glutamato Descarboxilase/análise , Proteínas do Tecido Nervoso/análise , Neurônios/metabolismo , Centro Respiratório/citologia , Músculos Respiratórios/inervação , Medula Espinal/citologia , Estilbamidinas , Ácido gama-Aminobutírico/biossíntese , Animais , Colchicina , Corantes Fluorescentes , Masculino , Bulbo/citologia , Neurônios Motores/fisiologia , Rede Nervosa/citologia , Nervo Frênico/fisiologia , Núcleos da Rafe/fisiologia , Núcleos da Rafe/ultraestrutura , Ratos , Ratos Sprague-Dawley , Centro Respiratório/metabolismo , Núcleos Vestibulares/fisiologia , Núcleos Vestibulares/ultraestruturaRESUMO
The data concerning the effects of age on the brainstem are inconsistent, and few works are devoted to the human vestibular nuclear complex. The medial vestibular nucleus (MVN) is the largest nucleus of the vestibular nuclear complex, and it seems to be related mainly to vestibular compensation and vestibulo-ocular reflexes. Eight human brainstems have been used in this work. The specimens were embedded in paraffin, sectioned, and stained by the formaldehyde-thionin technique. Neuron profiles were drawn with a camera lucida at x330. Abercrombie's method was used to estimate the total number of neurons. We used the test of Kolmogorov-Smirnov with the correction of Lilliefors to evaluate the fit of our data to a normal distribution, and a regression analysis was performed to determine if the variation of our data with age was statistically significant. The present study clearly shows that neuronal loss occurs with aging. The total number of neurons decreases with age, from 122,241 +/- 651 cells in a 35-year-old individual to 75,915 +/- 453 cells in an 89-year-old individual. Neuron loss was significant in the caudal and intermediate thirds of the nucleus, whereas the changes in the rostral third were not significant. The nuclear diameter of surviving neurons decreased significantly with age. There is a neuron loss in the MVN that seems to be age-related. It could help explain why elderly people find it hard to compensate for unilateral vestibular deficits. The preservation of neurons in the rostral third could be related to the fact that this area primarily innervates the oculolmotor nuclei; these latter neurons do not decrease in number in other species studied.
Assuntos
Envelhecimento/fisiologia , Neurônios Aferentes/citologia , Núcleos Vestibulares/citologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Cadáver , Contagem de Células , Humanos , Masculino , Pessoa de Meia-Idade , Neurônios Aferentes/ultraestrutura , Análise de Regressão , Núcleos Vestibulares/ultraestruturaAssuntos
Encéfalo/fisiologia , Neurônios/fisiologia , Nervo Vestibular/fisiologia , Animais , Potenciais da Membrana/fisiologia , Microeletrodos , Neurônios/citologia , Neurônios/ultraestrutura , Perfusão , Rana ridibunda , Sinapses/fisiologia , Núcleos Vestibulares/citologia , Núcleos Vestibulares/fisiologia , Núcleos Vestibulares/ultraestruturaRESUMO
The development of the human lateral vestibular nucleus was studied on serial sections of the brain of 8 fetuses and neonates at 12-40 weeks of gestation, an infant at 2 months of age and an adult of 63 years using a microscope with a drawing tube and an image-analysing computer system. A morphometric analysis revealed that the lateral vestibular nucleus, whose neurons were distinguished from glia after 16 weeks of gestation, divided cytoarchitectonically into the medial and the lateral subnuclei at 21 weeks of gestation onwards, and showed the moderate development in terms of the columnar length and volume, neuronal size and neuropil.
Assuntos
Núcleos Vestibulares/embriologia , Núcleos Vestibulares/crescimento & desenvolvimento , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Pessoa de Meia-Idade , Neurônios/ultraestrutura , Gravidez , Núcleos Vestibulares/ultraestruturaRESUMO
Previous studies suggested that intramacular, unmyelinated segments of vestibular afferent nerve fibers and their large afferent endings (calyces) on type I hair cells branch. Many of the branches (processes) contain vesicles and are presynaptic to type II hair cells, other processes, intramacular nerve fibers, and calyces. This study used serial section transmission electron microscopy and three-dimensional reconstruction methods to document the origins and distributions of presynaptic processes of afferents in the medial part of the adult rat utricular macula. The ultrastructural research focused on presynaptic processes whose origin and termination could be observed in a single micrograph. Results showed that calyces had 1) vesiculated, spine-like processes that invaginated type I cells and 2) other, elongate processes that ended on type II cells pre- as well as postsynaptically. Intramacular, unmyelinated segments of afferent nerve fibers gave origin to branches that were presynaptic to type II cells, calyces, calyceal processes, and other nerve fibers in the macula. Synapses with type II cells occurred opposite subsynaptic cisternae (C synapses); all other synapses were asymmetric. Vesicles were pleomorphic but were differentially distributed according to process origin. Small, clear-centered vesicles, approximately 40-60 nm in diameter, predominated in processes originating from afferent nerve fibers and basal parts of calyces. Larger vesicles approximately 70-120 nm in diameter having approximately 40-80 nm electron-opaque cores were dominant in processes originating from the necks of calyces. Results are interpreted to indicate the existence of a complex system of intrinsic feedforward (postsynaptic)-feedback (presynaptic) connections in a network of direct and local microcircuits. The morphological findings support the concept that maculae dynamically preprocess linear acceleratory information before its transmission to the central nervous system.
Assuntos
Máculas Acústicas/ultraestrutura , Orelha Interna/ultraestrutura , Terminações Pré-Sinápticas/ultraestrutura , Núcleos Vestibulares/ultraestrutura , Animais , Masculino , Microscopia Eletrônica , Ratos , Ratos Sprague-DawleyRESUMO
The cellular and subcellular localization of Rxt1 protein, an orphan Na+/Cl(-)-dependent transporter, was investigated in the central nervous system of rats and mice, with rabbit polyclonal antibodies specifically directed against its C-terminal region. At the light microscope level, the distribution of Rxt1, visualized by the immunoperoxidase method, was found to be similar in rats and mice. Labelled elements were present in numerous gray matter regions of the central nervous system, from the olfactory bulb to the spinal cord. In all labelled regions, immunoreactivity was confined to the neuropil where both a diffuse labelling of low intensity and an intense punctate staining were noted. To further identify the nature of the cellular elements bearing the punctate staining, possible changes in this labelling pattern were investigated: (i) in deep cerebellar nuclei and lateral vestibular nucleus of the Lurcher mutant mouse, in which all cerebellar Purkinje cells are missing and (ii) in the rat cervical spinal cord, 10 days after multiple resections of dorsal roots. The vast majority of the punctate structures, delineating the neuronal perikaryal and stem dendritic contours, had disappeared in the mutant mouse, providing evidence that they belong to Purkinje cell axon terminals. In rhizotomized rats, the intense labelling in laminae I and III had disappeared, demonstrating that it occurred in subclasses of axonal projections of primary afferent fibres. These results strongly suggest that Rxt1 is present in presynaptic axon terminals. The electron microscopic study was carried out in the hippocampus, cerebellum and lateral vestibular nucleus of control mice, where Rxt1-labelled punctate structures were found to be abundant. Immunostaining was confined to axon terminals, particularly in hippocampal and cerebellar mossy fibres and in Purkinje cell axonal terminations of the cerebellar deep nuclei and lateral vestibular nucleus. In the cerebellar cortex, axon terminals belonging to inhibitory local circuit neurons (basket and Golgi cells), were free of labelling. The observations reported in this study have shown that: (1) The Rxt1 transporter is neuron-specific, and is expressed by only some classes or even subclasses of neuronal systems. (2) This transporter can be encountered in excitatory axons using glutamate as neurotransmitter (hippocampal and cerebellar mossy fibres: primary afferent fibres), as well as in inhibitory axons known by their GABAergic nature (Purkinje cell axon terminals) where it might be involved in the re-uptake process of one or several molecules released from corresponding terminals.
Assuntos
Proteínas de Transporte/metabolismo , Sistema Nervoso Central/metabolismo , Proteínas de Membrana Transportadoras , Proteínas do Tecido Nervoso/metabolismo , Animais , Autorradiografia , Sistema Nervoso Central/anatomia & histologia , Sistema Nervoso Central/ultraestrutura , Núcleos Cerebelares/anatomia & histologia , Núcleos Cerebelares/metabolismo , Núcleos Cerebelares/ultraestrutura , Córtex Cerebral/anatomia & histologia , Córtex Cerebral/metabolismo , Córtex Cerebral/ultraestrutura , Imuno-Histoquímica , Masculino , Camundongos , Camundongos Mutantes Neurológicos , Microscopia Eletrônica , Ratos , Ratos Sprague-Dawley , Frações Subcelulares/metabolismo , Frações Subcelulares/ultraestrutura , Núcleos Vestibulares/anatomia & histologia , Núcleos Vestibulares/metabolismo , Núcleos Vestibulares/ultraestruturaRESUMO
Intracellular recordings from 200 identified extraocular motoneurons in the bilateral III, IV and VI cranial nuclei were studied to determine the connectivities between the utricular nerve and the extraocular motoneurons in cats. Stimulating electrodes were placed within the left utricular nerve, while other branches of the vestibular nerve were removed. Monosynaptic and disynaptic connections between the utricular nerve and the ipsilateral abducens motoneurons and interneurons were recorded as described previously. Stimulation of the utricular nerve evoked longer latency depolarizing and hyperpolarizing potentials in contra- and ipsilateral medial rectus motoneurons, respectively. Depolarizing and hyperpolarizing potentials with longer latencies were also recorded in the ipsilateral inferior oblique and contralateral trochlear motoneurons. The short and longer latency circuits between the utricular nerve and extraocular motoneurons may play a role in stabilizing the retinal image during head tilt and horizontal linear acceleration.