Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Vestibular Neuronitis”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,279 records · Page 71Linked to original sources
PubMed2002

Plasticity of gamma-aminobutyrate receptors in the medial vestibular nucleus of rat after inferior cerebellar peduncle transection.

Extracellular single unit recordings were made from regularly discharging medial vestibular nucleus neurons in brain slices from control rats and from rats surviving 7 days after bilateral transection of the inferior cerebellar peduncle. Decreases in firing rate during perfusion with the gamma-aminobutyric acid (GABA) agonists, muscimol (GABA(A)) and baclofen (GABA(B)), were greater in lesioned rats than in control rats. For the grouped data, the half-maximally-effective concentrations of muscimol and baclofen were 3.2 microM, as compared with 19.6 microM for control, and 0.8 microM, as compared with 2.7 microM for control, respectively. The antagonists bicuculline (GABA(A)) and 2-OH-saclofen (GABA(B)) only minimally affected the spontaneous firing rates of neurons in lesioned rats, significantly less than in control rats. The data suggest that the decreases of endogenous GABA levels in the medial vestibular nucleus after inferior cerebellar peduncle transection are accompanied by up-regulation of GABA(A) and, to a lesser extent, GABA(B) receptors.

Animals↗
PubMed1981

[Vestibular pharmacology (author's transl)].

The paper deals with recent advances in anatomical, physiological, biochemical and pharmacological studies on the vestibular system. Fiber connections and characteristics of neurons in the vestibular nuclei were discussed in relation to regulation from other structures such as the cerebellum, oculomotor nuclei, reticular formation and spinal cord. In addition, a review was made of the actions on the vestibular system of antivertigo drugs including anticholinergic and antihistamine drugs, tranquilizers and barbiturates. All the obtained data show that the vestibular nuclei are devoid of noradrenergic, dopaminergic and serotonergic innervation, in contrast to other brainstem nuclei. Acetylcholine is apparently a neurotransmitter in the afferent transmission from the vestibular nerve to the vestibular nuclei. Antivertigo drugs produce modification in the neuron activity in the medial and lateral vestibular nuclei.

Acetylcholine↗
PubMed1991

Vestibular evoked potentials to angular acceleration in the guinea pig. A preliminary report.

Rotational evoked potentials were studied in the guinea pig under urethane anesthesia. The stimulus events were triangular velocity changes produced by abrupt reversals of acceleration, and horizontal semicircular canals were stimulated. A positive-negative-positive wave was recorded in the vestibular nuclei and the potential was totally abolished after bilateral labyrinthectomy. Single unit recordings revealed that the peak latency of the negative wave is almost coincident with the peak latency of the excitation of type I vestibular nucleus neurons. It is concluded that the recorded potential to the rotational stimuli in this experiment is of vestibular origin.

Acceleration↗
PubMed1993

Rostrocaudal changes in neuronal cell size in human lateral vestibular nucleus.

A cytoarchitectonic and morphometric study of the human lateral vestibular nucleus (LVN) is presented. In sagittal sections, the LVN appears as a triangular cell group rostrally located near the motor trigeminal nucleus and caudally near the vestibular root. The estimated volume is 13.49 mm3 with a neuronal population of 25,046 cells and 1855 neurons/mm3 in density. The average neuronal cross-sectional area changes from a minimum caudally (380.02 +/- 7.23 microns 2) to a maximum rostrally (825.16 +/- 25.10 microns 2). Four types of neurons can be observed: small (< 200 microns 2), medium (200-500 microns 2), large (500-100 microns 2) and giant or Deiter's cells (> 1000 microns 2). The small and medium cells constitute 62%, large cells 26% and the giant cells only 12% of the neuronal population.

Adult↗
PubMed1990

Ultrastructural study of synapses at the time of neuronal migration and early differentiation in the tangential vestibular nucleus of the chick embryo in vivo.

The chick tangential nucleus is a primary vestibular nucleus whose two main neuron types migrate and begin to differentiate between 5 and 8 days in the embryo (gestation takes 20-21 days). Based on rapid Golgi impregnations of developing tangential neurons and growing fibers, we have identified ultrastructural counterparts and characterized interactions in the nucleus from 5 to 8 days. Developing tangential neurons received the earliest synapses at 5 days on their primitive processes and subsequently on their cell bodies by longitudinal fibers of unknown origins. In contrast, the primary vestibular afferents did not form identified synapses on the developing tangential neurons until 7 1/2 days. In conclusion, the earliest synapses in the tangential nucleus are formed by longitudinal fibers, which are probably not primary vestibular afferents. Since a specific class of fibers forms particular synapses on the tangential neuron precursors at predictable times prior to and during neuronal migration and also at the onset of differentiation, the role of these synapses in developmental events should be explored.

Animals↗
PubMed2005

Characterization of mitochondrial respiratory chain energetics in the vestibular nucleus complex.

CONCLUSIONS: Despite having very high neuronal firing rates, the VNC does not have unusually high mitochondrial activity in vitro. This study is the first in which functionally active mitochondria from the hindbrain have been isolated and characterized. OBJECTIVE: Neurons in the vestibular nucleus complex (VNC) have exceptionally high spontaneous firing rates. Neuronal mitochondria generate adenosine triphosphate critical for maintaining the membrane potentials required for axon firing. We therefore hypothesized a high rate of mitochondrial activity in the VNC. MATERIAL AND METHODS: To test this hypothesis, we compared mitochondrial activity in the VNC with mitochondrial activity from another area of the hindbrain, the cerebellum. Mitochondrial respiratory activity was assessed by measuring oxidative phosphorylation and mitochondrial respiratory enzyme complex activity. RESULTS: Assay results were not significantly different in the VNC compared to those obtained with the cerebellum or with rat brain mitochondria in previous studies.

Adenosine Triphosphate↗
PubMed1993

Middle ear procaine injection before surgical labyrinthectomy reduces nystagmus.

A middle ear injection of 2% procaine (0.1 ml) was given to guinea-pigs 15-30 min before a surgical unilateral labyrinthectomy (UL) and the effects on spontaneous ocular nystagmus (SN) were observed. The pre-UL injection of procaine significantly reduced SN frequency compared to vehicle-injected controls or to animals receiving a post-UL injection of procaine. This result supports the hypothesis that the decrease in resting activity observed in vestibular nucleus neurones following UL may be due, at least in part, to Ca2+ influx due to injury-related glutamate release from vestibular nerve terminals.

Animals↗
PubMed2006

Precerebellar hindbrain neurons encoding eye velocity during vestibular and optokinetic behavior in the goldfish.

Elucidating the causal role of head and eye movement signaling during cerebellar-dependent oculomotor behavior and plasticity is contingent on knowledge of precerebellar structure and function. To address this question, single-unit extracellular recordings were made from hindbrain Area II neurons that provide a major mossy fiber projection to the goldfish vestibulolateral cerebellum. During spontaneous behavior, Area II neurons exhibited minimal eye position and saccadic sensitivity. Sinusoidal visual and vestibular stimulation over a broad frequency range (0.1-4.0 Hz) demonstrated that firing rate mirrored the amplitude and phase of eye or head velocity, respectively. Table frequencies >1.0 Hz resulted in decreased firing rate relative to eye velocity gain, while phase was unchanged. During visual steps, neuronal discharge paralleled eye velocity latency (approximately 90 ms) and matched both the build-up and the time course of the decay (approximately 19 s) in eye velocity storage. Latency of neuronal discharge to table steps (40 ms) was significantly longer than for eye movement (17 ms), but firing rate rose faster than eye velocity to steady-state levels. The velocity sensitivity of Area II neurons was shown to equal (+/- 10%) the sum of eye- and head-velocity firing rates as has been observed in cerebellar Purkinje cells. These results demonstrate that Area II neuronal firing closely emulates oculomotor performance. Conjoint signaling of head and eye velocity together with the termination pattern of each Area II neuron in the vestibulolateral lobe presents a unique eye-velocity brain stem-cerebellar pathway, eliminating the conceptual requirement of motor error signaling.

Animals↗
PubMed2001

A model of cerebellar computations for dynamical state estimation.

The cerebellum is a neural structure that is essential for agility in vertebrate movements. Its contribution to motor control appears to be due to a fundamental role in dynamical state estimation, which also underlies its role in various non-motor tasks. Single spikes in vestibular sensory neurons carry information about head state. We show how computations for optimal dynamical state estimation may be accomplished when signals are encoded in spikes. This provides a novel way to design dynamical state estimators, and a novel way to interpret the structure and function of the cerebellum.

Acceleration↗
PubMed2004

Neurotrophins in the ear: their roles in sensory neuron survival and fiber guidance.

We review the history of neurotrophins in the ear and the current understanding of the function of neurotrophins in ear innervation, development and maintenance. Only two neurotrophins, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), and their receptors, tyrosine kinase B (TrkB) and TrkC, appear to provide trophic support for inner ear sensory neuron afferents. Mice lacking either both receptors or both ligands lose essentially all sensory innervation of targets in the vestibular and auditory systems of the ear. Analyzes of single mutants show less complete and differential effects on innervation of the different sensory organs within the ear. BDNF and TrkB are most important for survival of vestibular sensory neurons whereas NT-3 and TrkC are most important for survival of cochlear sensory neurons. The largely complementary roles of BDNF to TrkB and NT-3 to TrkC signaling do not reflect specific requirements for innervation of different classes of hair cells. Most neurons express both receptors. Instead, the losses observed in single mutants are related to the spatio-temporal expression pattern of the two neurotrophins. In an area where only one neurotrophin is expressed at a particular time in development, the other neurotrophin is not present to compensate for this absence, resulting in death of neurons innervating that region. Decisive evidence for this suggestion is provided by transgenic mice in which the BDNF coding region has been inserted into the NT-3 gene, resulting in expression of BDNF instead of NT-3. The expression of BDNF in the spatio-temporal pattern of NT-3 results in survival of almost all neurons that are normally lost in the NT-3 mutant. Thus, BDNF and NT-3 have a high level of functional equivalence for inner ear sensory neuron survival. Further analysis of the patterns of afferent fiber losses in mutations that do not develop differentiated hair cells shows that the expression of neurotrophins is remarkably strong and can support afferent innervation. Indeed, BDNF may be one of the earliest genes expressed selectively in hair cells and it appears to be regulated somewhat independently of the genes needed for hair cell differentiation.

Animals↗
PubMed2001

Development of the gravity sensing system.

The utricle and saccule contain hair cells, which are the peripheral sensors of change in gravity that transmit signals regarding these changes to the neural components of the vestibular system. Although the fundamental neural pathways, especially the vestibular reflex pathways, have been investigated extensively, the principals underlying the functional development of this system are under study at present. The objective of this review is to identify the gravity-sensing components of the vestibular system and to present an overview of the research performed on their development. The second part of this review is focused on one important aspect of development, the emergence of electrical excitability using the chick tangential vestibular nucleus as a model. The importance of this research to understanding vestibular compensation and vestibular disturbance during spaceflight is considered. Because there is a conservation of the fundamental pathways and function in vertebrate phylogeny from birds through mammals, findings from studies on avians should contribute significantly to understanding the mechanisms operating in mammals. Also, we expect that as the events and basic mechanisms underlying normal vestibular development are revealed, these will provide practical tools to investigate the pattern of recovery from dysfunction of the vestibular system. This is related to the evidence suggesting that recovery of function in different systems and cell lines, including neurons, involves repeating certain patterns established during development.

Animals↗
PubMed1992

Projections of vertical eye movement-related neurons in the interstitial nucleus of Cajal to the vestibular nucleus in the cat.

In two alert cats, single-unit activity of neurons related to vertical eye movement was recorded in and around the interstitial nucleus of Cajal (INC), and their projections to the ipsilateral vestibular nucleus and response to stimulation of the contralateral vestibular nerve were examined. Of 62 neurons that discharged in relation to vertical eye movement, 41 increased their firing rate for downward positions and 21 for upward positions. About one third of downward-on neurons was antidromically activated by stimulation of the ipsilateral vestibular nucleus with thresholds of 36-220 microA. None of the upward-on neurons were antidromically activated. About 60% of INC neurons (22/36) responded orthodromically to stimulation of the contralateral vestibular nerve. In particular, all the downward-on neurons that projected to the ipsilateral vestibular nucleus exhibited orthodromic responses at disynaptic latencies. The results, together with our previous finding that excitatory secondary vestibular neurons carrying vertical position signals project contralaterally to the INC, suggest that downward-on INC neurons receive direct connection from these secondary vestibular neurons and send the signals back to the ipsilateral vestibular nucleus. Interstitio-vestibular interactions through these pathways may be important in the generation of vertical eye position signals.

Animals↗