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 1,009 records · Page 56Linked to original sources
PubMedDate not supplied

[Chemical sensitivity of the neurons of the medial vestibular nucleus to enkephalins, acetylcholine, GABA and L-glutamate].

The effect of enkephalins, morphine and some neurotransmitters on spontaneous and evoked activity of neurons of the medial vestibular nucleus was investigated. The evoked activity was produced by an adequate stimulation of the vestibular apparatus. It was shown that neurons of this nucleus were highly sensitive to enkephalins, morphine, acetyl choline, GABA and L-glutamate (approximately 80% of the nerve cells were inhibited or excited in response to the micro-iontophoretic application of these substances). It was found that activation and depression effects of opioid peptides and morphine occurred due to the stimulation of mu- and delta-opiate receptors. It can be concluded that enkephalins modulate cholinergic and glutamatergic synaptic transfer in the medial vestibular nucleus. Together with opiate receptors, they participate in the perception and processing of vestibular information at the level of neurons of this nucleus.

Acetylcholine↗
PubMed1987

Convergence of neck and macular vestibular inputs on vestibulospinal neurons projecting to the lumbosacral segments of the spinal cord.

The activity of LVN neurons was recorded in decerebrate cats and analyzed during separate stimulation of macular vestibular and neck receptors elicited by sinusoidal rotation about the longitudinal axis at 0.026 Hz, 10 degrees peak amplitude. Of 119 LVN units examined, the great majority, i.e. 106, were vestibulospinal neurons antidromically identified following stimulation of the spinal cord at T12-L1, thus projecting to the lumbosacral segments of the spinal cord (IVS neurons); the remaining 13 units were nonantidromically activated. Among the 119 LVN neurons, 77 (64.7%) responded with a periodic modulation of their firing rate to roll tilt of the animal and 81 (68.1%) responded to neck rotation. Convergence of macular and neck inputs was found in 58/119 (48.7%) lateral vestibular neurons; in these units, the gain as well as the sensitivity of the first harmonic of responses corresponded on the average to 0.58 +/- 0.45, S.D. imp./sec/deg and 4.39 +/- 3.58, S.D.%/deg for the neck responses and 0.52 +/- 0.49, S.D. imp./sec/deg and 3.85 +/- 3.35, S.D.%/deg for the macular responses, respectively. In addition to these convergent units, 19/119 (16.0%) and 23/119 (19.3%) lateral vestibular units responded to selective stimulation either of macular receptors or of neck receptors only. These units, which showed on the average an higher firing rate and a lower conduction velocity of the corresponding vestibulospinal axons than the convergent units, displayed a significantly lower response gain and sensitivity to animal tilt and neck rotation with respect to those obtained from convergent units. Most of the convergent lateral vestibular units were maximally excited by the direction of stimulus orientation, the first harmonic of responses showing an average phase lead of +51.4 degrees with respect to neck position and +21.9 degrees with respect to animal position. Two populations of convergent neurons were observed. The first group of units (53/58, i.e. 91.4%) showed reciprocal ("out-of-phase") responses to the two inputs in that they were mainly excited during side-down animal tilt and side-up neck rotation. The remaining group of units (5/58, i.e. 8.6%) showed parallel ("in phase") responses to the two inputs and they were mainly excited by side-up neck rotation and animal tilt. Interestingly, the former group of units displayed an average gain and sensitivity to the labyrinth and neck inputs which were more than twice higher than the values obtained from the latter group of units.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed2001

Directional sensitivity of anterior, posterior, and horizontal canal vestibulo-ocular neurons in the cat.

Neurons subserving the vestibulo-ocular reflex transform the directionality and timing of input from semicircular canals into commands that are appropriate to rotate the eyes in a compensatory fashion. In order to assess the degree to which this transformation is evident in vestibular nucleus neurons of alert cats, we recorded the extracellular discharge properties of 138 second-order vestibular neurons in the superior and medial vestibular nucleus, including 64 neurons identified as second-order vestibulo-ocular neurons by antidromic responses to oculomotor nucleus stimulation and short-latency orthodromic responses to labyrinth stimulation (1.3 ms or less). Neuronal response gains and phases were recorded during 0.5-Hz sinusoidal oscillations about many different horizontal axes and during vertical axis rotations to define neuronal response directionality more precisely than in past studies. Neurons with spatial responses similar to anterior semicircular canal afferents were found to have more diverse maximal activation direction vectors than neurons with responses resembling those of posterior or horizontal canal afferents. The mean angle from neuron response vector to the axis of the nearest canal or canal pair was 19 degrees for anterior canal second-order neurons (n=28) and 20 degrees for anterior canal second-order vestibulo-ocular neurons (n=18), compared with 11 degrees for posterior canal second-order neurons (n=43) and 11 degrees for posterior canal second-order vestibulo-ocular neurons (n=25). Only two second-order vestibulo-ocular neurons (3%) showed a marked dependence of response phase on rotation direction, which is indicative of convergent inputs that differ in both dynamics and directionality. This suggests that spatiotemporal convergence is uncommon in the three-neuron vestibulo-ocular reflex arc of the cat. Neuron vectors included many that were closely aligned with canal axes and several that were better aligned with oblique or superior rectus extraocular muscle excitation axis vectors. Only single examples of second-order vestibulo-ocular neuron vectors were approximately aligned with the pitch and roll coordinate axes. We conclude that second-order vestibulo-ocular neurons do not exclusively represent either the semicircular canal sensory coordinate frame or the extraocular muscle excitation motor coordinate frame, and instead are mostly distributed on a continuum between the input and output coordinate frames, with anterior canal neurons having the widest distribution of directionality.

Action Potentials↗
PubMed2005

Pursuit--vestibular interactions in brain stem neurons during rotation and translation.

Under natural conditions, the vestibular and pursuit systems work synergistically to stabilize the visual scene during movement. How translational vestibular signals [translational vestibuloocular reflex (TVOR)] are processed in the premotor pathways for slow eye movements continues to remain a challenging question. To further our understanding of how premotor neurons contribute to this processing, we recorded neural activities from the prepositus and rostral medial vestibular nuclei in macaque monkeys. Vestibular neurons were tested during 0.5-Hz rotation and lateral translation (both with gaze stable and during VOR cancellation tasks), as well as during smooth pursuit eye movements. Data were collected at two different viewing distances, 80 and 20 cm. Based on their responses to rotation and pursuit, eye-movement-sensitive neurons were classified into position-vestibular-pause (PVP) neurons, eye-head (EH) neurons, and burst-tonic (BT) cells. We found that approximately half of the type II PVP and EH neurons with ipsilateral eye movement preference were modulated during TVOR cancellation. In contrast, few of the EH and none of the type I PVP cells with contralateral eye movement preference modulated during translation in the absence of eye movements; nor did any of the BT neurons change their firing rates during TVOR cancellation. Of the type II PVP and EH neurons that modulated during TVOR cancellation, cell firing rates increased for either ipsilateral or contralateral displacement, a property that could not be predicted on the basis of their rotational or pursuit responses. In contrast, under stable gaze conditions, all neuron types, including EH cells, were modulated during translation according to their ipsilateral/contralateral preference for pursuit eye movements. Differences in translational response sensitivities for far versus near targets were seen only in type II PVP and EH cells. There was no effect of viewing distance on response phase for any cell type. When expressed relative to motor output, neural sensitivities during translation (although not during rotation) and pursuit were equivalent, particularly for the 20-cm viewing distance. These results suggest that neural activities during the TVOR were more motorlike compared with cell responses during the rotational vestibuloocular reflex (RVOR). We also found that neural responses under stable gaze conditions could not always be predicted by a linear vectorial addition of the cell activities during pursuit and VOR cancellation. The departure from linearity was more pronounced for the TVOR under near-viewing conditions. These results extend previous observations for the neural processing of otolith signals within the premotor circuitry that generates the RVOR and smooth pursuit eye movements.

Action Potentials↗
PubMed1982

Distribution of beta-D-glucuronidase in the central nervous system of albino rats.

The distribution of beta-D-glucuronidase (GLR) in the central nervous system of albino rats was surveyed with a simultaneous-coupling histochemical technique. Specific neuronal populations displayed intense GLR activity. These groups include olfactory bulb mitral cells, neurones in the deep layer of the olfactory tubercle, cells in both the horizontal and vertical limbs of the nucleus of the diagonal band, paraventricular, supraoptic and suprachiasmatic nuclear neurons, cochlear and vestibular nuclear neurons, and facial, trigeminal and spinal motoneurons. Two types of intracellular GLR staining were observed. Granular staining was prominent in mitral cells; cytoplasmic staining and a perinuclear 'ring' were prominently stained in motoneurons. These patterns may correspond to lysosomal and endoplasmic reticular distribution of GLR in different cell types.

Animals↗
PubMed2003

Selective expression of beta tubulin isotypes in gerbil vestibular sensory epithelia and neurons.

The seven mammalian isotypes of beta tubulin are strikingly similar in amino acid sequence. The differences in isotypic sequence, although small, are nonetheless conserved in evolution, which suggests that they may confer distinct functional roles. If so, such roles should be reflected in the selective expression of isotypes by cell type, or even in the sorting of isotypes to within-cell pools. Hair cells of the vestibular sensory epithelia each possess a kinocilium, a microtubule-based organelle that could represent a distinct microtubule compartment, separate from the extensive microtubule network in the soma. The afferent neurons that innervate the vestibular sensory epithelia may also be functionally divided into dendritic, somatic, and axonal compartments, each with its own complement of microtubules. We have examined the distribution of beta tubulin isotypes in gerbil vestibular epithelia using isotype-specific antibodies to four isotypes and indirect immunofluorescence. We found that hair cells selectively express betaI and betaIV tubulin, while supporting cells express betaI, betaII, and betaIV tubulin. However, no sorting of isotypes between somatic and kinocilia compartments was found in hair cells. Vestibular ganglion cells display three isotypes in the soma, axon, and terminal dendrite compartments (betaI, betaII, and betaIII tubulin), but only betaIII tubulin was found in calyceal nerve endings. The implication of these findings is that beta tubulin isotypes are not sorted to within-cell compartments in hair cells but are sorted in some vestibular neurons.

Animals↗
PubMed1994

Occurrence of galanin-like immunoreactivity in vestibular and cochlear efferent neurons after labyrinthectomy in the rat.

The origins of the vestibular and cochlear efferent systems lie in the lower brainstem and innervate the labyrinth. In the present study we investigated the changes in galanin-like immunoreactivity (GAL-IR) in the vestibular and cochlear efferent neurons in control and labyrinthectomized rats. In control animals, no GAL-IR was noticed in these neurons. However, in response to unilateral labyrinthectomy, similar GAL-IR was bilaterally expressed in the two systems. GAL-immunostained cells appeared on postoperative day 3 and reached a peak of intensity and number at postoperative week 2. Retrograde tracing by fluorogold combined with GAL immunohistochemistry demonstrated that, except for the cells of the contralateral lateral superior olivary nucleus (LSO), GAL-IR neurons project into the lesioned labyrinth.

Animals↗
PubMed1991

Medial vestibular nucleus in the guinea-pig. II. Ionic basis of the intrinsic membrane properties in brainstem slices.

In the preceding paper, medial vestibular nuclei neurones (MVNn) were shown to belong to two main classes, A MVNn and B MVNn, depending on their membrane properties in brainstem slices. In the following study we attempted to confirm this segregation by studying some of the ionic conductances that these cells are endowed with. Type A MVNn demonstrated small high threshold calcium spikes that could be potentiated by barium, a 4-AP resistant A-like conductance and a calcium-dependent afterhyperpolarization. Type B MVNn, in contrast, had large high threshold calcium spikes and prolonged calcium-dependent plateau potentials. In addition, they had a calcium-dependent afterhyperpolarization as well as a subthreshold persistent sodium conductance. A subpopulation of B MVNn had also low threshold calcium spikes that gave them bursting properties. These data confirm the segregation of MVN neurones into two main classes and will be discussed with respect to the firing characteristics of vestibular neurones in vivo.

4-Aminopyridine↗