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PubMed1978

[Neuronal structure of the frog vestibular ganglion].

Neuronal organization of the vestibular ganglion of the nerve VIII in the frog (Rana temporaria) has been studied by means of light and electron microscopy. It has been stated that bipolar ganglion-forming neurons are not quite identical in their structure. They differ in size, fine organization of their cytoplasm and in the manner they construct their glial sheaths. Among ganglial neurons, two types are distinguished: myelinizated and unmyelinizated neurons. A considerable part is composed by neurons coated with myelin sheath which can be constructed according to compact or loose type of myelin. Myelinizated neurons are mostly large cells, with their cytoplasm saturated with organells. Unmyelinizated neurons are coated with a simple sheath composed of one layer of lemmocytes processes. These neurons are much smaller in size, their cytoplasm is poor in organells and contains large amount of neurophilaments.

Animals↗
PubMed1997

Lack of biocytin transfer at gap junctions in the chicken vestibular nuclei.

In vivo experiments were designed to test for functional gap junctions at 'mixed' synapses that were morphologically characterized between the large-diameter, primary vestibular fibers and second-order vestibular neurons in the chicken, Gallus gallus. In previous intracellular recordings and dye injections into these neurons from brain slice preparations of chick embryos (E15/16) and also newborn hatchlings (HI-2), no evidence was obtained for functional gap junctions. Therefore, biocytin, a low molecular weight tracer that permeates gap junction channels, was extracellularly applied to either the ampullary nerves or to the vestibular ganglion of 3-6 day old hatchlings and adult chickens (9 months). This procedure resulted in the uptake of the dye and heavy staining of both the thick and thin fibers composing the vestibular nerve and in loading of vestibular efferent neurons. However, no dye transfer was observed between the large-diameter, primary vestibular fibers and second-order vestibular neurons. This observation, which was performed using a relatively non-invasive approach on intact animals, suggests that the gap junctions at these mixed synapses are probably not functional under the conditions of these experiments.

Animals↗
PubMed1997

[Squirrel monkey--an ideal primate (correction of prmate) model of space physiology].

Investigation of the vestibulo-ocular system of the squirrel monkey was reviewed in consideration of space motion sickness (SMS), or which is recently more often termed as space adaptation syndrome (SAS). Since the first launching of the space satellite, Sputnik [correction of Sputonik] in October 1957, many experiments were carried out in biological and medical fields. A various kind of creatures were used as experimental models from protozoa to human beings. Rats and monkeys are most favorite animals, particularly the non-human primate seems to be the one, because of its phylogenetic relatives akin to the human beings. Chimpanzees, rhesus monkeys, pig tailed-monkeys, red-faced monkeys and squirrel monkeys have been used mostly in American space experiments. Russian used rhesus monkeys. Among these, however, the squirrel monkey has an advantage of the small size of the body, ranging from 600- l000g in adult. This small size as a primate is very advantageous in experiments conducted in a narrow room of the space satellite or shuttle because of its space-saving. The squirrel monkey has another advantage to rear easily as is demonstrated to keep it as a pet. Accordingly, this petit animal provides us a good animal model in biological and medical experiments in space craft. The size of the brain of the squirrel monkey is extraordinary large relative to the body size, which is even superior to that of the human beings. This is partly owed to enlargement of the occipito-temporal cortices, which are forced to well develop for processing a huge amount of audio-visual information indispensable to the arboreal habitant to survive in tropical forest. The vestibular system of the squirrel monkey seems to be the most superior as well, when judged from it relative size of the vestibular nuclear complex. Balancing on swinging twigs or jumping from tree to tree developed the capability of this equilibrium system. Fernandez, Goldberg and his collaborators used the squirrel monkey to elucidate functions of the peripheral vestibular system. A transfer function was proposed to explain the behaviors of regular and irregular unit activity of vestibular nerve fibers. The physiologic characteristics of the second order vestibular neuron was investigated in combination of electrophysiological and micro-morphological way, with using WGA-HRP methods, in relation to somato-motor and eye movements. Interconnections between vestibular neurons and cerebellum, interstitial nucleus of Cajal, oculomotor nuclear complex, superior colliculus and cervical spinal cord were elucidated. In physiological field of the vestibular system, the vestibulo-ocular reflex is well studied and results obtained from the squirrel monkey experiments were reviewed. The squirrel monkey, particularly the Bolivian, is a unique animal in that it is vulnerable to motion sickness induced by visual-motion stimulation with phase mismatch of the two stimuli. Experimental results of labyrinthectomy or bilateral ablation of the maculae staticae led to the conclusion that both semicircular and otolith organs are involved in the genesis of space motion sickness. On the other hand, destruction of the area postrema, acknowledged as the vomiting center to chemical stimulants, produced controversial results. However, it must be pointed out that the a human subject underwent to resection of the area postrema, became insensitive to administration of apomorphine, a well known chemical stimulant of vomiting. Finally the experiments in space revealed the presence of at least two origins of caloric nystagmus, that is, attributable to convection and non-convection current of the endolymphatic fluid.

Acoustic Maculae↗
PubMed1993

Retro-labyrinthine disorder in cases with peripheral facial palsy.

In some previously reported cases, facial palsy, even in Bell's palsy, involved vestibular dysfunction. Vestibular dysfunction in facial palsy is considered to be due to a retro-labyrinthine disorder such as vestibular neuronitis or acoustic neuromas. For the past 9 years we have been using the galvanic body sway test (GBST) routinely for differential diagnosis of the vestibular system. This paper reports GBST detected, retro-labyrinthine disorders in facial palsy. From 1981 to 1989, equilibrium examinations were performed in 33 cases with Bell's palsy and in 12 cases with Hunt's syndrome within 2 weeks after the onset. GBST was tested in 10 out of the 17 cases showing canal paresis (CP) in the caloric test. Abnormal GBST responses were detected in 9 cases (90%), 4 (80%) with Bell's palsy and 5 (100%) with Hunt's syndrome. The incidence of abnormal GBST was very high not only in Hunt's syndrome but also in Bell's palsy. The results indicate that vestibular dysfunction combined with facial palsy is mainly due to a retro-labyrinthine disorder and suggest that what is called vestibular neuronitis might be caused by a pathogenesis similar to that of facial palsy.

Caloric Tests↗
PubMed1995

'Vestibular compensation': neural plasticity and its relations to functional recovery after labyrinthine lesions in frogs and other vertebrates.

Removal of the labyrinthine organs on one side is followed by a number of severe postural and dynamic reflex deficits. Some of these deficits, in particular the posture of head and body, are normalized again over a period that varies strongly between species. Other, more persistent motor deficits are substituted, e.g. by the saccadic system. This partial normalization of the function is accompanied by changes in response properties of the central vestibular neurons on the operated side. Available evidence suggests the occurrence of reactive synaptogenesis in cat and frog. In the latter species the synaptic efficacy of commissural vestibular connections increases and the metabolic activity of central vestibular neurons on the operated side recovers post-operatively. The onset of both changes, however, is delayed by about 30 days, which is too late to be causally related with the initial, rapid period of postural recovery in frog and cat. In frogs additional, early (7-15 days p.o.) and late (45-60 p.o.) synaptic changes were detected in the branchial spinal cord. These multiple changes survive the isolation of the spinal cord and must be propriospinal in origin. Selective lesions of individual vestibular nerve branches indicate that inactivation of utricular inputs is a sufficient and necessary condition to provoke postural deficits and early spinal changes similar to those after hemilabyrinthectomy. Therefore, a close correlation between spinal plasticity and postural recovery is indicated. In essence, the elimination of vestibular afferent inputs results in a series of behavioral distortions that are partially normalized by a multitude of synaptic mechanisms at distributed anatomical sites over different periods of time.

Animals↗
PubMedDate not supplied

Microcomputer-based spike train analysis.

A system has been developed to analyse statistically the information contained within neuronal spike trains in the central nervous system. The system consists of a microprocessor development system, together with the peripheral components and transducers. Suitable software packages have been developed to analyse statistical parameters including the mean, variance, entropy, conditional entropy, serial correlation coefficients, Markov dependency and Markov order. By linking up the required routines, the system is capable of responding in real-time and plotting the desired results from the spike train obtained. Such system has been used to study the neuronal spike trains recorded from central vestibular neurons which could be affected by positional changes, anaesthetics and various drugs for the relief of motion sickness.

Animals↗
PubMed2000

Postnatal developmental changes in AMPA and NMDA receptors in the rat vestibular nuclei.

Changes in the expression of the AMPA receptor subunits GluR1-4 and of the NMDA receptor subunits NR1, NR2A-D were investigated in the developing rat medial and lateral vestibular nuclei. Analyses were performed using nonradioactive in situ hybridization and immunoblotting with subunit-specific antibodies. During the postnatal development, glutamatergic receptor subunits were differentially expressed in the vestibular nuclei. The level of expression of GluR1, GluR4 and NR1 subunits was higher in the developing brain as compared to the adult. We observed a gradual increase in GluR2/3, NR2A, NR2B and NR2C levels of expression in the medial and lateral vestibular nuclei during the first 3 weeks of postnatal development. In situ hybridization results were consistent with immunoblot analyses. The differential expression of AMPA and NMDA receptor subunits in immature vestibular neurons is consistent with changes in glutamate receptor properties. This may be related to the postsynaptic regulation of receptor subunits associated with the synaptic plasticity of the vestibular neuron connections during specific sequences of postnatal development.

Animals↗
PubMed2005

Treatment of vertigo.

Vertigo is the illusion of motion, usually rotational motion. As patients age, vertigo becomes an increasingly common presenting complaint. The most common causes of this condition are benign paroxysmal positional vertigo, acute vestibular neuronitis or labyrinthitis, Ménière's disease, migraine, and anxiety disorders. Less common causes include vertebrobasilar ischemia and retrocochlear tumors. The distinction between peripheral and central vertigo usually can be made clinically and guides management decisions. Most patients with vertigo do not require extensive diagnostic testing and can be treated in the primary care setting. Benign paroxysmal positional vertigo usually improves with a canalith repositioning procedure. Acute vestibular neuronitis or labyrinthitis improves with initial stabilizing measures and a vestibular suppressant medication, followed by vestibular rehabilitation exercises. Meniere's disease often responds to the combination of a low-salt diet and diuretics. Vertiginous migraine headaches generally improve with dietary changes, a tricyclic antidepressant, and a beta blocker or calcium channel blocker. Vertigo associated with anxiety usually responds to a selective serotonin reuptake inhibitor.

Diagnosis, Differential↗
PubMed1989

Vestibulo-ocular and vestibulo-spinal reflexes in evaluation of vestibular lesions.

In order to evaluate to what extent different diseases causing vertigo can be detected by studying vestibulo-spinal and vestibulo-ocular reflexes, 146 patients were examined. The diagnosis classes were: periodical attacks, position induced attacks, vestibular neuronitis, brain concussion, cerebrovascular disorders and acoustic neurinoma. Dynamic posturography was performed on all the patients, standard bithermal caloric test on 129 and voluntary saccades on 127 patients. The proportion of pathological test results in posturography exceeded that in the caloric test in all but one diagnosis class. In vestibular neuronitis the amount of abnormal test results was low in posturography, probably due to vestibular compensation. Posturography tested with eyes open and with 80 Hz vibration revealed disturbances in equilibrium the most sensitively.

Caloric Tests↗
PubMed2002

Gradual and reversible central vestibular reorganization in frog after selective labyrinthine nerve branch lesions.

Postlesional reorganization of vestibular afferent and commissural inputs onto second-order vestibular neurons was studied in the isolated brain after unilateral section of the N.VIII, of the ramus anterior (RA) of N.VIII, of the utricular (UT) or of the anterior vertical and horizontal canal nerves in combination. RA nerve section eliminated the inputs from utricular, anterior vertical and horizontal canal organs. In the first set of experiments we recorded field potentials on the operated side of the vestibular nuclei 2 months after RA nerve section. These responses were evoked by electrical stimulation of the RA nerve or of the posterior vertical canal nerve on the operated or on the intact side. The amplitudes of afferent field potentials evoked by stimulation of the spared posterior vertical canal nerve were increased. The amplitudes of afferent field potentials evoked by stimulation of the axotomized RA nerve remained unaltered. After N.VIII section the commissural, but not the afferent, field potentials increased significantly on the operated side following stimulation of N.VIII on the intact and on the operated side, respectively. After UT nerve section no change in commissural but an increase in the amplitude of afferent field potentials from each of the three intact canal nerves was observed on the operated side. In the context of earlier results these findings imply that second-order vestibular neurons, disfacilitated due to afferent nerve section, became receptive to additional, excitatory synaptic inputs, preferentially from intact vestibular nerve afferent fibers. The reduced excitation via afferent nerve inputs was thereby replaced by other afferent nerve inputs from spatially inadequate vestibular end-organs. The synaptic terminals of inactivated afferent nerve fibers were maintained and not repressed. The process of central reorganization after vestibular nerve lesion was activity related, the expansion of signals restricted to inputs from intact fibers, its extent graded and its onset delayed with respect to the onset of corresponding spinal changes and to the onset of postural recovery after the same type of nerve lesion. After the section of RA nerve or of an individual nerve branch the labyrinthine end-organs remained intact and were not removed as after unilateral labyrinthectomy (UL). Peripheral reinnervation of the end-organs was thus excluded after UL, but expected after one of the former types of lesion. Functional reinnervation of the utricular macula was mirrored behaviorally by the reappearance of severe postural deficits following a second RA nerve section. These lesion-induced postural deficits began to reappear if the repeated RA nerve section was delayed with respect to the first by about 3 months. We therefore studied postlesional reorganization in the brainstem 3 months after the first RA nerve section. Reinnervation of the utricular macula was accompanied by a rapid decline of the increased amplitudes of afferent and commissural vestibular field potentials towards control values, suggesting the reversibility of the lesion-induced central reorganization.

Afferent Pathways↗
PubMed1981

[The perverted nystagmus (author's transl)].

The perverted nystagmus is a modification of the horizontal beating nystagmus (in classical caloric stimulation) by a vertical or rotatory mainly component. Experimentally, this disorder can be shown after an unilateral destroy of the superior or median vestibular nucleus. We show 32 cases of subjects with a perverted nystagmus. 75% of these subjects have a pure central disease and 20% a vestibular neuronitis. The perverted nystagmus had an upbeat component with the cold stimulation and downbeat component with the hot stimulation. It was accompanied by a spontaneous nystagmus in 66% (and 30% with vertical nystagmus). Some abnormal responses with the simultaneous bilateral vestibular caloric testing, were found in 95%. The analysis of the results of the unilateral caloric testing shown the frequent association: hyporeflectia (canal paresis) of one side and hyper-reflects of the other side. This fact would have evoked a mixed disease, peripheric and central (i.e. the vestibular neuronitis). Beside some pathogenic hypothesis, we prefer the fall of the inhibiting control of the superior semi-circular canal firing activity. Although, the perverted nystagmus is a simple and precious examination sign (it is directly shown with Frenzel glasses after caloric vestibular stimulation. It ought to do the brain stem topography diagnosis.

Adult↗