Changes in sensitivity of bilateral medial vestibular nuclear neurons responding to input stimuli during vestibular compensation and the underlying ionic mechanism / 生理学报

Vestibular compensation is an important model for developing the prevention and intervention strategies of vestibular disorders, and investigating the plasticity of the adult central nervous system induced by peripheral injury. Medial vestibular nucleus (MVN) in brainstem is critical center for vestibular compensation. Its neuronal excitability and sensitivity have been implicated in normal function of vestibular system. Previous studies mainly focused on the changes in neuronal excitability of the MVN in lesional side of the rat model of vestibular compensation following the unilateral labyrinthectomy (UL). However, the plasticity of sensitivity of bilateral MVN neurons dynamically responding to input stimuli is still largely unknown. In the present study, by using qPCR, whole-cell patch clamp recording in acute brain slices and behavioral techniques, we observed that 6 h after UL, rats showed a significant deficit in spontaneous locomotion, and a decrease in excitability of type B neurons in the ipsilesional rather than contralesional MVN. By contrast, type B neurons in the contralesional rather than ipsilesional MVN exhibited an increase in response sensitivity to the ramp and step input current stimuli. One week after UL, both the neuronal excitability of the ipsilesional MVN and the neuronal sensitivity of the contralesional MVN recovered to the baseline, accompanied by a compensation of spontaneous locomotion. In addition, the data showed that the small conductance Ca2+-activated K+ (SK) channel involved in the regulation of type B MVN neuronal sensitivity, showed a selective decrease in expression in the contralesional MVN 6 h after UL, and returned to normal level 1 week later. Pharmacological blockage of SK channel in contralateral MVN to inhibit the UL-induced functional plasticity of SK channel significantly delayed the compensation of vestibular motor dysfunction. These results suggest that the changes in plasticity of the ipsilesional MVN neuronal excitability, together with changes in the contralesional MVN neuronal sensitivity, may both contribute to the development of vestibular symptoms as well as vestibular compensation, and SK channel may be an essential ionic mechanism responsible for the dynamic changes of MVN neuronal sensitivity during vestibular compensation.

Aplicações dos potenciais evocados miogênicos vestibulares: revisão sistemática de literatura / Applications of vestibular-evoked myogenic potentials: a systematic literature review

RESUMO Objetivos Revisar a literatura científica sobre as principais técnicas usadas para gerar o potencial evocado miogênico vestibular (VEMP) e suas aplicações clínicas. Estratégia de pesquisa Os artigos que descrevem os métodos de registro e as aplicações do VEMP foram localizados nas bases de dados PubMed, Web of Science, MEDLINE, Scopus, LILACS e SciELO. O levantamento realizado limitou-se aos artigos publicados nos idiomas Inglês, Português e Espanhol, entre janeiro de 2012 e maio de 2018. Critérios de seleção Artigos sobre os aspectos técnicos para a realização do VEMP ocular, cervical ou do músculo sóleo, com estimulação auditiva ou galvânica e artigos sobre as aplicações clínicas do VEMP foram incluídos; artigos repetidos nas bases de dados, artigos de revisão de literatura, relato de casos, cartas e editoriais foram excluídos. Resultados A estratégia de busca resultou na seleção de 28 artigos. Os estudos evidenciaram três métodos de registro do VEMP: cervical, ocular e no músculo sóleo. As aplicações clínicas do VEMP incluíram doença de Ménière, neurite vestibular, síndrome da deiscência do canal semicircular superior, doença de Parkinson, lesões centrais isquêmicas e mielopatias motoras. Conclusão Independentemente da técnica de registro, o VEMP mostrou-se útil como ferramenta complementar para o diagnóstico de doenças vestibulares periféricas e centrais.

ABSTRACT Purpose To review the scientific literature on the main techniques used to generate vestibular-evoked myogenic potential (VEMP) and its clinical applications. Research strategy A search for articles describing VEMP recording methods and applications was conducted in the PubMed, Web of Science, MEDLINE, Scopus, LILACS and SciELO databases. The search was limited to articles published in English, Portuguese, and Spanish between January 2012 and May 2018. Selection criteria Articles addressing the technical aspects for performing ocular, cervical or soleus VEMP with auditory or galvanic stimulation and articles on the clinical applications of VEMP were included in this review, whereas articles repeated in the databases, literature reviews, case reports, letters, and editorials were excluded. Results The search strategy resulted in the selection of 28 articles. The studies evidenced three methods of VEMP recording: responses from the cervical, ocular and soleus muscle. Clinical applications of VEMP included Meniere's disease, vestibular neuritis, superior semicircular canal dehiscence syndrome, Parkinson's disease, central ischemic lesions, and motor myelopathies. Conclusion Regardless of the recording technique, VEMP has proved to be useful as a complementary tool for the diagnosis of peripheral and central vestibular diseases.

The Emerging Concept of Intrinsic Plasticity: Activity-dependent Modulation of Intrinsic Excitability in Cerebellar Purkinje Cells and Motor Learning

What is memory? How does the brain process the sensory information and modify an organism's behavior? Many neuroscientists have focused on the activity- and experience-dependent modifications of synaptic functions in order to solve these fundamental questions in neuroscience. Recently, the plasticity of intrinsic excitability (called intrinsic plasticity) has emerged as an important element for information processing and storage in the brain. As the cerebellar Purkinje cells are the sole output neurons in the cerebellar cortex and the information is conveyed from a neuron to its relay neurons by forms of action potential firing, the modulation of the intrinsic firing activity may play a critical role in the cerebellar learning. Many voltage-gated and/or Ca²⁺-activated ion channels are involved in shaping the spiking output as well as integrating synaptic inputs to finely tune the cerebellar output. Recent studies suggested that the modulation of the intrinsic excitability and its plasticity in the cerebellar Purkinje cells might function as an integrator for information processing and memory formation. Moreover, the intrinsic plasticity might also determine the strength of connectivity to the sub-cortical areas such as deep cerebellar nuclei and vestibular nuclei to trigger the consolidation of the cerebellar-dependent memory by transferring the information.

Role of peripheral vestibular receptors in the control of blood pressure following hypotension

Hypotension is one of the potential causes of dizziness. In this review, we summarize the studies published in recent years about the electrophysiological and pharmacological mechanisms of hypotension-induced dizziness and the role of the vestibular system in the control of blood pressure in response to hypotension. It is postulated that ischemic excitation of the peripheral vestibular hair cells as a result of a reduction in blood flow to the inner ear following hypotension leads to excitation of the central vestibular nuclei, which in turn may produce dizziness after hypotension. In addition, excitation of the vestibular nuclei following hypotension elicits the vestibulosympathetic reflex, and the reflex then regulates blood pressure by a dual-control (neurogenic and humoral control) mechanism. In fact, recent studies have shown that peripheral vestibular receptors play a role in the control of blood pressure through neural reflex pathways. This review illustrates the dual-control mechanism of peripheral vestibular receptors in the regulation of blood pressure following hypotension.

Application of Tetrode Technology for Analysis of Changes in Neural Excitability of Medial Vestibular Nucleus by Acute Arterial Hypotension / 대한평형의학회지

OBJECTIVES: Excitability o medial vestibular nucleus (MVN) in the brainstem can be affected by changes in the arterial blood pressure. Several animal studies have demonstrated that acute hypotension results in the alteration of multiunit activities and expression of cFos protein in the MVN. In the field of extracellular electrophysiological recording, tetrode technology and spike sorting algorithms can easily identify single unit activity from multiunit activities in the brain. However, detailed properties of electrophysiological changes in single unit of the MVN during acute hypotension have been unknown. METHODS: Therefore, we applied tetrode techniques and electrophysiological characterization methods to know the effect of acute hypotension on single unit activities of the MVN of rats. RESULTS: Two or 3 types of unit could be classified according to the morphology of spikes and firing properties of neurons. Acute hypotension elicited 4 types of changes in spontaneous firing of single unit in the MVN. Most of these neurons showed excitatory responses for about within 1 minute after the induction of acute hypotension and then returned to the baseline activity 10 minutes after the injection of sodium nitroprusside. There was also gradual increase in spontaneous firing in some units. In contrast small proportion of units showed rapid reduction of firing rate just after acute hypotension. CONCLUSIONS: Therefore, application of tetrode technology and spike sorting algorithms is another method for the monitoring of electrical activity of vestibular nuclear during acute hypotension.

Dual control of the vestibulosympathetic reflex following hypotension in rats

Orthostatic hypotension (OH) is associated with symptoms including headache, dizziness, and syncope. The incidence of OH increases with age. Attenuation of the vestibulosympathetic reflex (VSR) is also associated with an increased incidence of OH. In order to understand the pathophysiology of OH, we investigated the physiological characteristics of the VSR in the disorder. We applied sodium nitroprusside (SNP) to conscious rats with sinoaortic denervation in order to induce hypotension. Expression of pERK in the intermediolateral cell column (IMC) of the T4~7 thoracic spinal regions, blood epinephrine levels, and blood pressure were evaluated following the administration of glutamate and/or SNP. SNP-induced hypotension led to increased pERK expression in the medial vestibular nucleus (MVN), rostral ventrolateral medullary nucleus (RVLM) and the IMC, as well as increased blood epinephrine levels. We co-administered either a glutamate receptor agonist or a glutamate receptor antagonist to the MVN or the RVLM. The administration of the glutamate receptor agonists, AMPA or NMDA, to the MVN or RVLM led to elevated blood pressure, increased pERK expression in the IMC, and increased blood epinephrine levels. Administration of the glutamate receptor antagonists, CNQX or MK801, to the MVN or RVLM attenuated the increased pERK expression and blood epinephrine levels caused by SNP-induced hypotension. These results suggest that two components of the pathway which maintains blood pressure are involved in the VSR induced by SNP. These are the neurogenic control of blood pressure via the RVLM and the humoral control of blood pressure via epinephrine release from the adrenal medulla.

The Linear Transmission of the Vestibular Neural Information by Galvanic Vestibular Stimulation / 대한평형의학회지

OBJECTIVE: Growing hypotheses indicate the galvanic vestibular stimulation (GVS) as an alternative method to manage the symptoms of parkinson's disease (PD). GVS is easy and safe for use, and non-invasive. However, it is elusive how the neural information caused by GVS is transmitted in the central nervous system and relieves PD symptoms. To answer this question, we investigated the transmission of neural information by GVS in the central vestibular system, focused on vestibular nucleus (VN). METHODS: Twenty guinea pigs were used for this study for the extracellular neuronal recordings in the VN. The neuronal responses to rotation and GVS were analyzed by curve-fitting, and the numerical responding features, amplitudes and baselines, were computed. The effects of stimuli were examined by comparing these features. RESULTS: Twenty six vestibular neurons (15 regular and 11 irregular neurons) were recorded. Comparing the difference of baselines, we found the neural information was linearly transmitted with a reduced sensitivity (0.75). The linearity in the neural transmission was stronger in the neuronal groups with regular (correlation coefficient [Cor. Coef.]=0.91) and low sensitive units (Cor. Coef.=0.93), compared with those with irregular (Cor. Coef.=0.86) and high-sensitive neurons (Cor. Coef.=0.77). CONCLUSION: The neural information by GVS was linearly transmitted no matter what the neuronal characteristics were.

Periodic Alternating Nystagmus in Patients with Cerebellar Abscess / 대한평형의학회지

Periodic alternating nystagmus (PAN) is characterized by a periodical reversal in the direction of the nystagmus. Acquired PAN is caused by lesions of the inferior cerebellar vermis, causing disinhibition of the velocity storage mechanism, which is mediated by the vestibular nuclei. An eighty-year-old woman with abscess in midline cerebellum experienced dizziness and imbalance. We observed short period PAN with 7-8 seconds.

The study of acoustically evoked short latency negative responses in normal guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To compare acoustically evoked short latency negative responses (ASNR) elicited from normal and profound hearing loss guinea pig ears and to confirm their vestibular nuclei origination.</p><p><b>METHODS</b>Forty healthy guinea pigs were employed in the experiment, which were randomly divided into the control group (8 subjects, 16 ears), the masking group (16 subjects, 32 ears) and the deafened group (16 subjects, 32 ears). Air conductive white noise was chosen for masking. Masking dilemma was avoidable by an appropriate 15 dB gap between stimulus and masking sound. Both the masking group and the deafened group were further divided into ASNR group and non-ASNR group based on the presence of ASNR. Electrolytic lesion was conducted to the vestibular nuclei, followed by ABR/ASNR recording. The lesioned brainstem slices were microscopically verified.</p><p><b>RESULTS</b>In the masking group, ASNR were present in 24 ears (75.0%, 24/32) and 12 ears (46.2%, 12/26) in deafened group, showing statistically higher presence rate for masking group (χ(2)=5.07, P=0.024). There were no significant differences for the ASNR threshold and latency between the masking ASNR group and the deafened ASNR group. For the two ASNR groups, electrolytic destruction to the vestibular nuclei subsequently eliminated the ASNR. Brainstem slice proved the accurate sites of electrolytic lesion.</p><p><b>CONCLUSION</b>Moderate white noise masking prevents hearing system potential overlap without affecting vestibular system, therefore, ASNR is successfully elicited in normal guinea pigs. Both ASNRs from normal and deafened guinea pigs are of similar natures and origination from, the vestibular nuclei.</p>

Functional Connections of the Vestibulo-spino-adrenal Axis in the Control of Blood Pressure Via the Vestibulosympathetic Reflex in Conscious Rats

Significant evidence supports the role of the vestibular system in the regulation of blood pressure during postural movements. In the present study, the role of the vestibulo-spino-adrenal (VSA) axis in the modulation of blood pressure via the vestibulosympathetic reflex was clarified by immunohistochemical and enzyme immunoassay methods in conscious rats with sinoaortic denervation. Expression of c-Fos protein in the intermediolateral cell column of the middle thoracic spinal regions and blood epinephrine levels were investigated, following microinjection of glutamate receptor agonists or antagonists into the medial vestibular nucleus (MVN) and/or sodium nitroprusside (SNP)-induced hypotension. Both microinjection of glutamate receptor agonists (NMDA and AMPA) into the MVN or rostral ventrolateral medullary nucleus (RVLM) and SNP-induced hypotension led to increased number of c-Fos positive neurons in the intermediolateral cell column of the middle thoracic spinal regions and increased blood epinephrine levels. Pretreatment with microinjection of glutamate receptor antagonists (MK-801 and CNQX) into the MVN or RVLM prevented the increased number of c-Fos positive neurons resulting from SNP-induced hypotension, and reversed the increased blood epinephrine levels. These results indicate that the VSA axis may be a key component of the pathway used by the vestibulosympathetic reflex to maintain blood pressure during postural movements.

Role of the Cerebral Cortex on Vestibular Compensation Following Unilateral Labyrinthectomy in Rats / 대한평형의학회지

OBJECTIVE: The cerebral cortex can modulate vestibular functions through direct control of neuronal activities in the vestibular nuclei. The purpose of this study was to investigate the effect of unilateral cortical lesion or cortical stimulation on static vestibular symptoms and vestibular nuclear activities at the acute stage of vestibular compensation following unilateral labyrinthectomy (UL) in rats. METHODS: The photothrombic ischemic injury using rose bengal was induced in the primary motor cortex or primary sensory cortex, and electrical stimulation was applied to the primary motor cortex, primary sensory cortex, or sencondary sensory cortex, respectively, in unilateral labyrinthectomized rats. Static vestibular symptoms including ocular movement and postural deficits, and expression of c-Fos protein in the medial vestibular nucleus (MVN) were measured. RESULTS: Lesion of the motor cortex produced a marked postural deficit with paralytic weakness in the hindlimb contralateral to UL. Number of spontaneous nystagmus in animals receiving cortical lesion was significantly increased 2, 6, and 12 hours after UL compared with animals being UL only. Lesion of the primary motor cortex or stimulation of the S2 sensory cortex decreased expression of c-Fos protein in MVN following UL compared with UL only group. Electrical stimulation of S2 sensory areas caused significant reduction of static vestibular symptoms and decreased expression of c-Fos protein in MVN 24 hours following UL. CONCLUSION: The present results suggest that cerebral cortex involves in recovery of static vestibular symptoms during vestibular compensation following UL.

Effect of Glutamate on the Vestibulo-Solitary Projection after Sodium Nitroprusside-Induced Hypotension in Conscious Rats

Orthostatic hypotension is most common in elderly people, and its prevalence increases with age. Attenuation of the vestibulo-sympathetic reflex (VSR) is commonly associated with orthostatic hypotension. In this study, we investigated the role of glutamate on the vestibulo-solitary projection of the VSR pathway to clarify the pathophysiology of orthostatic hypotension. Blood pressure and expression of both pERK and c-Fos protein were evaluated in the nucleus tractus solitarius (NTS) after microinjection of glutamate into the medial vestibular nucleus (MVN) in conscious rats with sodium nitroprusside (SNP)-induced hypotension that received baroreceptor unloading via sinoaortic denervation (SAD). SNP-induced hypotension increased the expression of both pERK and c-Fos protein in the NTS, which was abolished by pretreatment with glutamate receptor antagonists (MK801 or CNQX) in the MVN. Microinjection of glutamate receptor agonists (NMDA or AMPA) into the MVN increased the expression of both pERK and c-Fos protein in the NTS without causing changes in blood pressure. These results indicate that both NMDA and AMPA receptors play a significant role in the vestibulo-solitary projection of the VSR pathway for maintaining blood pressure, and that glutamatergic transmission in this projection might play a key role in the pathophysiology of orthostatic hypotension.

Pathways of Neurogenic and Humoral Control in the Vestibulosympathetic Reflex of Conscious Rats / 대한평형의학회지

OBJECTIVE: The vestibular system contributes control of blood pressure during postural changes through the vestibulosympathetic reflex. In the vestibulosympathetic reflex, afferent signals from the peripheral vestibular receptors are transmitted to the vestibular nuclei, rostral ventrolateral medullary nuclei, and then to the intermediolateral cell column of the thoracolumbar spinal cord. Physiological characteristics of the vestibulosympathetic reflex in terms of neurogenic and humoral control of blood pressure were investigated in this study. METHODS: Conscious rats with sinoaortic denervation were used for removal of baroreceptors in reflex control of blood pressure, and hypotension was induced by intravenous infusion of sodium nitroprusside (SNP). Expression of c-Fos protein was measured in the medial vestibular nuclei (MVN), rostral vestrolateral medullary nuclei(RVLM), and intermediolateral cell column (IMC) in T4-7, and levels of blood epinephrine were measured following SNP-induced hypotension. RESULTS: SNP-induced hypotension significantly increased expression of c-Fos protein in the MVN, RVLM, and IMC, also significantly increased level of blood epinephrine compared to normotensive control animals. CONCLUSION: These results suggest that the vestibulosympathetic reflex regulates blood pressure through neurogenic control including MVN, RVLM, and IMC, also through humoral control including epinephrine secretion by the adrenal medulla following SNP-induced hypotension. The physiological characteristics of the reflex may contribute to basic treatment of impairment of blood pressure control during postural changes.

Influence of betahistine on the expression of histamine H3 receptor in the medial vestibular nucleus following unilateral labyrinthectomy in guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To observe the influence of betahistine on the expression of histamine H3 receptor in the medial vestibular nucleus (MVN) following unilateral labyrinthectomy (UL).</p><p><b>METHODS</b>Fifty-six healthy guinea pigs were randomly divided into three groups:the sham-operated group (group I), the UL group[group II, and UL+betahistine (BET) group (group III)], BET was intraperitoneally injection at 2.17 mg×kg(-1)×d(-1) for 7 days. The expression of histamine H3 receptor was analyzed by immunohistochemistry at 1 day, 3 days and 7 days after UL.</p><p><b>RESULTS</b>H3 receptors were presented in the MVN and the expression of histamine H3 receptor were increased significantly in the ipsilateral MVN at 1 and 3 days after UL(P < 0.05), the change turned into the normal value at 7 days(P > 0.05). In the UL+BET group, the intensity of histamine H3 receptor was lower than that in the UL at 1 day and 3 days(4.25 ± 0.71, 3.50 ± 0.92 vs 5.75 ± 0.71, 5.50 ± 0.93, P < 0.05). However, the changes turned into the normal values at 3 and 7 days (P > 0.05).</p><p><b>CONCLUSIONS</b>The early stage of the vestibular compensation process may be associated with the change of H3 receptor expression in MVN. In the UL+BET group the histamine H3 receptor recovered quickly.</p>

Development of neural correlates of linear motion in the rat vestibular nucleus / 生理学报

The capability of the central vestibular system in utilizing cues arising from the inner ear determines the ability of animals to acquire the sense of head orientations in the three-dimensional space and to shape postural movements. During development, neurons in the vestibular nucleus (VN) show significant changes in their electrophysiological properties. An age-dependent enhancement of membrane excitability is accompanied by a progressive increase in firing rate and discharge regularity. The coding of horizontal and vertical linear motions also exhibits developmental refinement in VN neurons. Further, modification of cell surface receptors, such as glutamate receptors, of developing VN neurons are well-orchestrated in the course of maturation, thereby regulating synaptic efficacy and spatial coding capacity of these neurons in local circuits. Taken together, these characteristic features of VN neurons contribute to developmental establishment of space-centered coordinates within the brain.

The nucleus origin of acoustically evoked short latency negative response in guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>This study established a model of acoustically evoked short latency negative response (ASNR) in guinea pigs. Stereotaxic coordinate guided electrolytic lesion was applied to animal brainstem nuclei, the vestibular nucleus and the cochlear nucleus, to define the neural origin of ASNR.</p><p><b>METHODS</b>Twenty four guinea pigs with normal hearing were randomly divided into the control group (8 subjects, 16 ears) and the deafened group (16 subjects, 32 ears). Each animal experienced the auditory brainstem response (ABR) test. According to the presence of ASNR, the deafened group was further divided into ASNR group and non-ASNR group. Electrolytic lesion was conducted to the vestibular nucleus and cochlear nucleus respectively, followed by ABR test. The lesion structures were verified by brainstem slice and microscope.</p><p><b>RESULTS</b>In deafened group, the ASNR was elicited in 10 ears (31.3%). The ASNR was eliminated due to the electrolytic destruction to the vestibular nucleus, but it remained unchanged after the same procedure to the cochlear nucleus.</p><p><b>CONCLUSION</b>It is clear that the ASNR is originated from the vestibular nucleus, but not the cochlear nucleus.</p>

Anatomy and Physiology of Balance

Postural balance is controlled by intricate connections between the vestibular, visual and proprioception system. Among these, the vestibular system is one of the key factors in coordinating and maintaining balance. The peripheral apparatus for the vestibular system consists of the semicircular canals, which sense head rotation; and the otoliths, which sense gravity and linear acceleration. The central vestibular pathways form a large network from the vestibular nuclei, ocular motor nuclei, integration centers in the pons and rostral midbrain, vestibulocerebellum, thalamus, to the multisensory vestibular cortex areas in the temporoparietal cortex. The most important structures for the central vestibular pathways are those mediating the vestibulo-ocular reflex (VOR), and the descending pathways into the spinal cord along the medial and lateral vestibulospinal tract which mediate postural control. The cortical structures involved in vestibular function are the parietoinsular vestibular cortex, the retroinsular cortex, the superior temporal gyrus and the inferior parietal lobule. Activation of the cortical network during vestibular stimulation is not symmetrical; dominance is stronger in the nondominant hemisphere, in the hemisphere ipsilateral to the stimulated ear and in the hemisphere ipsilateral to the slow phase of the vestibular caloric nystagmus. Disorder of the vestibular pathway, anyway along its various tracts, may result in balance and coordination impairments and lead to misperception of motion.

Characterization of Membrane Excitability of Purkinje Cells in Vestibulocerebellum Using Patch Clamp Techniques / 대한이비인후과학회지

Cerebellum is known as a center for sensory/motor coordination and memory storage in motor learning. The vestibular nuclei have extensive afferent and efferent connections with posterior cerebellum which can be referred to as vestibulocerebellum. While secondary vestibular afferents are distributed bilaterally in the vestibulocerebellum, primary afferents may directly project to ipsilateral vestibulocerebellum. The Purkinje cells which are the only output neurons from the cerebellar cortex receive vestibular information via parallel and climbing fibers. That information is integrated and encoded in the Purkinje cells and then conveyed into the vestibular nucleus or deep cerebellar nucleus, which permits adaptive guidance of vestibular function by the vestibulocerebellum.

Pseudo-Vestibular Neuronitis Caused by Medial Vestibular Nucleus Infarction

No abstract available.

Expression of Metabotropic Glutamate Receptors in the Medial Vestibular Nucleus Following Acute Hypotension in Rats / 대한평형의학회지

BACKGROUND AND OBJECTIVES: Acute hypotension induces expression of c-Fos protein and phosphorylated extracellular signal-regulated kinase (pERK), and glutamate release in the vestibular nuclei. Expression of c-Fos protein and pERK is mediated by the excitatory neurotransmitter, glutamate. In this study, the signaling pathway of glutamate in the vestibular nuclei following acute hypotension was investigated. MATERIALS AND METHODS: Expression of metabotropic glutamate receptors (mGluRs) was measured by Western blotting in the medial vestibular nucleus following acute hypotension in rats. RESULTS: Expression of pGluR1 Ser831, a subtype of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, peaked at 30 minutes after acute hypotension insult, and expression of pNR2B, a subtype of N-methyl-D-aspartate (NMDA) receptors, peaked at 2 hours after acute hypotension insult. Acute hypotension induced expression of Homer1a and group I mGluR in the medial vestibular nucleus. Expression of mGluR1 and mGluR5 peaked at 6 hours following acute hypotension insults. CONCLUSION: These results suggest that afferent signals from the peripheral vestibular receptors, resulting from acute hypotension insult, are transmitted through group I mGluRs as well as AMPA and NMDA receptors in the vestibular system.