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Pathways of Neurogenic and Humoral Control in the
Vestibulosympathetic Reflex of Conscious Rats
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Guang Shi Jin, Gyoung Wan Lee, Sang Eon Park, Yuan Zhe Jin, Byung Rim Park
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Res Vestib Sci. 2015;14(4):110-116.
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 Abstract
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- 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.
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Role of the Cerebral Cortex on Vestibular Compensation Following
Unilateral Labyrinthectomy in Rats
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Hyun Kwang Ryoo, Seung Bum Yang, Min Sun Kim, Byung Rim Park
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Res Vestib Sci. 2015;14(3):75-82.
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Abstract
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- 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.
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Expression of Metabotropic Glutamate Receptors in the Medial Vestibular Nucleus Following Acute Hypotension in Rats
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Myoung Ae Choi, Nari Kim, Sang Eon Park, Byung Geon Park, Min Sun Kim, Byung Rim Park
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Res Vestib Sci. 2012;11(4):131-137.
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Abstract
- 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 α-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.
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Role of the Peripheral Vestibular End Organ in the Expression of c-Fos Protein in the Medial Vestibular Nucleus Following Occlusion of the Anterior Inferior Cerebellar Artery
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Nari Kim, Jae Hee Lee, Myoung Ae Choi, Byung Geon Park, Min Sun Kim, Byung Rim Park
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Res Vestib Sci. 2012;11(2):51-58.
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- Background and Objectives: The present study investigated the role of the peripheral vestibular end organ in vestibular symptoms and temporal changes in expression of c-Fos protein in the vestibular nuclei following anterior inferior cerebellar artery (AICA) occlusion using rats with unilateral or bilateral labyrinthectomy.
Materials and Methods: Expression of c-Fos protein in the vestibular nuclei was measured 2, 12, 24, and 48 hours after AICA occlusion.
Results: Unilateral AICA occlusion significantly induced expression of c-Fos protein bilaterally in the medial, inferior, superior, and lateral vestibular nuclei. Following AICA occlusion, the medial vestibular nucleus (MVN) showed the highest expression of c-Fos protein among the 4 vestibular nuclei. The expression of c-Fos protein was asymmetric between the bilateral MVN, showing higher expression in the MVN contralateral to the side of AICA occlusion compared to the ipsilateral MVN. The degree of asymmetry in c-Fos protein expression between the bilateral MVN peaked 12 hours after AICA occlusion. The expression of c-Fos protein gradually decreased 24 hours after AICA occlusion and returned to control levels 48 hours after AICA occlusion. Unilateral labyrinthectomy significantly decreased expression of c-Fos protein in the MVN ipsilateral to the side of labyrinthectomy following AICA occlusion. Moreover, bilateral labyrinthectomy significantly decreased expression of c-Fos protein in the bilateral MVN flowing AICA occlusion.
Conclusion: These results suggest that afferent signals from the peripheral vestibular end organ are crucial to the expression of c-Fos protein in the MVN following AICA occlusion and that expression of c-Fos protein is sustained for 24 hours after AICA occlusion.
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Application of Force Sensitive Resistors on Evaluation of Vestibulospinal Reflex Induced by Galvanic Stimulation
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Sang Eon Park, Jin Hee Park, Min Sun Kim, Ho Choon Jeong, Byung Rim Park
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Res Vestib Sci. 2011;10(3):92-99.
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Abstract
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- Background and Objectives: Force sensitive resistors (FSR) were used to measure the body sway to galvanic vestibular stimulation (GVS), and compared with the response obtained from force platform in normal subjects. Materials and Methods: Bipolar galvanic stimulation was applied to the bilateral mastoid process with intensity of 0.5-1.5 mA and duration of 1 sec in 3 different head positions of forward, rightward, and leftward. Results: Elevation of anterior pressure curve and depression of posterior pressure curve resulting from forward body sway were recorded in both feet by FSR. Forward body sway induced forward deviation of the center of pressure in force platform. Elevation of pressure curve in left foot and depression of the curve in right foot resulting from leftward body sway were recorded by FSR. Leftward body sway induced left deviation of the center of pressure in force platform. Orientation of the body sway induced by GVS was directed towards the anode side in the head facing forwards. Leftward and backward body sway resulting from cathodal stimulation on left mastoid process in leftward rotation of the head position and leftward and forward body sway resulting from cathodal stimulation on left mastoid process in rightward rotation of the head position were recorded by both FSR and force platform. Reaction time of GVS did not show any significant difference between FSR and force platform. Conclusion: These results indicate that FSR could be used to evaluate the vestibulospinal reflex to GVS.
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Understanding of Structure and Function of Vestibular Cortex
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Min Sun Kim, Jae Hee Lee, Gyoung Wan Lee, Byung Rim Park
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Res Vestib Sci. 2010;9(1):1-11.
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Abstract
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- The vestibular end-organs generate very sophisticated gravity sensory information about head movement by sensing head acceleration in three-dimensional space. Vestibular information is crucial for higher brain functions such as cognition of spatial orientation, spatial memory, and perception of self-motion. The term “vestibular cortex” represents cortical area where vestibular information is processed, converged with other sensory inputs to maintain cortical functions. The vestibular cortex gives rise to commend signals that control the vestibulosomatic reflex through the modulation of vestibular nuclear activity in the brainstem. The vestibular cortex includes such different cortical regions as the premotor region of the frontal cortex, parietal areas, temporal areas, and a central core region called parietoinsular vestibular cortex. This paper summarizes systemically animal and clinical research data concerned with the vestibular cortex in order to understand anatomy and functions of the vestibular cortex and to provide a basic literature for further study.
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Expression of Glutamate Receptors in the Medial Vestibular Nuclei following Acute Hypotension
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Jae Hee Lee, Myoung Ae Choi, Dong Ok Choi, Bo Kyoung Kim, Seok Min Hong, Byung Rim Park
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J Korean Bal Soc. 2007;6(1):29-35.
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Abstract
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- Acute hypotension induced excitation of electrical activities and expression of c-Fos protein and pERK in the vestibular nuclei. In this study, to investigate the excitatory signaling pathway in the vestibular nuclei following acute hypotension, expression of NR2A and NR2B subunits of glutamate NMDA receptor and GluR1 subunit of glutamate AMPA receptor was determined by RT-PCR and Western blotting in the medial vestibular nucleus 30 min after acute hypotension in rats. Acute hypotension increased expression of NR2A, NR2B, and pGluR1 in the medial vestibular nuclei. These results suggest that both of NMDA and AMPA glutamate receptors take part in transmission of excitatory afferent signals following acute hypotension.
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Unilateral Peripheral Vestibulopathy associated with Cerebral Venous Infarction
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Hyun Ah Kim, Hyung Lee, Byung Rim Park
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J Korean Bal Soc. 2006;5(2):285-287.
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- Cerebral venous infarction is associated with a wide variety of clinical symptoms and signs, which may often delay appropriate diagnosis. Unilateral vestibular deficit as a presenting sign of cerebral venous infarction has rarely been reported. We report a patient with cerebral venous infarction who had severe prolonged vertigo, vomiting, occipital headache, positive head thrust testing, and unilateral caloric weakness as main clinical features. Although the patient had occipital headache, overall symptoms and signs closely mimicked those of acute peripheral vestibulopathy.
Key Words : Peripheral vestibulopathy, Brain infarction
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Vestibular Neuritis of Vascular Cause
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Hyun Ah Kim, Hyung Lee, Byung Rim Park
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J Korean Bal Soc. 2006;5(2):277-280.
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Abstract
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- Vestibular neuritis (VN) is an idiopathic peripheral vestibular syndrome characterized by acute isolated prolonged vertigo. In most cases, it results from inflammation of the vestibular nerve presumably of viral origin. There has been no previous report of VN associated with a vascular cause. We here report a patient with VN of vascular origin who presented with acute onset of prolonged isolated vertigo, a unilateral decreased caloric response, and simultaneously with acute infarcts on brain MRI that were unrelated to patient's vertigo.
Key Words : Vestibular neuritis, Cerebral infarction
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Body Lateropulsion as an Isolated or Predominant Symptom of a Pontine Infarction
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Hyun Ah Kim, Hyung Lee, Byung Rim Park
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J Korean Bal Soc. 2006;5(2):224-228.
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Abstract
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- Background
and Objectives: Body lateropulsion with falling to one side is a well-known clinical feature of stroke in the posterior circulation. Body lateropulsion as an isolated or predominant manifestation of a pontine stroke has not previously been reported. To elucidate the possible mechanisms of patients presenting with body lateropulsion as an isolated or predominant symptom of isolated pontine infarction.
Materials and Method: Between May 2004 and February 2006, out of 134 admitted patients with an isolated pontine stroke we identified 8 consecutive patients (6.0%) in the Keimyung University Stroke Registry who had body lateropulsion as the main presenting symptom.
Results
All lesions were localized to the paramedian tegmentum just ventral to the 4th ventricle. All except 1showed a uniform pattern of body lateropulsion, in which the direction of falling was away from the side of infarct. In 2 patients, body lateropulsion was the sole clinical manifestation, whereas the other patients had other neurological signs. All but 1 had contraversive tilting of the subjective visual vertical (SVV). In all cases, the direction of SVV tilt corresponded to the direction of body lateropulsion. The mean net tilt angle was 6.1
Conclusion
Based on the known anatomy of ascending vestibular pathways, the SVV tilting, and MRI findings, body lateropulsion probably results from damage to the graviceptive pathway ascending through paramedian pontine tegmentum.
Key Words : Pons, Infarction
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Role of the Peripheral Vestibular System on Neuroplasticity Induced by Hypergravity Stimulation
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Jae Hyo Lee, Gyoung Wan Lee, Han Su Park, Jae Hee Lee, Dong Ok Choi, Myoung Ae Choi, Byung Rim Park
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J Korean Bal Soc. 2006;5(2):213-223.
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Abstract
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- Background
and Objectives: Altered environmental gravity, including both hypo- and hypergravity, may result in space adaptation syndrome. To explore the characteristics of this adaptive plasticity, the expression of immediate early gene c-fos mRNA in the vestibular system following an exposure to hypergravity stimulus was determined in rats.
Materials and Method: The animals were subjected to 2 G force (two-fold earth's gravity) stimulus for 3 hours, and were examined at post-stimulus hours 0, 2, 6, 12, and 24. Real time reverse transcription-polymerase chain reaction (RT-PCR) was adopted to analyze temporal changes in the expression of c-fos mRNA.
Results
The hypergravity stimulation produced the expression of c-fos mRNA in the vestibular ganglion, medial vestibular nucleus, inferior vestibular nucleus, hippocampus, vestibulocerebellum, and vestibular cortex. The peak expression occurred at hour 6 in the animals hypergravity-stimulated for 3 hours. Bilateral labyrinthectomy significantly attenuated the degree of up-regulation in c-fos mRNA expression. MK-801, an NMDA receptor antagonist, also significantly attenuated the degree of up-regulation in c-fos mRNA expression.
Conclusion
These results indicate that the adaptive neuroplasticity in response to an altered gravity occurs in the vestibular-related organs in the central nervous system, in which peripheral vestibular receptors and NMDA receptors play an important role.
Key Words : Hypergravity, Neuronal plasticity, Vestibule, c-fos gene
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Expression of Caveolin-1 in the Differentiated Vestibular Cell Line (UB/UE-1) after Gentamicin Toxicity
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Byung Han Cho, Kyu Sung Kim, Min Wook Kim, Min Sun Kim, Byung Rim Park
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J Korean Bal Soc. 2005;4(2):243-249.
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Abstract
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- Background
and Objectives: The caveolin is known as a mediator of cell death or survival of injured cell and inhibitor of various signaling pathways. We examined expression of caveolin-1 involved by protein kinase A(PKA) signaling pathway in the differentiated mouse vestibular cell line(UB/UE-1) after gentamicin toxicity.
Materials and Method: We observed caveolae in the vestibular hair cell of healthy guinea pig through electron microscope. UB/UE-1 cells were cultured at 95% CO2, 5% O2, 33℃ for 2days and at 95% CO2, 5% O2, 39℃ for 24 hours for differentiation. Cells were treated with 1 mM of gentamicin, 0.02 mM H89 (PKA inhibitor), and then incubated for 24 hours. Caveolin-1 expression was examined by western blot and PKA activity by PepTagⓇ assay.
Results
Caveolae were observed in the vestibular hair cell of healthy guinea pig by electron microscope. Caveolin-1 was expressed spontaneously in differentiated UB/UE-1 cells and increased after gentamicin treatment. PKA is overactivated by gentamicin treatment. The gentamicin induced caveolin-1 expression and PKA overactivation was inhibited by H89.
Conclusion
Our results indicate that gentamicin induced caveolin-1 expression is mediated by PKA signaling pathway. We conclude that the caveolae/caveolin through a PKA signaling pathway is the important mechanism of gentamicin induced ototoxicity.
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Role of Central Vestibular Pathway on Control of Blood Pressure During Acute Hypotension in Rats
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Yuan Zhe Jin, Guang Shi Jin, Min Sun Kim, Byung Rim Park
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J Korean Bal Soc. 2005;4(2):189-200.
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Abstract
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- Background
and Objectives: Central role of the vestibular system on control of blood pressure and interrelationships between the vestibular nucleus and solitary nucleus during acute hypotension were investigated in bilateral labyrinthectomized (BLX) or sinoaortic denervated (SAD) rats. Changes of electrical activity in the medial vestibular nucleus (MVN), solitary tract nucleus (STN), and rostral ventrolateral medullary nucleus (RVLM) were investigated in rats in while acute hypotension was induced by sodium nitroprusside (SNP).
Results
Evoked potential in MVN neuron caused by electrical stimulation of the peripheral vestibular system was composed of 3 waves with latencies of 0.48±0.10 ms, 1.04±0.09 ms and 1.98±0.19 ms. Electrical stimulation to MVN or RVLM increased blood pressure. MVN at the induction of acute hypotension showed excitation in 61% of type I neurons and inhibition in 68% of type II neurons. In STN, acute hypotension produced excitation in 62.1% of neurons recorded in intact abyrinthine animals, inhibition in 72.3% of neurons recorded in BL animals, and excitation in 60% of recorded neurons in SAD animals. In RVLM, acute hypotension produced excitation in 66.7% of neurons recorded in intact labyrinthine animals and inhibition in 64.9% of neurons recorded in BL animals. In spatial distribution of STN neurons responded to acute hypotension, excitatory responses were mainly recorded in rostral and ventral portion, and inhibitory responses were mainly recorded in caudal and lateral portion. In RVLM, excitatory responses were mainly recorded in rostral and dorsomedial portion, and inhibitory responses were mainly recorded in caudal and ventrolateral portion.
Conclusion
These results suggest that afferent signals from the peripheral vestibular receptors are transmitted to STN through the vestibular nuclei and assist to the baroreceptors for controlling blood pressure following acute hypotension.
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Otologic Causes of Drop Attacks in Elderly Patients
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Hyung Lee, Hyon Ah Yi, Jeong Geung Lim, Byung Hoon Ahn, Byung Rim Park
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J Korean Bal Soc. 2004;3(2):372-378.
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Abstract
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- Background
and Objectives : Many neurologists are unaware of the drop attack that may occur from an inner ear dysfunction especially in elderly. We performed this study to investigate the clinical features and results of quantitative audiovestibular tests in six elderly patients (≥65 years of age) who presented with drop attacks attributable to an inner ear pathology.
Materials and Method : Group was divided into Meniere's syndrome (4) or non-Meniere peripheral vestibulopathy (2). Standard dizziness questionnaire and quantitative audiovestibular function testing were performed.
Results
: Episodes were described as a sudden push to the ground in four or a violent illusionary movement of environment leading to a fall in two. All cases gave a history of prior vertiginous episodes and vestibular testing revealed unilateral caloric paresis. Ipsilateral hearing loss was documented in four cases.
Conclusions
: Our results suggest that otologic causes should be considered in the differential diagnosis of the drop attack in elderly, even if the symptoms and signs were not consistent with Meniere's syndrome.
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Immunohistochemical Identification of Phosphorylated Extracellular Signal-Regulated Kinase1/2 in Rat Vestibular Nuclei by Unilateral Labyrinthectomy
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Myoung Ae Choi, Dong Ok Choi, Kwang Yong Kim, Moon Young Lee, Byung Rim Park, Min Sun Kim
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J Korean Bal Soc. 2003;2(2):170-174.
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Abstract
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- This study evaluated the expression of phosphorylated signal-regulated kinase1/2 (pERK1/2), which is one of the main factors regulating transcription of the cfos oncogene in neurons, in the vestibular nuclei of Sprague-Dawley rats following unilateral labyrinthectomy (UL). Surgical UL was performed to eliminate afferent signals from the peripheral vestibular receptors in the inner ear, under a surgical microscope, 2 hours after anesthesia. Significant numbers of pERK1/2 immunoreactive neurons were seen in the superior, medial, and inferior vestibular nuclei. There were more pERK1/2 immunoreactive cells in the vestibular nuclei contralateral than in the vestibular nuclei ipsilateral to the injured labyrinth, which resulted in significant asymmetric expression of pERK1/2 immunoreactive cells. Subsequently, the pERK1/2 immunoreactivity decreased rapidly, disappearing 90 min after labyrinthectomy. No pERK1/2 labeling was seen in the lateral vestibular nucleus. These results suggest that intracellular signal pathways for the activation of extracellular signal-regulated kinase in the vestibular nuclei are involved in lesion-neural plasticity in the vestibular system.
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Effect of Ginkgo biloba on Expression of c-Fos Protein in the Vestibular Nuclear Complex following Unilateral Labyrinthectomy in Rats
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Dong Ok Choi, Sun Kyung Kim, Myung Ae Choi, Moon Young Lee, Min Sun Kim, Eun Ho Park, Byung Rim Park
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J Korean Bal Soc. 2003;2(2):163-169.
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Abstract
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- Background
and Objectives: The neuroprotective effect of Ginkgo biloba has been demonstrated in several in vivo and in vitro models. The effect of Ginkgo biloba on vestibular compensation following unilateral labyrinthectomy (UL) was investigated.
Material and Methods: Spontaneous nystagmus and c-Fos protein expression were measured following UL in Sprague-Dawley rats with pretreatment of Ginkgo biloba (50 mg/kg, i.p.).
Results
After pretreatment with Ginkgo biloba (50 mg/kg, i.p.) expression of c-Fos protein in the vestibular nuclear complex and frequency of spontaneous nystagmus were measured till 24 hours after UL. UL produced spontaneous nystagmus with frequency of 124±2.2 beats/min at post-op 2 hrs and 70±3.1 beats/min at post-op 24 hrs. Pretreatment with Ginkgo biloba significantly decreased the frequency of spontaneous nystagmus till post-op 24 hrs compared to control group (p<0.05). UL produced marked expression of c-Fos protein in bilateral medial vestibular nucleus, inferior vestibular nucleus, and superior vestibular nucleus, and the number of expression was significantly higher in contralateral vestibular nuclei to the lesion than ipsilateral vestibular nuclei at post-op 2 hrs (p<0.01). The number of c-Fos protein expression was decreased with time and significantly higher in ipsilateral vestibular nuclei than contralateral ones at post-op 24 hrs (p<0.01). Pretreatment with Ginkgo biloba significantly decreased the number of c-Fos protein expression following UL (p<0.01) and abolished the asymmetry of c-Fos protein expression in bilateral vestibular nuclei at post-op 24 hrs.
Conclusion
These results suggest that Ginkgo biloba may facilitate vestibular compensation following UL through modulation of neurotransmitters and neuroprotective effects.
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Spatio-temporal Changes on c-Fos Protein Expression in the Brain Stem Nuclei following Arsanilate-induced Unilateral Labyrinthectomy in Rats
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Jae Hyo Kim, Chang Ig Choi, Moon Young Lee, Min Sun Kim, Byung Soo Soh, Eun Ho Park, Byung Rim Park
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J Korean Bal Soc. 2003;2(1):86-94.
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Abstract
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- Spatio-temporal changes on c-Fos protein expression were investigated in vestibular compensation following unilateral labyrinthectomy (UL) induced by injection of arsanilate into the middle ear cavity, chemical labyrinthectomy, or surgical labyrinthectomy in medial vestibular nuclei (MVN), prepositus hypoglossal nuclei (PrH), and inferior olivary nuclei (ION) of Sprague-Dawley rats. Number of spontaneous nystagmus in surgical labyrinthectomy group was 28.2±1.2 beats/10 sec at post-op 2 hs and the nystagmus disappeared 76 hs after UL. In chemical labyrinthectomy group, spontaneous nystagmus occurred 6 hs after UL and increased up to maximum at 12 hs and disappeared 96 hs. Head deviation in surgical labyrinthectomy group reached a peak at post-op 2 hs and recovered to control level at 144 hs, but chemical labyrinthectomy produced head deviation 24 hs after UL and increased degree of the deviation over time till 144 hs. Expression of c-Fos protein in surgical labyrinthectomy group at post-op 2 hs was 81±19.4 cells in ipsilateral MVN to the lesion side and 212±60 cells in contralateral MVN, which showed severe asymmetry between bilateral MVN, and decrease of c-Fos protein expression was more in contralateral MVN than in ipsilateral MVN at 6 hs. Chemical labyrinthectomy expressed more c-Fos protein in contralateral MVN 6 hs after UL and in ipsilateral MVN 12 hs after UL, which showed asymmetry of c-Fos protein expression between bilateral MVN. And the expression in ipsilateral MVN of chemical labyrinthectomy group was increased gradually 48 hs after UL and reached a peak at 72 hs. In chemical labyrinthectomy group, expression of c-Fos protein in PrH was increased more in ipsilateral than in contralateral 6 hs after UL and more in contralateral 12 hs after UL, and ION showed more expression of c-Fos protein in contralateral than in ipsilateral 6 hs after UL through 72 hs. These results suggest that the course of vestibular compensation and the temporal expression of c-Fos protein in the brain stem nuclei following UL differed between surgical and chemical labyrinthectomy.
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Ionic mechanisms underlying spontaneous firing in isolated type B medial vestibular nucleus neurons
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Sang Woo Chun, Jeong Hee Choi, Kwon Soo Kim, Hyong Jae Lee, Seung Rok Kim, Moon Young Lee, Byung Rim Park
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J Korean Bal Soc. 2003;2(1):78-85.
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Abstract
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- Medial vestibular nucleus (MVN) neurons are found to have spontaneous electrical activity in the absence of any detectable synaptic input. To investigate the contributions of intrinsic mechanisms to the spontaneous activity of type B MVN neurons, we examined the effects of various channel blockers on spontaneous firing by means of patch clamp recordings. Coronal slice (400 ㎛) of the vestibular nucleus region was sequentially treated with pronase 0.2 ㎎/㎖ and thermolysin 0.2 ㎎/㎖, then single neurons were mechanically dissociated. MVN neurons recorded in neonatal rat were shown to have either a single deep afterhyperpolarization (AHP; type A cells), or an early fast and a delayed slow AHP (type B cells). In 300 nM TTX, spontaneous firing was blocked in type B cells tested. In 8 of 11 cells, underlying fluctuation or oscillations in membrane potential was not remained, and hyperpolarization did not produce rebound low-threshold calcium spikes. Although type B MVN neurons possessed hyperpolarization activated cation current (Ih), cesium had no effect on firing rates. The spike AHP is calcium dependent. When Ca2+ influx was blocked in external Ca2+ free solution, repetitive firing was abolished and the cell rested at depolarized embrane potentials. Application of apamin (300 nM) caused a profound reduction in the amplitude of the AHP and produced rhythmic burst firing. These findings suggest that the spontaneous activity of type B MVN neurons is regulated by interactions between the membrane depolarization mainly due to a ersistent sodium conductances and hyperpolarization due to the calcium-activated potassium conductances.
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Effect of vestibular end-organs on expression of cFos and FosB injury in the hippocampal formation of rats
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Min Sun Kim, Myoung Ae Choi, Dong Ok Choi, Byung Gon Cho, Yuan Zhe Jin, Jae Hyo Kim, Davy Kry, Byung Rim Park
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J Korean Bal Soc. 2002;1(2):223-234.
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Abstract
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- It is well known that the hippocampal formation requires primary vestibular sensory information to generate spatial memory during self motion in human. The purpose of the present study was to evaluate the effect of unilateral deafferentation of vestibular sensory information on cFos and FosB proteins, a family of immediate early gene-related proteins known as metabolic marker for neural excitation in the hippocampal formation of rats. Adult Sprague-Dawley rats weighing 250 - 300 g were surgically ablated of the peripheral vestibular system in the inner ear and sacrificed at 2, 6, 24, 48, 72 hours after surgical operation. Immunohistochemical staining and Western blot method were adapted to see change in expression of cFos and FosB proteins in the hippocampal formation. A significant change of Fos B immunoreactivity was observed in granular cell layer of the dentate gyrus, CA1 subfield of the hipocampus at 2 hours after unilateral labyrinthectomy. Thereafter, the number of FosB like immunoreactive neurons in these areas increased rapidly, peaked at 48 hours post operatively time. Western blot for FosB protein supported further time-dependent change of FosB revealed by immunohistochemical staining. In addition, granular cell layer showed more significant expression of FosB LI neurons in the caudal dentate gyrus than the rostral one. In contrast, moderate number of cFos LI neurons was detected in polymorphic cell layer of the dentate gyrus, pyramidal cell layer of CA1, and subiculum but not in granular cell layer of the dentate gyrus at 2 hours after labyrinthectomy. The number of cFos LI neurons in the hippocampal formation was rapidly decreased at 6 hours and then returned to basal value 24 hours after operation. These results suggest that unilateral ablation of the peripheral vestibular sensory information elicit spatio-temporal differences of cFos and FosB expressions in the hippocampal formation of rats.
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