Ménière's Disease and Electrophysiology / 대한평형의학회지

Inner ear is composed of cochlea, vestibule, and endolymphatic sac which are enclosed by thin layer of epithelial cells. The enclosed space is filled with fluid named as endolymph where the [K⁺] is high and [Na⁺] is low. This unique ion composition is very important in maintaining normal hearing and balance function by providing K⁺ ions into sensory hair cells, which finally depolarize hair cells to facilitate the transport of sound and acceleration stimulation to central nervous system. The ion composition of inner ear is maintained by various ion transport through ion channels, transporters, and exchangers in the inner ear sensory and extra-sensory epithelium. The disruption of normal endolymphatic ion composition by the deterioration of the function of those ion channels can cause dysfunction of sensory epithelium, which consequently results in hearing and balance disorders. One of the possible pathology from the disruption of inner ear ion homeostasis is endolymphatic hydrops which is a phenomenon of excessive fluid accumulation of inner ear. The dysfunction of ion channels in inner ear epithelium can be an etiology of Ménière's disease since endolymphatic hydrops is a main pathological finding of the disease. In this review, we discussed about the possible pathological mechanism of Ménière's disease as a perspective of channelopathy as well as the role of various ion channels in the regulation of inner ear fluid volume based on the findings revealed by electrophysiological studies.

A Case of Free-Floating Endolymph Particle Found during Transmastoid Posterior Semicircular Canal Occlusion for Intractable Posterior Canal Benign Paroxysmal Positional Vertigo / 대한이비인후과학회지

Benign paroxysmal positional vertigo (BPPV) is a common inner ear cause of vertigo, most of which can be treated by particle repositioning maneuver (PRM). However, in rare cases, positional vertigo could persist or frequently recur after several PRM. In these intractable cases, surgical treatments including singular neurectomy and semicircular canal occlusion have been used. Posterior semicircular canal occlusion has some advantages over singular neurectomy in hearing preservation and feasible surgical technique. Also free-floating endolymph particles causing intractable BPPV are known to occur in about 20% of the cases during canal occlusion surgery. Nevertheless, to the best of our knowledge, there has not been any report on the identification of those particles in the Korean literature. In this paper, we report a case of free-floating endolymph particle found during transmastoid posterior semicircular canal occlusion for intractable posterior canal BPPV.

Persistent Positional Vertigo in a Patient with Sudden Sensorineural Hearing Loss: A Case Report

Because inner ear organs are interconnected through the endolymph and surrounding endolymphatic membrane, the patients with sudden sensorineural hearing loss (SSNHL) often complain of vertigo. In this study, we report a patient with SSNHL accompanied by persistent positional vertigo, and serial findings of head-roll tests are described. At acute stage, head-roll test showed persistent geotropic direction-changing positional nystagmus (DCPN), which led to a diagnosis of SSNHL and ipsilateral light cupula. Although vertigo symptom gradually improved, positional vertigo lasted for more than 3 weeks. At this chronic stage, persistent apogeotropic DCPN was observed in a head roll test, which led to a diagnosis of the heavy cupula. Although the mechanism for the conversion of nystagmus direction from geotropic to apogeotropic persistent DCPN is unclear, the change of specific gravity of the endolymph might be one of the plausible hypothetical explanations.

Long-term efficacy of triple semicircular canal occlusion in the treatment of intractable Meniere's disease / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the long-term efficacy and safety of triple semicircular canal occlusion (TSCO) in the treatment of intractable Meniere's disease (MD) so as to provide an alternative surgical procedure for treating this disorder.</p><p><b>METHODS</b>Data from Forty-nine patients, who were referred to our hospital and diagnosed with unilateral MD strictly meeting the criteria issued by Chinese Academy of Otolaryngology-Head and Neck Surgery Committee (2006) from Dec. 2010 to Jul. 2012, were retrospectively analyzed in this work. Forty-nine patients, in whom the standardized conservative treatment was given at least one year and frequent vertigo still occurred, received TSCO. Vertigo control and auditory function were measured. Pure tone audiometry, caloric test, and cervical vestibular evoked myogenic potential (cVEMP) were performed for evaluation of audiological and vestibular function. Magnetic resonance hydrograph of inner ear was performed in patients received TSCO after 2 years for the observation of morphology of membranous labyrinth. Postoperative follow-up period was more than 2 years.</p><p><b>RESULTS</b>According to the preoperative staging of hearing, among these 49 patients, there were 2 cases in stage II (with an average hearing threshold of 25-40 dBHL), 40 in stage III (41-70 dBHL) and 7 in stage IV (over 70 dBHL). Vertigo was controlled effectively in all 49 cases in two-year follow-up, of which 40 cases (81.6%) were completely controlled and 9 cases (18.4%) were substantially controlled after surgery. The rate of hearing preservation was 69.4% and the rate of hearing loss was 30.6%. Post-operatively, all patients suffered from temporary vertigo and balance disorders. Vertigo was disappeared in all patients within 3-5 days, while averagely recovered after 13.5 days. Two years afer treatment, loss of semicircular canal function by caloric test was found in the operation side of all patients and no change in cVEMP test was noted. All patients had no facial paralysis, cerebrospinal fluid leakage, and other complications. Magnetic resonance hydrograph of inner ear showed that endolymph fluid in the position of plugging had no water after 2-years of TSCO.</p><p><b>CONCLUSIONS</b>TSCO, which can reduce vertiginous symptoms effectively in patients with intractable MD in long-term follow-up, represents an effective and safe therapy for this disorder. TSCO is expected to be used as an alternative procedure for the treatment of MD in selected patients suffering from severe hearing loss or recurrence after endolymphatic sac surgery.</p>

Relation between Stress-Related Hormone and Sudden Sensorineural Hearing Loss / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The plasma stress-related hormonal [cortisol, growth hormone, prolactin, antidiuretic hormone (ADH), adrenocorticotropic hormone (ACTH)] levels have been reported to be elevated in sudden sensorineural hearing loss (SSNHL) patients. However, little is known regarding the mechanisms related with the elevation of stress-related hormonal levels in SSNHL. Therefore, we measured the level of plasma stress-related hormones in SSNHL patients and in normal persons to demonstrate the association between the stress-related hormones and SSNHL. SUBJECTS AND METHOD: Stress-related hormonal levels were measured from 68 patients who were diagnosed with SSNHL. These values were compared with the stress-related hormonal levels of 24 healthy control subjects. RESULTS: The plasma ADH levels was significantly higher in SSNHL group compared with that in their normal control group, as shown by their respective values, 4.46 [95% confidence interval (CI): 3.80-5.24 pg/mL] and 3.05 (95% CI: 2.34-3.98 pg/mL). The values for plasma cortisol, growth hormone, and ACTH levels whose values were 2.07 (95% CI: 1.65-2.61 microg/L), 0.20 (95% CI: 0.14-0.29 microg/L), and 12.79 (95% CI: 11.16-14.66 pg/mL), respectively, were significantly lower in the SSNHL group than those in the normal control group whose values were 7.86 (95% CI: 5.33-5.24 microg/L), 0.61 (95% CI: 0.36-1.04 microg/L), 18.48 (95% CI: 14.99-22.78 pg/mL), respectively. But there was no significant difference in prolactin between the two groups. CONCLUSION: This study demonstrates a possible role of stress-related hormones in the pathogenesis of SSNHL. However, only ADH level was higher than the control group. Furthermore, ACTH, growth hormone and cortisol levels were lower than the control groups. This means ADH, growth hormone, cortisol, ACTH levels are related with SSNHL. However, the impact of this hormone on the inner ear and endolymph homeostasis is still unknown. Further investigation is necessary to identify the action mechanism of these hormones in the inner ear.

Visualization of endolymphatic hydrops in 3D-FLAIR MRI after intratympanic Gd-DTPA administration in Meniere's disease patients / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To study the feasibility of endolymphatic visualization and the diagnosis of Meniere's disease by applying intratympanic gadolinium administration through the tympanic membrance and three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI). To study the relationship between the endolymphatic hydrops visualized by MRI and audio-vestibular functional tests, such as pure tone audiometry (PTA), electrocochleography (EcoG), caloric test and vestibular evoked myogenic potential (VEMP).</p><p><b>METHODS</b>With a three Tesla magnetic resonance imaging (MRI) unit, 3D-FLAIR imaging was performed 24 hours after intratympanic gadolinium through the tympanic membrance in 32 patients with clinically diagnosed unilateral Meniere's Disease. We visualized the enhanced imaging of perilymphatic space in bilateral cochlea, vestibular and (or) canal, scoring scala tympani and scala vestibule of bilateral cochlear basal turn respectively and measuring the developing area of bilateral vestibule and the signal intensity ratio (SIR) between the vestibule and the brain stem subjectively. PTA, EcoG, caloric test and VEMP were performed. The relationship between the endolymphatic hydrops visualized by MRI and audio-vestibular functional tests were studied.</p><p><b>RESULTS</b>The gadolinium appeared in almost all parts of the perilymph in cochlea, vestibular and (or) canals in all 32 patients' inner ears, so the endolymphatic space was clearly shown on 3D-FLAIR imaging. The scala vestibuli score value between the affected side and the healthy side were statistically significant (Z = 4.309, P < 0.05) . The developing vestibular area between the affected side and the healthy side [(6.04 ± 2.89) mm(2), (8.28 ± 3.04)mm(2)] were statistically significant (t = 3.322, P < 0.05) . Abnormal vestibular evoked myogenic potentials were significantly correlated with the developing vestibular area of the affected side (F = 11.96, P < 0.05) . Abnormal electrocochleography were significantly correlated with scala vestibuli score value of cochlear basal turn in the affected side (Z = 3.17, P < 0.05) . No significant correlation was found between the scala vestibuli score value or the developing vestibular area and caloric test or PTA findings.</p><p><b>CONCLUSIONS</b>3D-FLAIR MRI with intratympanic gadolinium injection through the tympanic membrance can discriminate the border between the perilymph and the endolymph and show endolymphatic hydrops. This method may provide radiographic reference for the diagnosis of Meniere's disease. The results of VEMP and electrocochleography might have appropriate correlation with degree of vestibular and cochlear hydrops.</p>

Utility of Sp/Ap curve area ratio electrocochleography in diagnosis of Meniere's disease / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#Comparison of the sensitivity of Sp/Ap amplitude and area ratio in the aid of diagnosis of Meniere's disease. Meniere's disease was defined by the 1995 American Academy of Otolaryngology-Head and Neck Surgery Committee on Hearing and Equilibrium.@*METHOD@#The study sample consisted of 35 patients in our hospital, who were undergone tympanic electrocochleography (EcochG). A control group of 10 patients (20 ears) with normal Sp/Ap ratio and EcochG data were identified. Sp/Ap amplitude and area curve ratios for both group were measured.@*RESULT@#The traditional upper limit and the upper limit of normal for Sp/Ap amplitude and area curve were respectively 0.4, 46 and 1.94. Of 35 patients with Meniere's disease, had an abnormal Sp/Ap amplitude ratio,and had an abnormal Sp/Ap area curve ratio; the difference between groups was statistically significant.@*CONCLUSION@#Sp/Ap curve area curve ratio is more sensitive than conventional Sp/Ap amplitude ratios in diagnosis of Meniere's disease.

Influences of two different endolymphatic infusion ways to cochlear morphology and function in guinea pigs / 中华耳鼻咽喉头颈外科杂志

<p><b>OBJECTIVE</b>To explore the influence of two different endolymphatic infusion ways on cochlear morphology and function.</p><p><b>METHODS</b>Forty healthy pigment guinea pigs (250 - 350 g) with normal Prey's reflex were divided into A and B group with 20 animals respectively. The right ears served as treated ears and the left ones as control ones. In group A, 5 microl of adenovirus 5-enhanced green fluorescence protein (Ad5-EGFP) suspension was infused into the scala media through an opened cochleostomy on the lateral wall of the scala media (LWS). In group B, the same volume of Ad5-EGFP suspension was infused into the scala media through punctured round window membrane and the basilar membrane (RBM). Cochlear morphology was examined under scan electric microscope and phalloidin staining was used to observe the hair cells in the infused ears after the animals were sacrificed. Auditory brainstem thresholds of the ears of all the animals were measured before and after treatment.</p><p><b>RESULTS</b>All the animals recovered well after operation. The holes on the lateral wall of the scala media and punctures on the round window membrane were healed completely. EGFP labeling appeared in the organ of Corti and lining wall of the stria vascularis indicated that adenovirus suspension was injected into the scala media using LWS (succeed in 14 animals accounted for 70%) and RBM (in 8 animals accounted for 40%) ways. Viruses were inoculated into the scala media with only locally inflammation reaction. In group A the hearing threshold decreased significantly in the treated ears compared with the control ears after the operation [(33.1+/-10.3) dB, (9.4+/-3.9) dB, F=46.34, P=0.0005]. However, in group B there was no significantly different between the treated ears and the control ears after the operation [(2.5+/-3.8) dB, (2.5+/-3.8) dB, F=0.00, P=1.000]. Phalloidin staining indicated that in group A the extension of hair cells loss was bigger than in group B. In some animals of two groups, EGFP labeling appeared in the extra-lymphatic system indicating that some of the injected suspension leaked out of the scala media.</p><p><b>CONCLUSIONS</b>Ad5-EGFP could be infused into the scala media through LWS or RBM and adenovirus could infect the lining cells of scala media and supporting cells in the basal membrane successfully without causing immunoreaction in the whole cochlea. LWS caused more hair cell loss and hearing loss than RBM. However, the cochlear morphology could be recovered completely after surgery. The positive inoculation rate was relatively higher that through LWS than that through RBM.</p>

Expression Patterns of KCNJ10 K+ Channel in the Cochlear Lateral Wall After Acoustic Trauma / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: It is well known that noise exposure leads to the sensory hair cell loss and other neuronal damage in the cochlea. But recently it has been reported that noise exposure could also damage lateral wall of cochlea such as stria vascularis and spiral ligament. K+ is the major cation in endolymph and important to maintain homeostasis within the cochlea. We have investigated the expression patterns of KCNJ10 K+ channel in noise induced cochlear damage. MATERIALS AND METHOD: Twenty adult male guinea pigs (300-350 g) were included in this study. In experimental group (n=16), acoustic trauma was induced by continuous broad band noise for 2 hr to 115 dB SPL and broad band noise for 6 hr to 120 dB SPL with 3 consecutive days. After noise exposure, auditory brainstem response threshold shift and hair cell loss were evaluated. A study for KCNJ10 K+ channel expression was examined by immunohistochemical staining. RESULTS: After noise exposure, auditory brainstem response showed transient threshold shift (TTS) and permanent threshold shift (PTS) in accordance with noise exposure. The expression patterns of CKNJ10 K+ channel were changeable in TTS group. But there were no change of expression patterns in PTS group. CONCLUSION: In the cochlear lateral wall, KCNJ10 K+ channel expressions were affected with noise exposure and these changes might be associated with the regulation of homeostasis in the cochlea lateral wall.

Meniere's Disease

Hydrops of the endolymphatic space in the inner ear deteriorates hearing and balance function. This idiopathic syndrome of endolymphatic hydrops is Meniere's disease and is characterized by episodic vertigo, fluctuating hearing loss, tinnitus and ear fullness. For the pathophysiologic mechanisms of the episode, the progression of the hydrops leads to ruptures in the membranes separating endolymph from perilymph, producing a sudden increase in potassium concentration in the perilymph. Recurrent episodes may interfere with routine daily activities and sometimes accompany sudden drop attacks, so called Tumarkin's otolithic crisis, which may lead to serious injuries. Life style modification, low salt diet and prescription of diuretics have been traditionally tried in order to relieve endolymphatic hydrops. Surgical and destructive treatment options are necessary in selected intractable patients depending on the frequency of vertigo, severity of hearing loss and the possibility of bilateral involvement. However, a large proportion of these patients shows a spontaneous cure of vertigo with the aggravation of hearing loss (burnt out stage) over time. The goal of treatment is trying not to make the patient worse than this natural course of disease.

The Role of Inflammatory Mediators in the Pathogenesis of Otitis Media and Sequelae

This review deals with the characteristics of various inflammatory mediators identified in the middle ear during otitis media and in cholesteatoma. The role of each inflammatory mediator in the pathogenesis of otitis media and cholesteatoma has been discussed. Further, the relation of each inflammatory mediator to the pathophysiology of the middle and inner ear along with its mechanisms of pathological change has been described. The mechanisms of hearing loss including sensorineural hearing loss (SNHL) as a sequela of otitis media are also discussed. The passage of inflammatory mediators through the round window membrane into the scala tympani is indicated. In an experimental animal model, an application of cytokines and lipopolysaccharide (LPS), a bacterial toxin, on the round window membrane induced sensorineural hearing loss as identified through auditory brainstem response threshold shifts. An increase in permeability of the blood-labyrinth barrier (BLB) was observed following application of these inflammatory mediators and LPS. The leakage of the blood components into the lateral wall of the cochlea through an increase in BLB permeability appears to be related to the sensorineural hearing loss by hindering K+ recycling through the lateral wall disrupting the ion homeostasis of the endolymph. Further studies on the roles of various inflammatory mediators and bacterial toxins in inducing the sensorineumral hearing loss in otitis media should be pursued.

Endolymphatic visualization in patients with Meniere's disease / 中国医学科学院学报

<p><b>OBJECTIVE</b>To attempt to visualize the endolymph in patients with Meniere's disease by applying non-invasive intratympanic gadolinium through eustachian tube and three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging (3D-FLAIR MRI).</p><p><b>METHODS</b>With a 3 Tesla magnetic resonance imaging (MRI) unit, 3D-FLAIR imaging was performed 24 hours after intratympanic gadolinium through eustachian tube in two patients with medically active and intractable Meniere's disease. Pure tone test and tympanometry were performed 24 hours before and after the administration of gadolinium.</p><p><b>RESULTS</b>The gadolinium appeared in almost all parts of the perilymph inside the inner ear; moreover, the border between the perilymph and the endolymph was visible so endolymphatic space was clearly shown on 3D-FLAIR. No change in pure tone test and tympanometry was noted.</p><p><b>CONCLUSIONS</b>3D-FLAIR MRI with intratympanic gadolinium through eustachian tube can clearly reveal the visualization of endolymph in patients with Meniere's disease. Intratympanic gadolinium therapy through eustachian tube is a safe and effective.</p>

A Case of Congenital Sensorineural Hearing Loss with Multinodular Goiter / 대한이비인후과학회지

Pendred syndrome is an autosomal recessive condition classically characterized by congenital deafness and goiter, and is the most common cause of hereditary deafness in Korea. It is caused by mutations in the PDS gene (SLC26A4) located in 7q31. The PDS gene encodes a chloride-iodide transport protein called pendrin, which plays a role in the reabsorption of endolymph and the maintenance of the endolymph homeostasis in the inner ear and in the uptake and organification of iodide in the thyroid gland. A mutation in PDS also causes non-syndromic recessive deafness (DFNB4) and therefore securing the diagnosis is important for genetic counseling purposes. The perchlorate discharge test and radiological conformation of the inner ear anomaly are useful diagnostic aids but have limited diagnostic value. However, because PDS mutations are widely distributed along the gene, it consumes too much time and money to perform molecular studies in clinics. We present a case of congenital sensorineural hearing loss with multinodular goiter, which shows definite findings of Pendred syndrome.

Morphological Changes of Endolymphatic Sac after Gentamicin Injection to Chick Embryo / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Gentamicin, which is known to have potential toxic effect to the inner ear, causes functional disturbance by destroying the inner ear at a concentration above a certain level. The purpose of this study was to identify morphological changes in the endolymphatic sac after gentamicin injection using chick embryo and the degree of changes according to different concentration of gentamicin. MATERIALS AND METHOD: The same breed of chicken (Gallus domesticus) was chosen and artificial growth incubator was used to germinate the eggs. Increasing the concentration of gentamicin at the same rate (10, 20, 30, 40 mg/ml), we injected it into the yolk sac of chicken and observed the morphological changes in the embryonic sac by light microscope. RESULTS: As the concentration of gentamicin increased, the size of the endolymphatic sac increased and the thickness and contour of sac wall changed. Especially, the inner membrane thinned down greatly. CONCLUSION: In this research, we confirmed that endolymphatic sac is affected by gentamicin in proportion to its concentration. Especially, considering that inner membrane epithelial cells play an important role in the absorption of endolymph, we suggest that the ototoxicity of gentamicin causes the disturbance in the absorption of endolymph, which may cause endolymphatic hydrops.

Firing properties and classification of MVN neurons in rats / 华中科技大学学报（医学）（英德文版）

In order to know the effects of caloric stimulation on neuronal firing in medial vestibular nuclei (MVN) by middle ear irrigation, the middle ear was irrigated with ice (4 degrees C), hot (44 degrees C), and warm (37 degrees C) water, and the firing rate of MVN neuron was extracellularly recorded. The results showed that the firing rate of MVN neuron was changed by caloric stimulation, and the majority of MVN neurons showed excitation by irrigation with hot water and inhibition by ice water (type A). The neuronal firing was recovered immediately after the cessation of the stimulation. I It was concluded that the neuronal firing rate in MVN was changed by caloric stimulation in middle ear cavity. The response was different in various neurons.

Firing properties and classification of MVN neurons in rats / 华中科技大学学报（医学）（英德文版）

In order to know the effects of caloric stimulation on neuronal firing in medial vestibular nuclei (MVN) by middle ear irrigation, the middle ear was irrigated with ice (4 degrees C), hot (44 degrees C), and warm (37 degrees C) water, and the firing rate of MVN neuron was extracellularly recorded. The results showed that the firing rate of MVN neuron was changed by caloric stimulation, and the majority of MVN neurons showed excitation by irrigation with hot water and inhibition by ice water (type A). The neuronal firing was recovered immediately after the cessation of the stimulation. I It was concluded that the neuronal firing rate in MVN was changed by caloric stimulation in middle ear cavity. The response was different in various neurons.

Expression of Protein Kinase C Isotypes in the Albino Guniea Pig Cochlea / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Protein kinase plays an important role in transmembrane signalling, which is modulated by cellular transduction by second messengers such as inositol-1, 4, 5-triphosphate (IP3), Diacylglycerol (DG), cAMP, to express biological activity by stimulation of hormones, neurotransmitters, antigens, growth factors. Protein kinase Cs participate in signal transduction of cell, secretion of neurotransmitter, regulation of ion conduction, exocytosis, gene expression and cellular proliferation. Also, it raises slow motility by Na+-H+ exchange (NHE) and Ca2+ channel in the outer hair cells. It may also be involved in mechanical transduction, cellular proliferation and reproduction in supporting cells, and in producing endolymphs using the KCNE1 and Na+/K+-ATPase in the lateral wall of cochlea. MATERIALS AND METHOD: We investigated the immunoreactivities of the PKC (alpha, beta, gamma, delta) via paraffin section and surface preparation of the cochlea of albino guinea pigs. RESULTS: PKC alpha immunoreactivities were shown in the outer and inner hair cell cytoplasm and delta was revealed in the type II fibrocytes and suprastrial cells in the basal turn of the spiral ligament. But beta, gamma were not shown. CONCLUSION: We suggest that PKC alpha may induce the slow motility and depolarization to mediate the ion conductance in the hair cells. Also, PKC delta may participate in the production of endolymph. We thus conclude that PKC alpha and delta play an important role in the cochlear signal transduction.

Prophylactic effect of Ca2+ -deficient artificial perilymph perfusion on noise-induced hearing loss / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the prophylactic effect of low calcium concentration perilymph on noise-induced hearing loss.</p><p><b>METHODS</b>Forty guinea pigs with normal hearing weighing 250-350 g were assigned to five groups (8 in each group): (1) Ca(2+)-deficient perilymph perfusion (CDP) for 2 h; (2) white noise (120 dB SPL) exposure (WNE) only for 1 h, (3) combination of calcium-deficient perilymph perfusion and white noise (120 dB SPL) exposure (WNE + CDP); (4) normal artificial perilymph (NAP) perfusion for 2 h; and (5) white noise exposure + normal artificial perilymph perfusion (WNE + NAP) for 2 h. Compound action potentials (CAP) evoked by click was recorded from round window every 15 min. The cochleae from 5 animals in each group were examined with scanning electron microscope.</p><p><b>RESULTS</b>The CAP for group 1 experienced a threshold shift (TS) of 15-26 dB, while group 2 yielded a 46-59 dB TS and group 3 a 37-45 dB TS; no threshold shift occurred in group 4. The CAP TS in group 5 was 33-64 dB. The CAP TS of group 3 was less than that of group 2. After one hour of noise exposure, the CAP TS of group 3 were 45.92 +/- 2.90 dB and 59.30 +/- 3.95 dB in group 2. There were significant differences (P < 0.05) between groups 3 and 2. The CAP TS of group 3 was less than that of group 5 at the points of 1, 1.5 and 2 h after noise exposure. There was a significant difference between groups 3 and 5 (P < 0.01). Stereocilia of 89 OHC(3) were in disarray in five cochleae after noise exposure in group 2. The cuticular plates of 8 OHC(2),3 sank and the stereocilia became fused in only one animal cochlea after noise exposure in group 3 combined with low calcium perilymph perfusion.</p><p><b>CONCLUSIONS</b>Low calcium concentration appears to participate in preventing noise-induced hearing loss and the rising of calcium concentrations in inner hair cells after noise exposure, which may have been due to the opening of calcium channels in inner hair cells during noise exposure. The mechanism of the prophylactic effect might be caused by a lower calcium concentration in inner hair cells in the cochlea attenuating the influence of noise exposure on hearing loss; calcium deficient perilymph perfusion prevented calcium accumulation in inner hair cells of the cochlea. The motility of the OHCs might be partially inhibited by low calcium concentration that reduced noise-induced hearing loss in turn.</p>

Expression of Voltage-dependent Na+ Channels in the Albino Guinea Pig Cochlea / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The endolymph produced from cochlear lateral wall regulates fluid and maintains positive endocochlear potential. Although many immunohistochemical studies of ion transport enzymes in the cochlear lateral wall have been reported, their mechanisms are still not completely understood. And there are no reports on the studies of anti-Na+ channels in the cochlea of the guinea pig. The voltage-dependent ion channels are fundamental components of neuronal activity. The Na+ channel has a single alpha subunit with 4 pseudosubunits of 6 transmembrane segments each. Expression of the pore-forming and voltage-sensing alpha or alpha1 subunit typically leads to the appearance of channels with voltage- and time-dependent gating and ion conductance. The purpose of this study is to evaluate the expression of the Na+ channel type I and II in the cochlea lateral wall. MATERIALS AND METHODS: We investigated the protein identification by western blot after homogenization and immunohistochemical localization by FITC to the anti-Na+ channel type I and II in the cochlea of the Preyer's positive, white guinea pigs. RESULTS: The results showed that the anti-Na+ channel type I and II were expressed strongly in the intermediate cells of the stria vascularis, and weakly in the stria vascularis. CONCLUSION: We suggest that there are voltage-dependent Na+ channels in the stria vascularis of cochlea and those functions are further evaulated physiologically by the patch clamp technique.

Immunohistochemical Localization of Na/K-APTase Subunit Isoforms in Rat Inner Ear / 대한해부학회지

The endolymph and perilymph of the inner ear have unique ionic composition and electrical potential. It is widely accepted that normal auditory function depends on them and Na/K-ATPase plays a central role in production and maintenance of them. The distribution of five Na/K-ATPase subunit isoform (alpha1, alpha2, alpha3, beta1, and beta2) in rat inner ear was determined by immunohistochemistry after decalcifying the temporal bone with Gooding and Stewart's solution. In the cochlear regions, Na/K-ATPase alpha1beta1 isozyme was abundantly expressed in the infrastrial fibrocytes, suprastrial fibrocytes, spiral prominence, outer sulcus cells and spiral ganglion, and also detected in cochlear nerve and interdental cells. alpha1beta2 isozyme was abundantly expressed in all layers of stria vascularis and alpha3beta1 isozyme was detected in cochlear nerve and spiral ganglion. alpha3beta2 isozyme was expressed in spiral ganglion. In vestibular regions, Na/K-ATPase alpha1b1 isozyme was expressed in macular sacculi hair cell, transitional cells of ampulla, and vestibular ganglion, and alpha1b2 isozyme was abundantly expressed in ampullary dark cells and transitional cells and vestibular ganglion. a3b1 isozyme was abundantly expressed in crista ampularis, macula utriculi, and macula sacculi hair cells, and also moderately detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. alpha3beta2 isozyme also detected in ampullary, utricular, and saccular nerves, and vestibular ganglion. But, alpha2beta1 and alpha2beta2 isozymes were not detected in any regions of inner ear. These findings suggest the possibility of four unique Na/K-ATPase isozymes deferentially expressed among the various cell types of the inner ear. This structural diversity imparts considerable biological versatility to the Na/K-ATPase and would be provided the explanations for the differences in fluid and ion transport and its regulation among the inner ear regions.