BACKGROUND AND OBJECTIVES: The purpose of this study was to investigate the effects of low level laser for the prevention and treatment of aminoglycoside-induced vestibular ototoxicity. MATERIALS AND METHOD: An organotypic culture of 2 to 4 days old rat utricular maculae was established. Rats were divided into 6 groups according to the treadtment of the utricles: G (gentamicintreated), L (laser-irradiated), LG (laser-irradiated and gentamicin-treated), GL (gentamicin-treated and laser-irradiated), LGL (gentamicin-treated during laser-irradiated) and C (control). After organotypic culture, the utricles of 6 groups were examined by confocal laser scanning electron microscope and scanning electron microscope. The results of each group were compared with each other by statistical methods. RESULTS: The number of vestibular hair cells of the group G was smaller compared to that of the group C. The group L had no difference compared with the group C. The groups LG and GL showed more vestibular hair cells compared with the group G. The group LG showed more vestibular hair cells than the group GL. The group LGL showed most vestibular hair cells compared to that of the groups G, LG, and GL. CONCLUSION: The most effective treatment of aminoglycosideinduced vestibular otoxicity is the irradiation of low level laser before and after the insult of the aminoglycoside. Further clinical studies using low level laser were needed to prevent aminoglycoside-induced ototoxicity and to promote the regeneration of vestibular hair cells.
Animals ; Electrons ; Gentamicins ; Hair Cells, Vestibular ; Rats ; Regeneration ; Saccule and Utricle

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.
Blood Pressure* ; Dizziness ; Ear, Inner ; Epinephrine ; Glutamic Acid ; Hair Cells, Vestibular ; Hypotension* ; Reflex ; Vestibular Nuclei

BACKGROUND AND OBJECTIVES: To culture and maintain mammalian hair cells is still a big challenge. In this study, long-term organotypic culture of rat utricular maculae was established to study vestibular hair cell. The effects of low level laser on hair cell viability in postnatal organotypic culture of rat utricles were investigated. MATERIALS AND METHOD: Uticular explants were prepared from postnatal 2 to 7 rats and cultured. To improve hair cell survival, the utricles were irradiated daily with low level laser. Whole-mount utricles were stained with FM1-43 which is known to be an efficient marker to identify live hair cells in cultured tissues. Such cells visualized directly through tissue culture dish with cover glass bottom by Confocal laser scanning microscope at specific time points. RESULTS: The explanted utricular hair cells were cultured for up to 31 days in in vitro culture system. In low level laser irradiation group, utricular hair cells were more survived at 24 DIV and 31 DIV. CONCLUSION: These results suggest that low level laser promotes hair cell viability in utricular explants.
Animals ; Cell Survival* ; Glass ; Hair Cells, Vestibular ; Hair* ; Rats* ; Saccule and Utricle*

BACKGROUND AND OBJECTIVES: To culture and maintain mammalian hair cells is still a big challenge. In this study, long-term organotypic culture of rat utricular maculae was established to study vestibular hair cell. The effects of low level laser on hair cell viability in postnatal organotypic culture of rat utricles were investigated. MATERIALS AND METHOD: Uticular explants were prepared from postnatal 2 to 7 rats and cultured. To improve hair cell survival, the utricles were irradiated daily with low level laser. Whole-mount utricles were stained with FM1-43 which is known to be an efficient marker to identify live hair cells in cultured tissues. Such cells visualized directly through tissue culture dish with cover glass bottom by Confocal laser scanning microscope at specific time points. RESULTS: The explanted utricular hair cells were cultured for up to 31 days in in vitro culture system. In low level laser irradiation group, utricular hair cells were more survived at 24 DIV and 31 DIV. CONCLUSION: These results suggest that low level laser promotes hair cell viability in utricular explants.
Animals ; Cell Survival* ; Glass ; Hair Cells, Vestibular ; Hair* ; Rats* ; Saccule and Utricle*

BACKGROUND AND OBJECTIVES: In normal postnatal mammalian inner ear sensory epithelium, regeneration of hair cells is a very rare event, but there is hair cell regeneration with partial restoration of the vestibular sensory epithelium following ototoxic damage. In this study, the effects of low-level laser on hair cell regeneration following gentamicin exposure in postnatal organotypic culture of rat utricles were investigated. MATERIALS AND METHOD: A long term organotypic culture of 2 to 7 day old rat utricular maculae was established to study aminoglycoside-induced vestibular hair cell renewal. The utricles were exposed to 1 mM of gentamicin for 48 hr and allowed to recover in a culture medium only or in a medium with daily irradiation of low-level laser, whereas the control group was not exposed to gentamicin. Whole-mount utricles were stained with FM1-43, which are known to be an efficient marker, to identify live hair cells in cultured tissues. RESULTS: Loss of hair cells was nearly stopped from 2 days after exposure to gentamicin ; a peak of regeneration was reached after 18 days and sustained for two weeks in the medium with the irradiation of low-level laser. CONCLUSION: These results suggest that low-level laser promotes spontaneous hair cell regeneration following gentamicin damage in utricular explants.
Animals ; Ear, Inner ; Epithelium ; Gentamicins* ; Hair Cells, Vestibular ; Hair* ; Rats* ; Regeneration* ; Saccule and Utricle*

The basic mechanism for the excitation of the peripheral vestibular receptors following acute hypotension induced by sodium nitroprusside (SNP) or hemorrhage was investigated in anesthetized rats. Electrical activity of the afferent vestibular nerve was measured after pretreatment with kynurenic acid, an NMDA receptor antagonist. The activity of the vestibular nerve at rest following acute hypotension induced by SNP or simulating hemorrhage was a greater increase than in control animals. The gain of the vestibular nerve with sinusoidal rotation following acute hypotension increased significantly compared to control animals. The acute hypotension induced by SNP or hemorrhage did not change the activity of the afferent vestibular nerve after kynurenic acid injection. These results suggest that acute hypotension produced excitation of the vestibular hair cells via glutamate excitotoxicity in response to ischemia.
Animals ; Glutamic Acid ; Hair Cells, Vestibular ; Hemorrhage ; Hypotension* ; Ischemia ; Kynurenic Acid ; N-Methylaspartate ; Nitroprusside ; Rats* ; Vestibular Nerve*

Bilateral loss of vestibular sensation from injuries of vestibular hair cells causes individuals suffering poor vision during head movement, postural instability, chronic disequilibrium, and cognitive distraction. A vestibular prosthesis analogous to cochlear implants but designed to modulate vestibular nerve activity during head movement should improve quality of life for these chronically dizzy individuals. An implantable prosthesis that partly restores normal activity on branches of the vestibular nerve should improve quality of life for individuals disabled by this disorder. There have been many efforts to develop and restore 3-dimensional angular vestibule-ocular reflex and the Johns Hopkins vestibular neuro-engineering laboratory has been developing a head-mounted multichannel vestibular prosthesis that restores sufficient semicircular canal function to partially recreate a normal 3-dimensional angular vestibulo-ocular reflex. In this review, their results are described.
Cochlear Implants ; Dizziness ; Ear, Inner ; Hair Cells, Vestibular ; Head Movements ; Prostheses and Implants ; Quality of Life ; Reflex ; Reflex, Vestibulo-Ocular ; Semicircular Canals ; Sensation ; Stress, Psychological ; Vestibular Nerve ; Vision, Ocular

OBJECTIVETo investigate the ototoxic effects of streptomycin in vestibular organotypic cultures.

METHODSF344 rats with age at postnatal day three or four were used for this study. The maculae of saccule and utricle were routinely dissected out and cultured with serum-free medium containing various dose of streptomycin for 24 hours. The ciliary turf of vestibular hair cells was stained with fluorescent phalloidin, and its nucleus was stained with to pro-3 DNA probe. The vestibular hair cells were quantitatively counted and photographed under confocal fluorescent microscope.

RESULTSMorphological feature of vestibular hair cells were good in normal control cultures. However, the density of hair cells was decreased in evidence with increase of streptomycin sulfate concentrations. Twenty-four hours after streptomycin cultures, 0.25 mmol/L streptomycin caused a 10% hair cell missing, 50% hair cell loss from 1 mmol/L streptomycin treatment, and more than 75% hair cells gone post-3 mmol/L streptomycin cultures. After streptomycin treatment, the nuclear shrinkage and fragmentation were found in vestibular hair cells, whereas the vestibular supporting cells were normal.

CONCLUSIONStreptomycin induced-vestibular hair cells lesion was in a dose dependent manner with nuclear shrinkage and fragmentation. This may suggest that streptomycin leads vestibular hair cell die through apoptosis.

Animals ; Apoptosis ; drug effects ; Hair Cells, Vestibular ; cytology ; drug effects ; Organ Culture Techniques ; Rats ; Rats, Inbred F344 ; Streptomycin ; adverse effects

OBJECTIVETo explore the mechanisms of the influx of calcium ions during the activation of ACh-sensitive BK channel (big conductance, calcium-dependent potassium channel) in type II vestibular hair cells of guinea pigs.

METHODSType II vestibular hair cells were isolated by collagenase type IA. Under the whole-cell patch mode, the sensitivity of ACh-sensitive BK current to the calcium channels blockers was investigated, the pharmacological property of L-type calcium channel activator-sensitive current and ACh-sensitive BK current was compared.

RESULTSFollowing application of ACh, type II vestibular hair cells displayed a sustained outward potassium current, with a reversal potential of (-70.5 +/- 10.6) mV (x +/- s, n = 10). At the holding potential of -50 mV, the current amplitude of ACh-sensitive potassium current activated by 100 micromol/L ACh was (267 +/- 106) pA (n = 11). ACh-sensitive potassium current was potently sensitive to the BK current blocker, IBTX (iberiotoxin, 200 nmol/L). Apamin, the well-known small conductance, calcium-dependent potassium current blocker, failed to inhibit the amplitude of ACh-sensitive potassium current at a dose of 1 micromol/L. ACh-sensitive BK current was sensitive to NiCl2 and potently inhibited by CdCl2. NiCl2 and CdCl2 showed a dose-dependent blocking effect with a half inhibition-maximal response of (135.5 +/- 18.5) micromol/L (n = 7) and (23.4 +/- 2.6) micromol/L (n = 7). The L-type calcium channel activator, (-) -Bay-K 8644 (10 micromol /L), mimicked the role of ACh and activated the IBTX-sensitive outward current.

CONCLUSIONACh-sensitive BK and L-type calcium channels are co-located in type II vestibular hair cells of guinea pigs.

Animals ; Calcium Channels, L-Type ; Guinea Pigs ; Hair Cells, Vestibular ; metabolism ; Large-Conductance Calcium-Activated Potassium Channels ; Patch-Clamp Techniques

OBJECTIVETo investigate the mechanism of intense noise-induced apoptosis of vestibular hair cells in guinea pigs and the effect of phosphorylated c-Jun N-terminal kinase (JNK) signal transduction pathway in intense noise-induced apoptosis of vestibular hair cells.

METHODSThirty-two guinea pigs were randomly and equally divided into 1, 5, and 15 d experimental groups and control group. The guinea pigs in the experimental groups were exposed to 4 kHz narrow-band noise at 120 dB SPL for 4 h and then subjected to measurement of auditory brainstem response at 1, 5, or 15 d after noise exposure. In each group, four guinea pigs were used to prepare paraffin sections of vestibular hair cells, and the rest for extraction of total protein from vestibular hair cells. The apoptosis of vestibular hair cells was detected by terminal deoxynucleotidyl transferase (TdT)-mediated d-UTP nick-end labeling (TUNEL). The expression levels of p-JNK and pc-Jun were measured by immunohistochemistry and Western blot.

RESULTSTUNEL-positive cells were found in the vestibular hair cells in the experimental groups, most in the 1 d experimental group and least in the 15 d experimental group, but no positive cells were found in the control group. The immunohistochemical results showed that p-JNK and pc-Jun were detected in the cell nuclei in the experimental groups, but no p-JNK- and pc-Jun-positive cells were found in the control group. The Western blot showed that p-JNK and pc-Jun were increased and activated quickly at 1d after noise exposure, reached the peak levels at 5 d after noise exposure, and were then decreased gradually, but they were still at relatively high levels at 15 d after noise exposure.

CONCLUSIONIntense noise can cause injury to vestibular hair cells by inducing cell apoptosis, and p-JNK marks the activation of JNK signal transduction pathway, suggesting that JNK signal transduction pathway plays an important role in intense noise-induced apoptosis of vestibular hair cells in guinea pigs.

Animals ; Apoptosis ; Guinea Pigs ; Hair Cells, Vestibular ; cytology ; MAP Kinase Kinase 4 ; metabolism ; Noise ; adverse effects ; Phosphorylation ; Signal Transduction