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Objective To study the correlation between dopamine and glutamate receptor NMDA NR_1 and NMDA NR_(2A),and to share the understanding of the mechanism of dopamine in the synaptic complex of inner hair cells.Methods Forty guinea pigs were divided randomly into four groups and the whole intacochlear perfusions were performed.The perfused cochleas were taken out as preparations 2 hours after perfusing,the contralateral cochleas were also taken out as the normal control group in the group perfused with artifical perilymph solutions.All the preparations were divided into 5 groups:①normal control cochleas;②perfused with artificial perilymph solutions;③perfused with artifical perilymph solutions containing 10 mmol/L dopamine；④perfused with artificial perilymph so lutions containing 30 mmol/L dopamine；⑤perfused with artifical perilymph solutions containing 50 mmol/L dopa mine.The semi-quantitive RT-PCR was used to observe the difference in the amount of glutamate receptor NMDA NR_1、NMDA NR_(2A).Results Dopamine inhibited the compound action potential(CAP),the increase of CAP threshold was observed and correlated with the contentration of dopamine in the perfusion solution.Regarding the amount of glutamate receptor NMDA NR_1 mRNA,there was no significant difference between group ① and group ② (P＞0.05).But a significant difference was observed the other 3 groups when compared to group ①(P＜0.05).No significant difference was detected among the 5 groups in the amount of glutamate receptor NMDA NR_(2A) (P＞0.05).Conclusion Dopamine may inhibit the cochlear auditory afferent nerve.The significant correlation between dopamine and glutamate receptor NMDA NR_1 was observed,the amount of glutamate receptor NMDA NR_1 decreased along with the increasing of the contentration of dopamine in the perfusion solution.And there was no significant correlation between dopamine and glutamate receptor NMDA NR_(2A).
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Objective To observe the action of H_2O_2 on the hair cells in the organ of Corti of rats.Methods The culture technology of Corti in neonatal rat in vitro was used to establish the model of studying the injury of inner and outer hair cells caused by exogenous H_2O_2. 24 neonatal SD rats of 1～ 5 days were selected and divided into 4 groups with 6 in each group.There were 12 ears in each group:①serum-free medium;②0.05 mmol/L H_2O_2;③0.1 mmol/L H_2O_2;④0.5 mmol/L H_2O_2.Forty-eight hours after the tissues cultivation, the tissue was stained by AO and PI.The ratio of apoptotic cells in different groups was studied.Results Apoptosis cells were detected in groups of different concentration of H_2O_2.Outer hair cell were the main target attacked by H_2O_2.But not at apoptotic Sertoli cells.The loss of hair cells on the bottom,middle and parietal turn of basilar membranes varied as the injury to the bottom turn was more severe.The results suggest OFR could cause apoptosis of hair cells,and cochlea damage was dose-dependent in this way.Conclusion Under the conditions of this experiment,exogenous H_2O_2 can cause the apoptosis of hair cells of the organ of Corti in rats,but not related to apoptotic Sertoli cells.
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Objective To investigate plasma pharmacokinetics profiles of compound betameth in guinea pig after postaurieal and systemic administrations,and to explore the possible pathway for postaurical injection. Methods 1 ml compound-betameth was injected postaurieally and intramuscularly into the guinea pig. Blood were samples obtained 0. 5,1,1.5,2,3,5,7 h and 1,2,4 w after the administration of contralateral sigmoid sinus blood and circulatory blood respectively. High performance liquid chromatography was used to dectet compound betameth in the samlowing postaurieal administration. The Cmax(peak concentration) in sigmoid sinus of postaurieal group was 2.56 and 3.03 higher than those in the contralateral and the systemic group. The AUC((area under the ct curve) was 2.41 postaurieal administration. The Cmax and AUC in postaurieal group were 0. 13 and 0. 32 higher than systemic group. Conclusion The postaurieal injection reached a higher concentration of drugs in the sigmoid sinus blood, and remained a lower concentration in circulatory blood.
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OBJECTIVE To investigate the protective effect and its frequency selection of dopamine on the inner cell in cochlea when exposed to white-noise;In order to offer an important step on understanding of negative protective modulation of dopamine in the cochlear auditory afferent nerve. METHODS Forty guinea pigs were randomly divided into 4 groups and whole intracochlear perfusions were performed. ① exposed to the 100dB white-noise; ② perfused with artificial perilymph solutions; ③exposed to the white-noise and perfused with artificial perilymph solutions; ④exposed to the white-noise and perfused with Artificial perilymph solutions containing 1mmol/L dopamine. Compound action potential(CAP)evoked by different frequencies tone pip, and cochlear mirophonics(CM)evoked by 4kHz tone burst were recorded from the round window of guinea pigs before and 2h after perfusion. RESULTS In the groups exposed to the white-noise, the CM amplitude and the linearity of input-output function both significantly decreased at 2h(P
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OBJECTIVE To analyze 1000 Hz probe tone tympanometry of middle ear with different volume of fluid, and to evaluate the role of 1000 Hz probe tone tympanometry in the diagnosis of presence of fluid in tympanic cavity. METHODS Tympanometries with 1000 Hz or 226 Hz probe tone were obtained from all the guinea pigs with different volume of fluid in tympanic cavity using GSI33 analyzer and tympanometry curves were analyzed. RESULTS There was a significant difference of the peak pressure of 1000 Hz tympanometry among all test groups and control group. The peak pressure decreased with the increasing of fluid volume in tympanic cavity. CONCLUSION Tympanometry with 1000 Hz probe tone can be used in the diagnosis of fluid in tympanic cavity, and it can be an indicator of volume of fluid in tympanic cavity.
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0.05). A rise in CAP threshold and reduction in CM amplitude after perfusion were found in the other three groups(P
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<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>
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Animals , Action Potentials , Calcium , Physiology , Cochlea , Pathology , Physiology , Endolymph , Metabolism , Guinea Pigs , Hair Cells, Auditory , Metabolism , Hearing Loss, Noise-Induced , Perilymph , PhysiologyABSTRACT
<p><b>OBJECTIVE</b>To investigate the effect of D-AP5 (D-2-amino-5-phosphonopentanoate, a specific NMDA-antagonist) on the increase of intracellular free Ca2+ concentration ([Ca2+]i) induced by glutamate in isolated cochlear inner hair cells (IHCs), and to detect the autoreceptors of the IHC membrane.</p><p><b>METHODS</b>When a laser scanning confocal microscope (LSCM) was used, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs and OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca2+]i. After D-AP5 or CNQX (6--cyano--7--nitroguinoxaline--2, 3--dione, a specific AMPA- antagonist) was administered, the exogenous glutamate (Glu)-induced changes in [Ca2+]i of isolated IHCs were recorded.</p><p><b>RESULTS</b>In the presence of a low concentration Glu (3.85 mumol/L), there was an increase of [Ca2+]i in IHCs, whereas there was no change in OHCs. When 50 mumol/L of D-AP5 was administrated in advance, Glu did not induce a corresponding increase in [Ca2+]i in IHCs, and 50 mumol/L of CNQX did not completely block the increase of [Ca2+]i in IHCs.</p><p><b>CONCLUSIONS</b>These results suggest that the autoreceptors existing in the IHC membrane are mainly of NMDA type, while there are relatively few AMPA receptors. Exogenous Glu is capable of increasing [Ca2+]i in IHCs by acting on the NMDA autoreceptor of IHCs in a positive feedback manner.</p>
Subject(s)
Animals , 2-Amino-5-phosphonovalerate , Pharmacology , 6-Cyano-7-nitroquinoxaline-2,3-dione , Pharmacology , Calcium , Metabolism , Excitatory Amino Acid Antagonists , Pharmacology , Glutamic Acid , Pharmacology , Guinea Pigs , Hair Cells, Auditory, Inner , Metabolism , In Vitro Techniques , Receptors, N-Methyl-D-AspartateABSTRACT
Objective To establish reliable tissue culture methods of organ of Corti in neonatal Wistar Rat.Methods The organ of corti was aquired from Wistar Rat with the method of microdissection.The tissues were cultured by two different methods.Results Twenty-four hours after the tissue cultivation,new epithelia cells and fibroblast were found around the tissue.Inner hair cell、outer hair cell and supporting cell grew well.The tissue was stained by Acridine orange and Prodium iodine.It became green,meaning the tissue had good activity.Conclusion The culture of organ of corti we introduced is an a ideal method for otology research.
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Objective To investigate the effects of hydrogen peroxide on function and morphology of guinea pig cochlea in vivo.Methods Animals were divided into four groups and their cochleas were perfused with artificial perilymph(AP), 50 ?M H 2O 2, 100 ?M H 2O 2 and 200 ?M H 2O 2 resolved in AP separately. The compound action potential(AP) and cochlear microphonic(CM) were recorded after two-hours' perfusion. Then hydrogen peroxide-induced cell damage in the inner ear was investigated with morphologic method.Results In all H 2O 2 groups, CAP threshold shifts and CM amplitude shifts were significantly greater than that of APL group. The effect of H 2O 2 perfusion on cochlear function showed dose-dependence. OHCs were major targets of H 2O 2-induced cell death, while Hensen's cells did not show any signs of damage in the presence of H 2O 2. Conclusion Hydrogen peroxide, as an ubiquitous reactive oxygen species(ROS), can induce cochlea dysfunction and damage of cells in guinea pig inner ear. Hensen's cells maybe more resistant to the damage of ROS than hair cells.
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The purpose of this study was to assess the diagnostic value of main frequency of transient evoked otoacoustic emissions for Meniere's disease. The click- evoked transient otoacoustic emissions(TEOAE) in normal subjects and in patients with Meniere' s disease were examined using ILO 88 otodynamic analyzer system to observe the main frequency distrbution. The main frequeencies ranged from 1.2 to 1.6 kHz in normal ears, and from 0.8 to 1. 1 kHz in Meniere' s ears. The main frequency range of normal ears was obviously higher than that in Meniere's ears. After application of glycerol, the main frequencies in some Meniere's ears were shifted from relative low frequency range to relative high frequency range. TEOAE appeared in some Meniere's ears in which TEOAEs could not be evoked before application of glycerol. The results suggest that the TEOAE can be used in the diagnosis of Meniere's disease.