Effect of Isoflurane on the Hearing in Mice

BACKGROUND AND OBJECTIVES: The aim of this study was to investigate the relationship between inhalation anesthetics and hearing in mice. MATERIALS AND METHODS: As inhalation anesthetics, isoflurane was used. Auditory brainstem response and distortion product otoacoustic emission were used as measurement of hearing. Mice were divided into 2 groups. 'Isoflurane group' consisted of mice that were anesthetized with an inspired concentration of 2.0 vol% isoflurane with 2 L/min of oxygen (n=10). 'Control group' consisted of mice that were anesthetized with ketamine and xylazine (n=10). RESULTS: Auditory brainstem response thresholds in mice anesthetized with ketamine and xylazine was not different from those in mice anesthetized with isoflurane. Threshold of DPOAE was higher in mice with isolurane than with ketamine and xylazine. Changes of efferent control may be induced by isoflurane and consequently change the threshold of DPOAE in mice. CONCLUSIONS: These results infer that, there was a change of central nervous system induced by inhalation anesthetics, this change also can be applied to the strategies for prevention of hearing loss.

Proteomic Analysis of the Protein Expression in the Cochlea of Noise-Exposed Mice

BACKGROUND AND OBJECTIVES: When noise-induced hearing loss occurs, destruction of the hair cells is accompanied by mechanical injury, chemical injury, and hypoxia. Proteomics is a powerful tool for protein analysis, as it provides valuable information regarding the biochemical processes involved in diseases, monitors cellular processes, and characterizes protein expression levels. We attempted to identify the proteins associated with the pathophysiology of noise-induced hearing loss, as well as the mechanisms of this disease, using a proteomics approach. MATERIALS AND METHODS: We used BALB/C male mice. The control mice were placed in a booth without noise, while the experimental mice were exposed to noise for three hours daily for three consecutive days. Cochleae from each group were obtained for total protein extraction. The proteins were separated into numerous spots using two-dimensional electrophoresis. Seven protein spots that were strongly detected only in the noise-exposed cochleae were selected and subsequently analyzed using matrix-assisted laser desorption/ionization time of flight mass spectrometry. RESULTS: Approximately 286 protein spots were detected in the noise group. Seven selected spots were analyzed and various proteins identified, including tyrosine protein kinase MEG2, angiopoietin-like 1, heat shock 70 kDa protein, sodium dicarboxylate cotransporter 1, myeloid Elf-1-like factor, disintegrin, metalloproteinase domain 7, and activated leukocyte-cell adhesion molecule. CONCLUSIONS: We identified several proteins expressed in noise-induced hearing loss using a proteomics approach. These proteins may help us to understand the pathogenic mechanisms of noise-induced hearing loss.