An Experimental Study Of Therapeutical Effects On Presbycusis Of Ethosuximide

ObjectiveTo investigate the protective effects of ethosuximide on presbycusis in NOD/LtJ mouse and the possible mechanisms of the protective effects.Methods① We administered ethosuximide (200 mg/kg body weight) in 3-week old NOD/LtJ mice. Auditory-evoked brainstem response (ABR) thresholds and distortion product oto-acoustic emission (DPOAE) were measured in each group at 4,6,8 weeks. ② Hair cells loss in each turns of the organs of Corti between ethosuximide-treated and untreated mice was observed using a fluorescence microscope at 8 week.③ Changes of Caspasse-3 content in hair cells of both ethosuximide-treated and untreated mice was observed by immunofluorescence staining at 8 week.④ Accumulation levels of apoptosis-related gene was measured by rt-PCR。Result1. For the two groups of NOD/LtJ mice, the ABR thresholds were measured at click stimulus frequencies at the age of 4,6 and 8 weeks, and at 8,16 and 32 kHz at 8 weeks. The ABR thresholds in the ethosuximide-treated group were significantly lower than those of the PBS group (p< 0.05) for all stimulus frequencies at 8 weeks.2. DPOAE amplitudes were measured in the two NOD/LtJ mice groups at the age of 8 weeks at f2 frequencies of 8844 Hz to 35344 Hz. The DPOAE amplitudes in the ethosuximide group at an f2 frequency of 24990 Hz were significantly higher than those of the PBS group. No significant differences were observed for the DPOAE amplitudes between the ethosuximide and PBS group at other f2 frequencies.3. OHC loss was evident in the basal turns of the cochleae of the untreated mice group at 8 weeks of age, whereas few OHC losses were seen in the corresponding areas of ethosuximide-treated mice.In the apex-middle turns, no significant difference was observed between untreated and ethosuximide-treated mice. No inner hair cell loss was observed in the ethosuximide-treated or untreated ears from the epical to basal turns.4. The gene transcription levels of apoptosis-related genes were measured in the inner ears of the ethosuximide and PBS group at 8 weeks of age. Caspase-3 was significantly upregulated (p< 0.05) in the PBS group relative to the levels measured in the ethosuximide group. At 8 weeks, the staining intensity of the caspase-3 antibodies in the hair cells was stronger in the ethosuximide group than that in the PBS group.ConclusionThis study demonstrated that ethosuximide has otoprotective effects in the NOD/LtJ mice as evaluated by a time course measurement of ABR thresholds and DPOAE amplitudes because ethosuximide blocks T-type calcium channels, which then reduces the apoptosis-related proteins.