Establishment Of An Animal Model Of IHCS Damage And Its Study Of Electrophysiology Of Audition

Objective:To investigate the test methods and characteristic of guinea pig's frequency-specific summating potential-Compound action potential and acoustic auditory brainstem responseMethod:20 healthy guinea pigs were divided into 2 groups (A and B) of 10 each. Bullae of A group were opened by, and recording electrode placed on round window. The recording electrode of B team was on cranial vault. The stimulus auditory frequency was 0.25,0.5,1, 2,4,8KHz tone pip.Results:The frequency-specific SP-CAP and AABR were recording. SP wave gradually changed from negative wave to positive wave with the frequency increasing. When stimulus duration of tone pip was longer, its frequecy-spcific was better, but the waveform of frequency-specific AABR was worse. Otherwise, the stimulus duration was shorter, its frequency-specificity was worse, but the waveform of AABR was better. Conclusion:The frequency-specific stimulus sound can induce SP-CAP complex wave; and in order to inducing a high frequency-specific AABR waves with good waveform, a reasonable parameters of stimulate sound need to set. Objective:To investigate glutamate excitotoxicity on cochlear;Methods:Guinea pigs were divided into 2 groups, the experimental group (20mmol/1 glutamate infusion group=10), the control group (artificial perilymph perfusion= 10). The whole cochlear perfusion method was used. Before and 2 hours after reperfusion SP-CAP, AABR, CM and EABR were detected. Morphology changes of the inner and outer hair cell were observed after perfusion in 5 guinea pigs each group and the left animals were detected apoptosis inducing factor on spiral ganglion 8 hours later after perfusion.Results:2 hours later after reperfusion glutamate, the threshold of CAP, A ABR and EABR increased; SP wave turn to positive from negative wave; CM amplitude got smaller, but non-linear change still existed. Inner hair cell synapses were destructed, and there were vacuolar in inner hair cells. outer hair cell morphology didn't change. There were vacuolar changes in Spiral neurons. AIF entered into the nucleus from the cytoplasm of spiral neurons.Conclusion:Glutamate have apparent toxic effects in cochlear inner hair cells and spiral neurons, and can induce apoptosis of spiral neurons by AIF.Objective:To observe the effect of DNQX on cochlear electrophysiology and morphology; Methods:DNQX was perfused for 2 hours by the method of the whole cochlear perfusion. SP-CAP, AABR, CM and EABR were testing before and after the perfusion. Morphology changes of the inner and outer hair cell were observed after perfusion in 5 guinea pigs and the left animals were detected apoptosis inducing factor on spiral ganglion 8 hours later after perfusion.Results:CAP, AABR thresholds were significantly increased, EABR, SP and CM no significant change. Inner and outer hair cells and spiral neurons had no significant morphological changes, the expression of AIF were unchanged.Conclusion:DNQX antagonized the physiological role of glutamate, but had no significant toxicity on cochlear function.Objective:To evaluate the modeling method of animal model of inner hair cell damage;Methods:20mmol/1 glutamate and 1.98mmol/lDNQX were perfuse for 2 hours by the method of the whole cochlear perfusion, SP-CAP, ABR, CM and EABR were testing before and after perfusion. Morphology changes of the inner and outer hair cell were observed after perfusion in 5 guinea pigs and the left animals were detected apoptosis inducing factor on spiral ganglion 8 hours later after perfusion.Results:The thresholds of CAP and ABR were significantly increased, but the thresholds of EABR was not; SP wave turned to positive wave from negative wave; CM had no significant changes in amplitude. Inner hair cell showed degeneration and edema. Outer hair cells and spiral ganglion had no change, and AIF were unchanged. Conclusion:The mixture perfusion of glutamate and DNQX can establish animal models with injury inner hair cells.