[Observation of auditory brainstem response and distortion product otoacoustic emission on the animal model of autoimmune auditory neuropathy].

OBJECTIVE

To set up an animal model of autoimmune auditory neuropathy and to observe the auditory brainstem response (ABR) and distortion product otoacoustic emission (DPOAE) in guinea pigs.

METHODS

The spiral ganglion and the cochlear nerve were obtained and purified by electrophoresis from 250 normal guinea pigs. The purified cochlear nerve antigen was mixed with an equal volume of complete Freunds adjuvant for immunization. Seventy guinea pigs were divided into three groups: experiment group (50 guinea pigs), control group (10 guinea pigs), normal group (10 guinea pigs). ABR, DPOAE, serum IgG levels, and morphological changes of spiral ganglion cells and the cochlear nucleus were observed. The protein expressions of the antigen were examined by immunohistochemistry and the super-structure of the auditory nerve were observed.

RESULTS

The threshold of ABR response increased ranged from 10 to 25 dB in 32% (32/100 ears) of the guinea pigs. The peak latencies of waves I , III and the interpeak latency I approximately III were prolonged in the hearing loss group of guinea pigs. Prolonged peak latency of wave III was noted in hearing loss group at 2 and 3 weeks post immunization and slowly decreased to normal peak latency. The amplitude of DPOAE was no difference in the guinea pigs. The levels of serum IgG increased significantly compared with those of the control group. Inflammatory cell infiltration was observed in the cochlear nerve and the number of spiral ganglion cells detected. On the contrary, inflammatory cell infiltration was not observed in the cochlear nucleus. The cell densities and the across-sectional areas of neurons in anteroventral cochlear nucleus and posteroventral cochlear nucleus were no difference in the guinea pigs. The antigen protein distributed strictly in cochlear nerve and the spiral ganglion. Some demyelinated areas in cochlear nerve was observed in this group. The threshold of ABR response in 68% guinea pigs (68/100 ears) did not increase. The data of DPOAE and the serum IgG levels show no difference compared with the control group. There were not pathological observation in spiral ganglion cells, cochlear nucleus and cochlear nerve.

CONCLUSION

An animal model of autoimmune auditory neuropathy has been set up successfully and the character of the ABR and DPOAE was observed.