ACOUSTIC INJURY OF GUINEA PIGS CAUSED BY ~60Co?-RAY / 第二军医大学学报

ABSTRACT

The head of guinea pig was irradiated with 60Co?-ray and a single dose of irradiation was 90 Gy and 70 Gy in two groups, respectively.Two h after irradiation, the threshold shifts were 12.5 dB and 9 dB, and the auditory cortical evoked response (ACER) maximum post-irradiation amplitude exceeded the maximum prc-irradiation value by 20% and 37%.Six h later, the threshold shift increased to 37 dB and the maximum amplitude decreased to the level of pre-irradiation in the 70 Gy group.Right auditory bulla area was irradiated with a total dose of 45 Gy in a course of six fractions in two weeks.Fourteen d after irradiation, the threshold shift of auditory brainstem evoked response(ABR)was 11.8 dB.Hjstolo-gical observation using scanning electron microscope showed that only outer hair cells in the basal coil of the cochlea were destroyed 6 h after irradliation in the 90 Gy group.But outer hair cells in all coils of the cochlea were found to be destroyed 16 h after irradiation.In the 45 Gy group, 14 d after irradiation, outer hair cells in all coils of the cochlea were damaged and no inner hair cells were injured severely.