[Alteration of the auditory function and auditory nerve pathology in Guinea pigs with peripheral nerve demyelination].
OBJECTIVE
To study the auditory function and auditory nerve pathological changes of the experimental allergic neuritis (EAN) animal model in Guinea pigs.


METHODS
To establish the animal model of EAN, heterologous myelin basic protein (MBP) of peripheral nerve was used to the immunize Guinea pigs. Serum anti-MBP-IgG levels, sciatic nerve conduction velocity (NCV), hearing thresholds and wave latencies, and pathological changes in auditory nerve, sciatic nerve and cochlea were observed. The immune lesions in inner ear were examined with immunohistochemistry. Auditory brainstem response (ABR) and compound action potential (CAP) were assayed weekly before and after immunization for a period of seven weeks. In the control group, antigen was replaced by the 0.9% saline.


RESULTS
Serum anti-MBP-IgG levels increased significantly in experimental group comparing with the control group (P < 0.01). Seiatic nerve conduction velocity decreased after immunization, as comparing with the control group (P < 0.01). Sciatic nerve and auditory nerve showed the existence of demyelination. There was significant increase of ABR and CAP thresholds and the latencies of wave I, III, V and N1 in experimental group when compared to the controls (P < 0.01), but no significant changes in inter-peak latencies of I-III, III-V were found( P > 0.05). In addition, there were 4 Guinea pigs (8 ears) in which only appeared lengthened wave latencies with normal hearing thresholds. Immunohistochemistry indicated that antibodies to inner ear from the MBP-sensitized animals distributed in cochlear nerve, neurofiber of inner ear and spiral ganglion cells. Cochlear scanning electron microscopy showed the pathology of inner hair cell with stereociliary disorder and cytoplasmic protrusions.


CONCLUSIONS
The results suggest that auditory nerve demyelination are involved in this experimental allergic neuritis animal model and sciatic nerve demyelination as well, and the auditory abnormalities are elicited. This animal model seems to be a promising one of auditory dysfunction due to demyelination disorders.
Song
Peng
P
Department of Otolaryngology, Union Hospital of Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
Gong
Shusheng
S
Luo
Linghui
L
Huang
Xiang
X
Cheng
Qing
Q
Zeng
Xiangli
X
D000200:Action Potentials; D000818:Animals; D001306:Auditory Pathways / Q000502:physiology; D003056:Cochlear Nerve / Q000473:pathology*; D003711:Demyelinating Diseases / Q000473:pathology* / Q000503:physiopathology; D004195:Disease Models, Animal; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D006168:Guinea Pigs; D008297:Male; D000159:Vestibulocochlear Nerve / Q000473:pathology* / Q000503:physiopathology