The Study On Damage Of Acoustic Nerve In Experimental Autoimmune Encephalomyelitis In Rats

Background Multiple Sclerosis(MS) is a central nervous system demyelinating disease.The mainly change of pathology was in white matter of nervous system.Brainstem Auditory Evoked Potential(BAEP) was one of the most important methods to discove the subclinical focal.And BAEP records the electric activity of auditory way from acoustic nerve to acoustic radiation.The latencies of waveâ… were emerged from the peripheral acoustic nerve.Though the lesion of peripheral nerve in MS patients was deputing,the hearing loss in MS patients were existing,especially on acute phase.The average percentages of abnormal BAEP in MS patients is almost 60%.And the percentages of abnormal latencies of waveâ… of BAEP was from 2%to 10%.The mainly changes of the BAEP are the prolong of the latencis and interpeak latency or the degrade even absence of amplitude.Experimental Autoimmune Encephalomyelitis(EAE) is a classical animal model to study the MS in the world.In this study,we establish EAE to study the change of BAEP and histologic of acoustic nerve in EAE rats.Objective To establish experimental allergic encephalomyelitis study the relationship between brainstem auditory evoked potential and histologic of acoustic nerve in EAE rats. Methods The animal,80 Wistar rats were randomly divided into control groups and experimental group pairs.Wistar rats were induced to establish EAE model by injecting guineapig with spinal cord homogenate(GPSCH) in complete Freund's adjuvant(CFA) Bacillus Calmette-Guerin Vaccine(BCG). The control groups' rats were injected Sodium Chloride with complete Freund's adjuvant(CFA).Weight and clinical scale and pathological change were observed.BAEP was assayed when EAE rats were appearing clinical symptoms. The cerebrum,spinal cord and brainstem were examined with light microscopy. And peripheral cochlear nerve was examined with transmission electron microscopy.Results The weight of rats decreased significantly in EAE group comparing with the control group after immuned.Most rats developed clinical EAE of immunization within twelve to eighteen days.In the BAEP study,the latencies of waveâ… were prolonged significantly in the both sides of the diseased rats during the acute phase.There was insignificant on clinical scale between the rats of peripheral acoustic nerve demyelinated or not.Light microscopy showed that cerebrum,spinal cord and brainstem were infiltrating lymphocytes and diffusely demyelinated.And transmission electron microscopy showed that myelin sheath of the peripheral cochlear nerve was loosing and attenuating and immaturity demyelinate but integrated axon in the EAE diseased rats.There wasn't significant change of myelin in control group's rats.Conclusions The result of histological examination indicates that demyelination not only occurs in auditory center but also occurs in peripheral acoustic nerve which may be responsible for the waveâ… of BAEP abnormalities in this EAE diseased rats during the acute phase.There may be no relationgship between the demyelination of the peripheral acoustic nerve and the clinical scale directly.And BAEP is one of the most important methods to discove the clinical focals and subclinical focal in acute EAE rats.