OBJECTIVETo study the pathological changes in the non-myelin sheath by observing histological damages to the neurofilament protein and apoptosis of neurons in rats with experimental autoimmune encephalomyelitis (EAE).

METHODSForty-eight Wistar rats were randomly divided into two groups: control and EAE (24 rats in each group). Behavioral changes were observed. Inflammation reactions and demyelination were observed by hematoxylin eosin staining and LOYEZ staining.The level of neurofilament was detected by immunohistochemistry. Apoptosis of the neuron in the spinal cord was detected by TUNEL.

RESULTSBehavioral and histological results confirmed that the model of EAE rats was prepared successfully. In the EAE group, typical morphological features of axonal damage (sparsed axonal density, axonal distortion, axonal transection and even axonal disappearance) were found from the seventh day after immunization and the morphological changes were the most obvious on the fourteenth day. Neurofilament density in the EAE group was significantly lower than in the control group (P<0.01) at 7, 14 and 21 days after immunization. The neuronal apoptosis index in the EAE group at 7, 14 and 21 days after immunization was significantly higher than in the control group (P<0.01).

CONCLUSIONSIn addition to inflammatory demyelination, axonal damage and neuronal apoptosis can be observed in the early stage of EAE. Pathological changes may be associated with neurological dysfunction.