Objective      To study the change of myelinated fibers in corpus callosum of immature rats after status convulsion (SC) induced by lithium-pilocarpine.       Methods      Seventy-four immature SD rats

in which SC was induced by lithium chloride-pilocarpine (pilo group) and forty-eight immature SD rats (control group) were evaluated. Morphological changes of myelinated fibers in corpus callosum were examined by Gallyas staining. The expression of myelin basic protein (MBP) was determined by Western blotting. The micro-structural characteristics of myelinated fibers were determined by transmission electron microscopy at different time points (acute phase

latency phase

beginning of chronic phase and chronic phase).       Results      It was found that the callosal myelinated fibers of the pilo group were degenerated

and the MBP expression in corpus callosum of the pilo group was significantly decreased in comparison with the control group at the acute phase lasting to the chronic phase after SC. While the myelinated nerve fibers in control rats were normal

with plasma membrane rings of regular heights and dense structure

the fibers in pilo-treated rats showed stratification

collapse and disruption

as well as disordered arrangement at different time points after SC.       Conclusion      Myelinated fiber damage in corpus callosum of immature rats is irreversible at acute phase after SC.