Abstract: Objective To explo reprotective effects of methioine choline on morphology and structure of hippocampal neurons in rats exposed to lead.Methods Forty SPF weanling SD rats were randomly divided in to five groups:blank,lead,methioine choline,and two lead plus different dose of methioine choline groups.After 4 and 8 weeks of treamtent,the rats were anesthetized and blood sample was collected.Atomic abso rption method was adopted to determine blood lead concen tration.Cardiac perfusion fixation was conducted and hippocampus was removed for paraffin em bedded sections.Thion in staining was adopted to observe morphology of hippocampal neurons.Transm issione lectron microscope (TEM) was used to observe ultramicro structure of hippo campus after fixation with glutaraldelyde.Results After exposed to lead for 4 and 8 weeks,the blood lead concentration of the lead exposure group increased to 274.85±19.51,294.32±11.00 ug/L.Compared with that of the lead group,the blood lead concentration of high does methioine choline group (187.25±16.02,192.68±14.17 g/L) reduced obviously with significant difference(P < 0.05).Thionin staining and TEM showed that there was no significant change in hippocampal neurons after 4 week's treatment.But after 8 weeks,some nerve cell in CA1 disappeared and necrosed and the number of the neurons reduced from 306.00±43.05 to 234.86±20.88,with ultram icrostructure changes.After giving methioine choline,the morphology and structural of hippocampal neuronal were miproved with dose-effect relationship.Conclusion The damages of hippocampal neuronal smorphology and structure caused by lead exposure is observed after longer exposure,and methionine choline palys an importantrole in the preventoin of the damages.