Abstract: Objective To study effects of excess iodine intake on synaptophysin expression in the cerebrum of filial mice and the intervention of selenium.Methods Sixty BALB/c mice were divided randomly into four group swith different drinking water:control group(tap water),excess iodine group(3 000 μg/L),supplementing selenium group(200 μg/L) and excess iodine plus selenium(3000 μg/L of iodine+I 200 L g/L of selenium)group.The mice were mated at the end of the fourth month.Serum T4 and T3 were determined on 14th and 28th postnatal day.The expression level of synaptophy sin in filial cerebrum was measured with fluore scentreal tmie PCR and Western blot.Results Serum T4 level in excessiod ine group(68.78±11.10 nmol/L)was lower significantly than that of in control group(100.85±11.47 nmol/L)and excess iodine plus selenium group(93.15±12.10 nmol/L)on 14th postnatal day.mRNA and prote in level of synap to physin in excess iodine group(relative mRNA and prote in level was 44.87±3.82 and 0.64±0.02)was lower than that in other groups(relative mRNA level was 58.34±8.13,54.33±5.32,49.89±7.46,relative protein level was 0.78±0.01,0.76?0.01,0.81±0.03,respectively)on 14 th postnatal day(P<0.05).No significant difference was observed in serum T4 and level of synap to physin between four groups on 28th postnatal day.Conclusion Excess iodine intake can change the expression of synaptophysin in cerebrum and selenium of filialmice and selenium supplementation can alleviate it.