Objective:To investigate the effect of early malnutrition on the activation of microglia in the hippocampus of adult rats.Methods:Early malnutrition model was established in SD rat

and all rats were given supplement of n-3-polyunsaturated fatty acid（n3-PUFA）after lactation. Weight of newborn rats was measured. The ability of learning and memory of offspring rats were assayed by Morris water maze and the fear conditioning. Real-time quantitative PCR and Western blot were used to assay the expression of microglia M1 markers such as inducible nitric oxide synthase（i NOS）

cyclooxygenase-2（COX-2）in the hippocampus. The expressions of microglia marker Ionized calcium binding adapter molecule-1（IBA-1）in the hippocampus were detected by immunohistochemistry. Results:The early malnutrition group was born with lower birth weight（P=0.000）. After postnatal 90 days

the ability of learning and memory was reduced;the expression of i NOS was increased both in m RNA（P =0.002） and protein（P =0.015）;the expression of IBA-1 was increased（P=0.047）. Supplementation of n3-PUFA could reduce M1 type conversion and the activation of microglia. Conclusion:Early malnutrition may lead to up-regulation of activation of microglia and increasing of M1 phenotypic transformation in adult offspring

which may be related to the occurrence of neuroinflammation in hippocampus of adulthood.