MTT reduction assay was used for the quantitative detection of the inhibitory activity of GIF in the rat hippocampal nerve call culture system. Evaluation of the influence of presence of Rab3a on the inhibitory activity of GIF indicated that Rab3a is enough to support the inhibitory activity of GIF instead of AD brain extract. Subsequently, the influence of antibody of GIF or Rab3a on the interaction between GIF and Rab3a was examined. The results indicated that Rab3a was most important to the inhibitory activity of GIF, and the interaction between GIF and Rab3a deeply depend on the spatial conditions. The mechanism and significance of the interaction between GIF and Rab3a are discussed.