Objective To investigate the expression of calcium/calmodulin-dependent protein kinaseⅡ(CaMKⅡ) in the Wistar rat hippocampus during postnatal development. BR>Methods Immunofluorescent staining was applied to observe the expression of CaMKⅡ in the CA1, CA3 and dentate gyrus (DG) of the rat hippocampus during postnatal development (EM>n/EM> =48).Results In CA1 and DG, CaMKⅡ expression increased with age, reached a plateau at postnatal day 10 (P10) and then declined gradually. In CA3, CaMKⅡ expression reached a plateau at P4 and P10. The expression of CaMKⅡ in CA3 was higher than that in CA1 and DG. CaMKⅡ expression in the stratum polymorphum and stratum moleculare was much higher than that in the stratum pyramidale or granular cell layer.Conclusion The expression of CaMKⅡ has a specific temporal-spatial distribution pattern. The specific temporalspatial distribution pattern may be important to the different physiolo