Abstract: Objective:To investigate the expressions of phosphorylated extracellular signal-regulated kinase (pERK) in the hippocampus of the mice of embryonic(E)18 d and postnatal(P)1,3,7,14,21 and 28 d,and to discuss its possible role during the hippocampus development of the mice. Methods:The hippocampus tissues of the mice of E 18 d,P 1 d,P 3 d,P 7 d,P 14 d,P 21 d and P 28 d were obtained.Each time point was used as observation group. Immunohistochemistry,Western blotting and image analysis technique were used to analyze the expression levels of pERK protein in hippocampus tissue at each time point. Results:The immunohistochemistry results revealed that pERK protein mainly expressed in the nucleus of the nerve cells in the granular layer of dentate gyrus and pyramidal layer of Ammon's horn in hippocampus. In the mice of E 18 d, the expression of pERK in DG and CA regions of hippocampus were slightly stained and arranged sparsely, and the expression level was low;and the pERK was deeply stained and the expression levels of pERK were increased gradually with the development of the hippocampus from E 18d to P 7 d;compared with other six time points, the expression level of pERK of the mice of P 7 d was the highest(F=34.537, P<0.01).From P 14 d to P 21 d,the pERK was slightly stained and the density was decreased;the expression levels of pERK were decreased (F=28.754,P<0.01),and then remained stably on P 28 d(F=6.075, P>0.05). The Western blotting results showed that pERK expressed at each time point,from E18 d to P7 d,the expression levels of pERK were increased gradually; compared with other six time points,the expression level of pERK on P 7 d was the highest (F=33.856, P<0.01).The expression levels of pERK were decreased from P 14 d to P 21 d(F=22.627,P<0.01),and then remained stably on P 28 d(F=7.421,P>0.05). Conclusion:The hippocampus development is increased significantly at the early stage of the mice(E18-P 7d),and the expression levels of pERK are increased gradually in the meanwhile;the expression level peaks on P 7 d, and then it is gradually decreased until a stable level. pERK may take part in the cell proliferation in the development of hippocampus of the mice.

Key words: extracellular signal-regulated kinase, hippocampus development,Kuming,mice, immunohistochemistry, immunoblotting method