Abstract: Objective To investigate the change of astrocytes in the hippocampus in intracephalic inflammation rat model induced by intra-ventricular injection of lipopolysaccharide(LPS). Methods Altogether 64 healthy male SD rats were assigned into normal saline(NS)-injected group or LPS-injected group randomly. All injections were made intra-ventricularly on right side of the rats with NS 20 μL or LPS 20 μL(1.25 g/L). The changes of the the astrocytes in rat hippocampus were observed by immunohistochemical staining using astrocyte-specific marker-glial fibrillary acidic protein(GFAP) at 2 weeks, 4 weeks, 12 weeks and 24 weeks after NS or LPS injection. Western blot was performed to detect GFAP expression in the hippocampus of the rats. Results Immunohistochemical staining with GFAP antibody showed that the astrocytes in the hippocampus of rats were not activated at any time point after NS injection in NS-injected group. The astrocytes were activated obviously in the hippocampus of rats in LPS-injected group at 2 weeks after LPS injection. The activation of astrocytes was not found in the hippocampus in LPS-injected group at 4 and 12 weeks while the astrocytes were re-activated slightly in the hippocampus of LPS-injected group rats at 24 weeks after LPS injection. The result of Western blotting showed that the expression of GFAP in the hippocampus of NS-injected group rats did not change significantly at any time point after NS injection. The GFAP protein level in the hippocampus of LPS-injected group rats was 239% of that of NS-injected group rats at 2 weeks after injection(P<0.01). At 4 and 12 weeks after injection, the GFAP protein level in LPS-injected group was similar to that of NS-injected group. The expression of GFAP protein in the hippocampus of LPS-injected group was 119% of that of NS-injected group at 24 weeks post injection with no significant difference(P>0.05). Conclusion Intra-ventricular injection of LPS may result in acute and significant activation of astrocytes in the hippocampus of rats at early time(2 weeks post injection).

Key words: inflammation, dopaminergic neurons, hippocampus, astrocyte