ABSTRACT
Objective To investigate the long-term effect of inflammation on behavior,microglias and dopaminergic (DA) neurons in the substantia nigra of intracephalic inflammation rat models induced by intracerebroventricular injection of low-dose(10μg) lipopolysaccharide (LPS).To analyze the relationship between activation of microglias and DA neurons degeneration in order to explore the mechanism of inflammation in the progressive process of Parkinson' s disease (PD).Methods 50 healthy male SD rats were randomly assigned into saline-injected control group and 10μg LPS-injected group.All injections were made intracerebroventricularly on right side of rats with saline or LPS.Moving speed was measured at different time points.At 24 weeks and 40 weeks after saline or LPS injection,specific antibodies of OX-42 and OX-6 were used separately to detect the changes of microglia in the substantia nigra of rat.The changes in morphology and numbers of substantia nigra DA neurons were observed by tyrosine hydroxylase(TH) immunohistochemical staining.The expression and distribution of the degenerated neurons in substantia nigra were detected by using Fluoro-Jade B(FJB).Results ①Analysis of moving speed sho wed that the moving speed of 10μg LPS-injected group rats and saline-injected group rats was similar from 4 weeks to 36 weeks after injection.At 40 weeks post injection,moving speed of 10μg LPS-injected group rats decreased by 24.6％ compared with that of saline-injected group rats (P＞ 0.05 ).②At 24 weeks and 40 weeks after injection,there were many activated OX-42 positive microglias in the substantia nigra of 10μg LPS-injected group rats,but there was almost no significant activated OX-42 positive microglia in saline-injected group.OX-6 positive microglias were not found in the substantia nigra of both of two groups.③At 24 weeks and 40 weeks post injection,the number of TH-positive neurons in the substantia nigra of 10μg LPS-injected group rats decreasedby 24.2％ ( t=4.803,P＜0.01) and 27.6％ ( t=3.212,P＜0.01) respectively compared with those of salineinjected group.④ There was no FJB positive neurons in the substantia nigra of the two group rats.Conclusion Intraventricular injection of low-dose LPS ( l0μg) in rats may induce long-term activation of microglias and chronic degeneration of DA neurons in the subs tantia nigra of rats although the necrosis are not occurs to DA neurons till 40 weeks post LPS injection.Intraventricular injection of low-dose LPS in rats could be ideal model to study the mechanism of chronic degeneration of DA neurons in PD.
ABSTRACT
Objective To investigate the role of asctrocytes in the process of chronic degeneration of dopaminergic neurons in intracephalic inflammation rat model induced by intracerebroventricularly injection of lipopolysaccharide.Methods Sixty healthy male SD rats were assigned into lipopolysaccharide group or saline control group randomly.All injections were made intracerebroventricularly on right side of the rats.Ethovison software was used to measure the movement distance of rats within 30 minutes.Specific antibody for glial fibrillary acid protein (GFAP) was used in immunohistochemistry stain to detect the changes of asctrocytes in the substantia nigra of rats.Results Movement distance of lipopolysaccharide-injected rats decreased by 21.2% compared with saline-injected rats at 16 weeks after injection (t=2.54,P<0.05)by 27.0% (t=3.55,P<0.01) at 24 weeks and by 31.4% (t=3.91,P<0.01) at 28 weeks after lipopolysaccharide injection.The asctrocytes were activated obviously in the substantia nigra of lipopolysaccharide-injected group at 2 weeks,while the numbers of GFAP-positively stained cells (228.60 + 22.35) increased significantly compared with saline-injected group ( 165.20 ± 25.97) (t = 4.14,P< 0.05).The activation of asctrocytes was not found in lipopolysaccharide-injected group at 4 weeks and 12 weeks.The asctrocytes were re-activated in the substantia nigra of lipopolysaccharide-injected group at 24 weeks,while the numbers of GFAP-positively stained cells (220.00±21.01 ) increased significantly compared with saline-injected group (169.00± 19.00) (t= 4.03,P<0.05).The activation of asctrocytes was not seen at any time point in saline-injected group.Conclusions Intracephalic inflammation induces chronic degeneration of substantia nigral dopaminergic neurons in rats.The asctrocytes exhibite "acute activation-quiescing-reactivation" state,indicating that they might be involved in the mechanism of dopaminergic neurons degeneration.