低剂量脂多糖脑室注射对大鼠行为黑质小胶质细胞及多巴胺能神经元的长时程影响

Long-term effect of intraventricular injection of low-dose lipopolysaccharide on behavior, microglias and dopaminergic neurons in the substantia nigra of rats

目的利用大鼠脑室内注射低剂量脂多糖（1ipopolysaccharide，LPS）（10Ixg）诱导全脑炎症，长时间观察大鼠行为学、黑质部位小胶质细胞激活及多巴胺（Dopamine，DA）能神经元的变化，研究小胶质细胞激活与DA能神经元损害的关系，探讨炎症在帕金森病（Parkinson’s disease，PD）发病机制中的作用。方法50只雄性sD大鼠分为生理盐水对照组和10μgLPS组。大鼠右侧脑室内注射生理盐水或10μgLPS，术后不同时间观察大鼠行为学改变，免疫组化方法观察大鼠黑质部位小胶质细胞激活情况及酪氨酸羟化酶（tyrosinehydroxylase，TH）阳性神经元的变化。Fluoro—JadeB（FJB）染色检测大鼠黑质部位神经元变性情况。结果①注射后4周至36周两组大鼠平均运动速度相近。注射后40周时10μgLPS组大鼠平均运动速度比生理盐水对照组降低24．6％（P〉0．05）。②注射后24周和40周，10μgLPS组大鼠黑质部位可见明显激活的0X-42阳性小胶质细胞，生理盐水对照组未见明显激活的0X-42阳性小胶质细胞。两组大鼠黑质部位均未发现OX-6阳性小胶质细胞。③注射后24周和40周，10p．gLPS组大鼠黑质部位TH阳性神经元数目比生理盐水对照组分别减少了24．2％（t=4．803，P〈0．01）和27．6％（t=3．212，P〈0．01）。④两组大鼠黑质部均未见FJB阳性染色神经元。结论低剂量LPS脑室内注射可造成大鼠黑质部位小胶质细胞长期慢性激活及DA能神经元慢性损害。LPS诱导的全脑炎症在短时间内不会引起黑质DA能神经元变性坏死。脑室内注射10μgLPS模型能很好模拟DA能神经元慢性变性的特点，是研究PD的较好模型。

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 activa- tion of microglias and DA neurons degeneration in order to explore the mechanism of inflammation in the progres- sive process of Parkinson＇s disease （PD）. Methods 50 healthy male SD rats were randomly assigned into sa- line-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 （1）Analysis of moving speed showed 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 ）. （2）At 24 weeks and 40 weeks after injection,there were many activated 0X-42 positive microglias in the substantia nigra of 10μg LPS-in- jected 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. （1）At 24 weeks and 40 weeks post injection, the number of TH-positive neurons in the substantia nigra of 10μg LPS-iniected rout3 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 suhstantia nigra of the two group rats. Conclusion Intraventricular injection of low-dose LPS （10μg） in rats may induce long-term activation of microglias and chronic degeneration of DA neurons in the substantia nigra of rats although the necrosis are not occurs to DA neurons till 40 weeks post LPS injection. Intravenlricular injection of low-dose LPS in rats could he ideal model to study the mechanism of chronic degeneration of DA neurons in PD.