猫下丘中央核5-HT、P物质和星形胶质细胞年龄相关变化

Age-related changes of 5-HT,substance P,and astrocytes in inferior colliculus center of cats

目的比较研究青年猫与老年猫下丘中央核(CIC)5-羟色氨(5-HT)、P物质(SP)能神经元及星形胶质细胞年龄性变化,探索老年个体听力下降的神经机制。方法 Nissl染色显示下丘神经元,免疫组织化学ABC法显示5-HT、SP和胶质纤维酸性蛋白(GFAP)免疫反应(immunoreactive,IR)细胞。光镜下观察、拍照,对神经元和5-HT、SP及GFAP免疫反应细胞分别计数并换算成密度,测量其IR细胞直径取平均值,以及它们的阳性反应平均灰度值。结果 5-HT-IR、SP-IR和GFAP-IR细胞、阳性纤维及其终末在青年猫及老年猫下丘中央核均有分布。与青年猫相比,老年猫下丘中央核5-HT密度均显著下降(P<0.01),胞体直径明显减小(P<0.01),阳性反应明显减弱(阳性反应强度与灰度值呈负相关),SP-IR神经元和星形胶质细胞密度却显著增大,阳性反应显著增强。结论在衰老过程中猫下丘神经元尤其是5-HT能神经元有显著丢失现象,提示5-HT能神经元显著减少导致下丘听觉信息传递功能减弱,可能引起老年个体听觉功能衰退的重要原因;SP能神经元和星形胶质细胞密度显著增大,可能起到延缓衰老的作用。

Objective Age-related changes of 5-HT,SP,and astrocytes in the inferior colliculus of young adult and old cats were investigated comparatively,and the neural mechanism of the auditory degeneration during senescence underlying these changes was discussed.Methods Nissl staining was used to display all the inferior colliculus neurons,and immunohistochemical method was used to exhibit 5-HT immunoreactive（5-HT-IR） cells,substance P immunoreactive（SP-IR） cells,and astrocytes.Under the microscope,the number of the 5-HT-IR cells,SP-IR cells and astrocytes was counted,and their diameter and density were measured.Results The 5-HT-IR cells,SP-IR cells,astrocytes,fibers and their teminals were distributed widely in central neucli of inferior colliculus in young and old cats.The diameter and density of 5-HT-IR ergic neurons declined,while grey value significantly increased in the old cats when compared with those of the young adults.But SP-IR cells and astrocytes were on the contrary.Conclusion An evident loss of the 5-HT-IR neurons in old inferior colliculus may result in an imbalance of excitement and inhibition,which might be an important reason for the auditory degeneration in senescence.The functional increase of SP and astrocytes may delay aging.