猫上丘浅层GABA能神经元的年龄相关性变化

AGE-RELATED CHANGES OF GABA IMMUNOREACTIVE NEURONS IN THE SUPERFICIAL SUPERIOR COLLICULUS OF CATS

目的比较青年猫和老年猫上丘浅层(superricial Superior Colliculus,sSC)GABA能神经元及其表达的年龄相关性变化,探讨老年个体视觉功能衰退的相关神经机理。方法Nissl染色显示上丘浅层结构及神经元、免疫组织化学ABC法标记GABA免疫阳性神经元。光镜下观察,采集图像,并利用图像分析软件对带状层、浅灰质层和视层神经元及GABA免疫阳性神经元及其灰度值进行分析统计。结果GABA免疫阳性神经元、阳性纤维及其终末在青年猫及老年猫上丘浅层均有分布。与青年猫相比,老年猫上丘浅灰质层、视层神经元和GABA免疫阳性神经元密度及其GABA免疫阳性反应强度均显著下降(P<0.01)(免疫反应强度与平均灰度值成反比);带状层神经元密度也显著下降(P<0.01),但其GABA免疫阳性神经元密度无显著变化(P>0.05)。结论衰老过程中猫上丘浅层GABA能神经元的丢失和GABA表达的下降,可能是在上丘水平上导致老年个体视觉功能衰退的重要因素之一。

Objective To comparatively investigate age-related changes of GABAergic neurons and GABA expression in the superficial superior colliculus of young adult and old cats, and to discuss the neural mechanism of the visual degeneration in senescence underlying these changes. Methods we applied Nissl staining to show the structure and neurons in the superricial superior colliculus. Immunohistochemical method was used to show the GABA immunoreative neurons. Under light microscope , the numbers of total neurons and GABAergic neurons in the stratum zonal, stratum griseum superficia and stratum opticum were counted respectively, and the average gray value of GABA immunoreactive neurons was analysed with the Image-pro Express Software. Results The GABA immunoreactive cells, the fibers and their terminals were distributed in each layer of superficial superior colliculus. Compared to that of young cats, the number of the neurons and GABA immunoreactive neurons declined significantly in the stratum griseum superficia and stratum opticum （P〈0. 01） . However, no difference was observed in the number of GABA immunoreactive neurons in the stratum zonal of young and old cats （P〉0.05） . Conclusion An evident loss of GABAergic neurons and decline of GABA expression during aging might be one of the important factors resulting in the visual functional degeneration at the superior colliculus level.