猫外侧膝状体年龄相关性形态学变化

AGE-RELATED MORPHOLOGICAL CHANGES IN THE LATERAL GENICULATE NUCLEUS OF THE CAT

目的比较青年猫与老年猫外侧膝状体(lateral geniculate nucleus,LGN)神经元及γ-氨基丁酸(gama-aminobutyric acid,GABA)能神经元的年龄相关性变化,探讨老年个体视觉功能衰退的相关神经机理。方法Nissl染色示猫外侧膝状体分层结构(A、A1、C3层)及神经元,免疫组织化学法示GABA免疫阳性神经元。光镜下观察、拍照,Nissl染色切片测量外侧膝状体各层厚度、神经元胞体直径并计数神经元数量;免疫组化染色切片测量外侧膝状体各层中GABA阳性神经元胞体直径并计数GABA阳性神经元数量。结果青年猫及老年猫外侧膝状体各层厚度、神经元数量及胞体直径无明显改变(P>0.05);与青年猫相比,老年猫外侧膝状体各层中GABA阳性神经元数量及胞体直径均有不同程度的显著下降(P<0.01),且GABA免疫阳性反应减弱。结论在动物个体衰老进程中,外侧膝状体总体神经元保持相对稳定可能对老年个体维持视觉功能具有一定意义;老年个体外侧膝状体GABA能神经元对视觉信息传递及整合过程的抑制性调节功能削弱,可能是外侧膝状体水平上导致老年个体视觉功能衰退的原因之一。

Objective To comparatively investigate age-related morphological changes of total neurons and gama-aminobutyric acid （GABA） immunopositive neurons in the lateral geniculate nucleus （LGN） of young adult and old cats, and to discuss the neural mechanism of the visual degeneration in senescence underlying these changes. Methods Nissl staining was applied to show laminar organization （laminae A, A1, and C） and the total neurons of LGN; Immunohistochemical method was employed to exhibit the GABA immunopositive neurons. Under microscope, the number of the total neurons and the GABA immunopositive neurons were counted; the thickness of laminae and the diameter of the total neurons and the GABA immunopositive neurons were measured. Results The thickness of laminae, the number and the diameter of the total neurons in LGN showed no evident differences between young and old cats （P〉0.05）. Compared with that of young cats, the number and the diameter of GABA immunopositiye neurons declined significantly in the LGN of old cats （P〈0. 01）. In addition, the intensity of immunoreaction in young cats was visibly stronger than in old cats. Conclusion The relative stability of the total neurons in the LGN of old cats may be significant to maintain visual function in old individuals. However, the inhibiting ability of GABA immunopositive neurons in the LGN of old cats weakens in the course of adjusting visual information transmission and integration, which might be one of the factors effecting the visual degeneration in senescence at the LGN level.