| The Superior Colliculus (SC) is a lamina structrue of the mammalian midbrain. It is not only the reflect center of the visul circuit,but also involved in auditory, body feeling and so on. The changes of its senile structure and function at the SC level are possibly one of the important factors which lead to the decline of visual function. This thesis makes a comparative study of the age differences between the young cats and the old cats at the level of SC.1. Nissl stain was used to exhibit the structure and neurons, and immunohistochemical method (SABC method) was applied to exhibit the S100-IR cells. Results showed that S100 protin was wide distributed in the cat SC, and S100-IR cells in the gray layers were denser than in the white layers. Compared with that of young cats, neurons density in gray layers in old ones decreased while the S100-IR cells in old ones increased in the density, swelled in the body, enhanced in the immunoreactivity. The SC astrocytes in gray layers in old animals have obvious reactive increasing, which may have positive influences to maintain the morphological structure of SC and detain the visual degeneration in senescence.2. Immunohistochemical method was introduced to exhibit the GABAergic neurons. The GABA immunoreactive cells, the fibers and their teminals were distributed widely in superficial superior colliculus (sSC) in young and old cats. The density of the GABAergic neurons declined significantly in the old cats when compared with the young adults. Result showed that the diameter, density, and number of GABAergic neurons in old cats declined significantly in comparison with the young adults (P<0.01). The inhibiting ability of GABA immunopositive neurons in the superior colliculus 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 stratum of the superior colliculus.
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