Age-related structural changes in feline cerebellar cortex

Objective: To compare the age-related changes of cerebellar cortex of young and old cats. Method: Nissl staining was applied to exhibit cortical neurons; immunohistochemical method was used to display GFAP-immunoreactive (GFAP-IR) astro-cytes and neurofilament-immunoreactive (NF-IR) neurons. The thickness of cerebellar cortex was measured and the density of neurons in all layers as well as the dennsity of GFAP-IR cells in granual layer were analyzed under microscope. Results: Compared with young adult cats, the old cats presented a significantly decreased thickness of the molecular layer and the total cerebellar cortex and an increased thickness of the granular layer. The density of neruons in each layer was significantly lower in old cats than that in young adults. Astrocytes in old cats were significantly denser than that in young adult ones, with evident hypertophy of cell bodies and enhanced immunoreaction of GFAP substance. PCs in old cats showed much less NF-IR dendrites than that in young adults. Conclusion: The above results indicate an evident neuron loss and decreased PC's dendrites in the old cerebellar cortex, which might underlie the functional decline of afferent efficacy and information integration in senescent cerebellum. An age-dependent activity enhancement of astrocytes may exert protective effect on neurons in the aged cerebellum.