Age-related Increase in Astrocytes in the Visual Area V2 of the Cat

We determined age-related changes of astrocytes in the visual area V2 of young (2–3 years old) and old (12–13 years old) cats. An immunohistochemical method was applied to demonstrate glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes. Under the microscope, the densities of the astrocytes and the diameters of the somata were calculated, and the processes of the astrocytes were also counted. Compared with the young adults, the old cats showed significantly denser astrocytes in both the cortex and medulla, accompanied with significant hypertrophy in the cell bodies, a remarkable increase in the processes, and an obvious increment in the intensity of GFAP immunoreactivity. These findings indicate a significant enhancement of astrocytic activities in the visual cortex during aging process. This enhancement might provide neuroprotective effects to the aging neurons and compensate for declining visual function in senile individuals.