Long-term effects of anterograde degeneration on astroglial reaction in the rat geniculo-cortical system as revealed by computerized image analysis.

Changes in the expression of glial fibrillary acidic protein by astrocytes in the primary visual cortex of adult albino rats were analyzed with immunohistochemistry after unilateral destruction of the dorsal lateral geniculate nucleus. An increase in number of glial fibrillary acidic protein-immunoreactive astrocytes could be detected in the visual cortex of the side ipsilateral to the lesion in the short-term survival group (7-11 days post lesion), but this increase was extremely reduced after a postlesional survival time of 150 days. The quantitation of the glial response by image analysis showed, that the initial increase was mainly localized in the cortical layers II-IV, where the geniculo-cortical input terminates. The transient nature of this process was revealed by the measurements in the long-term survival group, where differences between experimental and control sides were substantially reduced. We conclude, that the remote glial response in the visual cortex is transient and that is disappearance indicates the end of a postlesional adaptation period in the neuropil.