The Time Course of Astrocyte Proliferation Following Middle Cerebral Artery Occlusion in Primary and Secondary Regions to Infarct in Aged Rats
The left middle cerebral artery was occluded at the level of the rhinal fissure (LMCAO) via microcautry on the brains of 12 Long-Evan Blackhood Rats (10-12 months in age). One female and two male experimental rats were sacrificed 1, 3, 7, and 14 days after surgery. Then 30 µm sections were then processed for indirect immunofluoresence microscopy of astrocytes expressing glial fibrillary acidic protein (GFAP). The cerebral cortex at the infarct site, thalamus and basilar pons showed a progressive increase in the density of GFAP positive astrocytes over the survival periods. In sum, the cerebral cortex (at the lesion site) peaked in astrocytes 3 and 7 days after surgery while both the thalamus and basilar pons peaked at 14 days after (LMCAO). However, the basilar pons had a higher density of astrocytes than the thalamus. Furthermore, cortical astrocytes showed a distinct morphology different from astrocytes in the thalamus and basilar pons. Additionally, a macroscopic examination of the brains was performed in order to investigate the predictability of the infarct size produced by the microcautry technique. Two out of twelve animals sustained infarcts confined to a single lobe, while nine animals sustained infarcts encompassing three lobes, the infarcts of these eleven animals were confined to the cerebral cortex. The three remaining animals sustained infarcts penetrating into subcallosal regions. Thus, results indicate that a detailed investigation of astrocytes, sub populations of astrocytes, other glial cells, and their corresponding secreted neurochemicals will help to clarify the relationships of these cells and chemicals. Furthermore, the technique of microcautry requires refinement in order to produce infarcts that encompass predictable brain regions. A detailed investigation of these cells and secreted chemicals would help to design pharmaceuticals and optimize transplantation of fetal tissue into infarcts as effective modes of therapy.