Spatiotemporal dynamics of astroglial and microglial responses after photothrombotic stroke in the rat brain

The effects of photothrombotic stroke in primary somatosensory cortex on astroglial and microglial activation in various regions of lesioned brain were examined at different time points, using immunohistochemistry and lectin binding. The increase in GFAP expression was observed exclusively in the ipsilateral hemisphere, both in the perilesional area and cortical regions distant from the infarct. This remote increase was detectable up to sixty days after the infarct. Transient GFAP elevation was also found in the hippocampus one day after photothrombosis, whereas it was more prolonged in amygdala, as demonstrated at four days after lesion. In contrast to a widespread astrocytic activation, the microglial response was short-lasting and local, confined to lesion and perilesional area. Widespread and prolonged activation of astrocytes after stroke may provide factors promoting slowly developing recovery processes in the whole brain, while microglial response seems to be involved in local repair and removal of cellular debris.