IHC for GFAP (Glial fibrillar acidic protein): This is considered most specific marker for the cells of astrocytic origin that distinguishes differentiated astrocytes from other glial cells.
Use iba1 (500:1) for microglia immunohistochemistry and/or GFAP for the astrocytes labeling. However the GFAP generally do not stain all of the astrocytes as iba1 does it for microglia. For this reason you can use ALDH1L1 as suggested by Lacoste.....