GFAP and ocular hypertension: Recently, we demonstrated that glial fibrillary acidic protein (GFAP) immunoreactivity as well as neuronal cell loss was increased in the LGN of cynomolgus monkeys at 4 months after unilateral ocular hypertension [7], and that microglial activation was detectable by positron emission tomography (PET) imaging with [11C]PK11195, a PET ligand for the peripheral-type benzodiazepine receptor (PBR), at 4 to 12 months after unilateral ocular hypertension [8].