Chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase in the optic nerve of the monkey (Macaca fuscata): An immunohistochemical study.

An immunohistochemical analysis of the chemoarchitecture of glial fibrillary acidic protein (GFAP) and glutamine synthetase (GS) was conducted in the monkey optic nerve. The optic nerve has been divided into 3 regions: the prelaminar, lamina cribrosa, and retrolaminar regions. However, it currently remains unclear whether the chemoarchitecture of GFAP and GS is homogeneously organized, especially in the retrolaminar region. Strong-to-moderate GFAP immunoreactivity was observed in all 3 regions. The retrolaminar region was further divided into anterior (RLa) and posterior (RLp) retrolaminar regions. More GFAP immunoreactive punctations were observed in the RLa region than in the RLp region. Regarding GS immunoreactivity, moderately GS immunoreactive glial cells were observed in the prelaminar and retrolaminar regions. In the retrolaminar region, there were more of these cells in the RLa region than in the RLp region. GS immunoreactivity was markedly weaker in the prelaminar and retrolaminar regions than in the retina. Thus, the chemoarchitecture of GFAP and GS was heterogeneously organized in the retrolaminar region, and the RLa region was the main GS distribution site in the retrolaminar region. Since GS is a key enzyme of glutamate metabolism, these results may provide clues as to how glutamate is metabolized in the primate optic nerve.