Taurine immunoreactivity (IR) in 1 -μm sections of glutaraldehyde-fixed human optic nerve was observed using light microscopy and an antibody raised in rabbit to taurine conjugated to bovine serum albumin. Throughout the nerve, taurine-lR was prominent in glial cells, in their perinuclear regions, and in their numerous branching processes, some of which extended to the pial septa. The peripheral glial mantle (glia limitans) was densely stained, whereas axons and the pial septa showed relatively little or no taurine-IR. Immunoreactivity for glial fibrillary acidic protein (GFAP), an astrocyte-specific marker, was evaluated on adjacent sections. The pattern of GFAP-IR was highly similar to that for taurine, suggesting that a subset of taurine-immunoreactive glial cells are optic nerve astrocytes. To our knowledge, this is the first localization of taurine and GFAP in human optic nerve.
