Novel NG2 Glial Cells Express NMDA Receptors in the Optic Tract and Lateral Geniculate Nucleus in Primate Glaucoma

Abstract

Purpose:: 1. To determine whether NG2 cells exist in normal and/or glaucomatous optic tract and lateral geniculate nucleus (LGN). 2. To determine whether NG2 cells express NMDA glutamate receptors.

Methods:: Eight monkeys with right eye unilateral experimental glaucoma and three normal control monkeys were studied. Optic tract and LGN were studied for evidence of NG2 immunolabeling. NG2 Chondroitin sulfate proteoglycan-positive immunoreactivity was detected using Super Sensitive Non-Biotin HRP Detection kit (BioGenex., CA, USA). Double-labelling for NG2 and NMDA receptor subunit 1 was performed with immunofluorecence using tyramide signal amplification kit (Molecular Probes, CA, USA). Colocalization studies of dual-color confocal images were analyzed using Manders’ overlap and Pearson’s correlation coefficients.

Results:: In the normal optic tract and LGN, NG2-immunoreactive star-shaped cells with branching processes were detected. In glaucoma, NG2 cells were more easily identifiable in both optic tract and LGN. Colocalization studies in both normal and glaucomatous optic tract and LGN, showed the expression of NMDA receptor subtype 1 in NG2 cells.

Conclusions:: The NG2 glial cells represent a novel cell type in normal and glaucomatous optic tract and LGN. The expression of NMDA glutamate receptor in NG2 cells suggests their role in the glutamatergic system, and neural degeneration in glaucoma.

Keywords: excitatory amino acid receptors • glia • thalamus/lateral geniculate nucleus