Expression of glutamate receptor genes in white matter: developing and adult rat optic nerve.

We have identified the glutamate receptor genes expressed by developing and adult rat optic nerve. Results from PCR suggested that of the ionotropic glutamate receptor (GluR) gene family, only GluR1 and GluR3 subunits are expressed by optic nerve. However, Northern blot analysis demonstrated that only the GluR1 subtype is expressed at appreciable levels. In situ hybridization histochemistry of GluR1 was performed and a diffuse pattern of expression was observed in both postnatal day 15 and adult optic nerve. Restriction mapping of the GluR1 PCR product indicated the expression of the flip alternative splice version in optic nerve. The detected GluR1 message was not due to axons because no loss of expression was observed after the degeneration of axons. PCR analysis also revealed the presence of a metabotropic glutamate receptor in optic nerve.