We have investigated the presence and distribution of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) preferring glutamate receptor subunits GluR1-4 in glial cells of the adult bovine corpus callosum, optic nerve and fornix. To this end, reverse transcription and polymerase chain reaction (RT-PCR) analysis and immunohistochemical experiments were carried out using specific primers and antibodies for each subunit. In the three areas studied, we observed that the main subunits expressed were GluR1-3 and that they were present in the majority of astrocytes. These subunits were located throughout the cell body and processes of fibrous astrocytes and were particularly rich in endfeet and in the glial adventice surrounding the capillaries. In addition, we also observed by immunohistochemistry that the GluR4 subunit was present in a small subpopulation of cells which, based on their morphological and antigenic features, may correspond to immature cells of the oligodendroglial lineage. These results demonstrate a differential expression of AMPA-selective glutamate receptor subunits with respect to glial cell type and raise the possibility that the expression of particular subunits may be associated with specific functions in adult white matter glial cells.