Glial cells in the mammalian central nervous system, like neurons, possess glutamate receptors suggesting that neuronal-glial communication via neurotransmitters is an important component of brain function. In the bovine corpus callosum, GLUR-1, an alpha-amino-3-hydroxy-5-methyl-4 isoxazolepropionate (AMPA)/kainate receptor subtype, is a major type of glutamate receptor. It is distributed along astrocytic processes and it is particularly abundant in the end-feet and the glial fibers surrounding the capillaries. This close spatial relationship between GLUR-1 receptors in astrocytes and endothelial cells suggests that these receptors may be activated by glutamate transported across the blood-brain barrier and thus regulate the barrier itself by ensuing astrocyte-endothelial cell interactions.