RT-PCR, immunocytochemistry and Western blotting were used to study the expression of the glutamate transporter EAAT4 in the cerebral cortex of cat and mouse. By means of RT-PCR we were able to detect EAAT4 mRNA in the cerebral cortex of both species. Sequencing ensured the specificity of the amplified fragment. Immunocytochemistry and Western blotting enabled us to localize EAAT4 protein in cat and mouse cerebral cortex. Intense EAAT4 immunoreactivity was found in the soma and dendrites of neurons mainly of layers II, III and V. For both species, the signal in the cerebellum was very intense and confined to the molecular and Purkinje cell layer. NeuroReport 12:393-397 (C) 2001 Lippincott Williams & Wilkins.