Branched chain aminotransferase (BCAT) catalyzes the transamination of the essential branched chain amino acids (leucine, isoleucine and valine) with alpha-ketoglutarate. BCAT exists in two isoforms: one cytosolic (BCATc), mainly expressed in the nervous system, and the other mitochondrial (BCATm), present in a greater number of tissues. We previously showed that BCATc mRNA and protein expression in the dorsal lateral geniculate nucleus of the thalamus is up-regulated by exogenous administration of brain-derived neurotrophic factor (BDNF) following lesion of the visual cortex in newborn rats. Here, we analyzed the expression of BCATc mRNA in the brain of transgenic mice overexpressing the rat BDNF cDNA under the control of the alpha-calcium/calmodulin-dependent kinase II (alphaCaMKII) promoter. In these animals, BDNF is overexpressed in the telencephalon starting from the second postnatal week. RT-PCR and in situ hybridization experiments showed that BCATc mRNA is overexpressed in restricted regions of the cerebral cortex (parietal area) and hippocampus (hilus and CA3 pyramidal cell layer) of adult BDNF transgenic mice respect to wild-type animals. These differences between wt and BDNF mice were not detected in animals of 1 week of age. These results demonstrate that the expression of the BCATc gene in the brain is specifically regulated by BDNF in a time- and region-dependent fashion.