In situ hybridization and immunohistochemistry were used to characterize the expression pattern of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors during postnatal development in the rat basal ganglia. All subunit transcripts showed some degree of developmental regulation. GluR1 and GluR2 are expressed at high levels in the neonate with reduced expression in the adult. GluR3 and GluR4 are expressed at significantly lower levels in both neonates and adults and have much more modest degrees of reduced expression in adults as compared with GluR1 and GluR2. Analysis of the flip and flop transcript isoforms indicates that GluR1 flip and flop and GluR2 flip are the predominately expressed splice variants in adults. Observed changes in the expression of the AMPA receptor transcripts indicate that there are fundamental differences in the expression of these receptor subunits in adults and neonates. This phenomenon may play a significant role in the establishment of proper synaptic circuitry within the developing basal ganglia in early postnatal life as well as contributing to differences in susceptibility to injury and disease in the aging brain.