Advances in understanding the neurobiology of addiction indicate that not only dopaminergic neurotransmissions but also glutamatergic neurotransmissions within the mesolimbic system play important roles. While the role for the nucleus accumbens (NAc) shell and core in addiction has been extensively studied, the function of the dorsal striatum is not clear. Here, we demonstrate that repeated cocaine injections cause increases ill surface-expressed AMPA receptors in the dorsal striatum. The increased AMPAR expression is more robust in juvenile mice than ill Young adult mice. Furthermore, expression of the G1CT peptide, which prevents the delivery of AMPARs to the surface, attenuates the locomotor sensitization in juvenile mice. Our results strongly suggest that glutamatergic synaptic plasticity in the dorsal striatum may have an important role in behavioral sensitization to cocaine and that there may be different age-dependent control mechanisms. (C) 2008 Elsevier Inc. All rights reserved.