“…This altered state of responsiveness involves long-lasting changes in gene expression, electrophysiological properties, and even morphology of striatal medium spiny neurons (Yao et al, 2004;Thomas et al, 2001;Nestler, 2001;Bibb et al, 2001;Robinson and Kolb, 1997;Koob et al, 1998). Several groups have reported disrupted sensitization to psychostimulants and dopaminergic agonists using pharmacological tools to block NMDA receptor function (Li et al, 1999;Haracz et al, 1995;Kalivas and Alesdatter, 1993;Stewart and Druhan, 1993;Wolf and Jeziorski, 1993;Karler et al, 1989); however, variations in the timing and context of NMDA antagonist administration may affect different aspects of the biological process underlying sensitization (Tzschentke and Schmidt, 1998;Ranaldi et al, 2000).…”