(A) Time-line for Experiment 1. Rats received 8 daily injections of cocaine (Coc; 15 mg/kg, i.p.) or saline (Sal) in photocell cages. (B) Locomotor data (from animals used to generate whole NAc tissue) showing development of sensitization (main effect of injection day for cocaine group: F1,80=13.28, P<0.01; Bonferroni t-tests comparing individual time-points, *P<0.05; n=6/group). (C) Comparison of summed photocell counts demonstrating locomotor sensitization in a separate cohort of identically treated animals used to generate core and shell samples [main effect of injection day: F1,29=5.28, P<0.05; Bonferroni t-tests indicated a significant effect within the cocaine group (*P=0.01) but not the saline group; n=16 Sal, n=15 Coc]. (D–F) On withdrawal day 14, nitrosylation of stargazin was measured as described previously (Selvakumar et al., 2009) in whole NAc samples obtained from one cohort of rats (behavioral data shown in panel B) and in core and shell samples obtained from a different cohort of rats (behavioral data shown in panel C). Stargazin nitrosylation was significantly greater in whole NAc (D) (t3=5.84, *P<0.05) and NAc shell (F) (t6=2.48, *P<0.05) of cocaine-sensitized animals, with no difference in the NAc core (E).