Nicotine, but not cocaine, induces histone hyperacetylation in the striatum. (A and B) Chromatin immunoprecipitation assays for acetylation for (A) histone H3 (K9) and (B) H4 (K5 to K16) at the FosB promoter were performed in animals treated with acute cocaine (30 mg/kg), 7 days of nicotine (10 mg/ml), and 7 days of nicotine followed by acute cocaine (control set at 1, n = 3 to 6 per group). Data represent means ± SEM. (C to F) After 7 days of nicotine or cocaine exposure, protein extracted from striatal lysates was incubated with antibodies detecting histone H3 (K9) (C and E) and histone H4 (K5 to K16) (D and F) tail modifications. *P < 0.05