Increased levels of 5MC (a) and 5HMC (b) on Bdnf-iv, -vi, -ix promoter regions in the frontal cortex of PRS mice are reduced by treatment with clozapine (CLZ) but not haloperidol (HAL). Seventy-five-day-old PRS (prenatally stressed) or NS (nonstressed) male mice were treated subcutaneously twice a day for 5 days with vehicle (VEH), 5 mg kg−1 clozapine or 1 mg kg−1 haloperidol. The enrichment of 5MC and 5HMC was measured on the sixth day, 20 h after the last treatment and 2 h after the last behavioral test. The data are expressed as mean±s.e.m. and analyzed statistically with one-way ANOVA followed by Student–Newman–Keuls multiple comparisons. ANOVA for 5MC: Bdnf-iv (F5,30=8.9, P<0.001), Bdnf-vi (F5,30=9.51, P<0.001), Bdnf-ix (F5,30=7.13, P<0.001). ANOVA for 5HMC: Bdnf-iv (F5,30=2.8, P<0.02), Bdnf-vi (F5,30=13.9, P<0.001), Bdnf-ix (F5,30=8.7, P<0.001). *P<0.05 when vehicle-treated PRS samples are compared with PRS clozapine-treated samples or with treated or untreated NS samples. Student–Newman–Keuls multiple comparisons. #P<0.05 when haloperidol-treated PRS samples are compared with PRS clozapine-treated samples or with treated and untreated NS samples. Student–Newman–Keuls multiple comparisons. ANOVA, analysis of variance; BDNF, brain-derived neurotrophic factor; 5HMC, 5-hydroxymethylcytosine; 5MC, 5-methylcytosine.