Effects of antagonizing endogenous oestradiol were tested by treatment on postnatal day (PN) 0 and PN1 with formestane, tamoxifen or vehicle followed by euthanasia at PN2. The mean (± standard error of mean) number of 5-bromo-2-deoxyuridine (BrdU)+ cells on PN2 in (A) CA1, (B) CA3 and (C) dentate gyrus. Females had significantly fewer BrdU+ cells compared to males (ANOVA; #
P < 0.05). Treatment with formestane and tamoxifen decreased BrdU+ cells in males, (*P < 0.01 compared with all other groups).