Aromatase inhibition prevents LTP in the BL of female rats, but not in male rats. A, B, Averaged fEPSP slopes (percentage of baseline) before letrozole wash-in (baseline), after letrozole wash-in (gray arrow), and after HFS in letrozole (red arrow) in amygdale slices from female (A) and male (B) rats. C, Characteristic fEPSPs slopes (asterisks) in females (top) and males (bottom); left, 10 min before letrozole wash-in (gray) and 60 min after letrozole wash-in (black); right, 60 min before (gray) and after HFS in letrozole (black). D, Quantitative analysis of the data from experiments shown in A and B: mixed-factor ANOVA reveals no significant differences between females and males (F(1,12) = 1.5; p = 0.244) but indicates significant differences when letrozole and HFS were applied (F(2,24) = 9.7; p ≤ 0.001). For further differentiation one-way ANOVA was applied, demonstrating significant changes in fEPSP slopes before letrozole treatment, 60 min after letrozole treatment, and 60 min after HFS in the presence of letrozole in males (100 ± 1.3%, 134.7 ± 9%, 156.1 ± 10%; F(2,23) = 4.8; p = 0.019; n = 8, N = 8), but not in females (100 ± 2.3%, 104.9 ± 5.2%, 115 ± 1.1%; F(2,17) = 0.26; p = 0.78; n = 6, N = 6).