Figure 1.

Experimental design used to study the effects of age, timing, and duration of hormone treatment. Ovariectomy (OVX) surgery, followed by vehicle (VEH) or estradiol (E₂) capsule implantation, was performed at age 4–5 [mature (MAT)] and 11–12 months [aging (AG)]. Animals in groups 1–6 were MAT or AG rats that were given VEH or E₂ for 3 or 6 months. Animals in groups 7 and 8 were AG rats that were given VEH or E₂ post-OVX and then switched after 3 months to the opposite treatment for an additional 3 months. Comparisons between groups 1–4, 3–6, and 5–8 were made as described in Section “Materials and Methods.” Figure adapted from Ref. (16).