Schematic representation of the treatment paradigms.

Maternal behavior was independently examined after hormonal treatments according to three paradigms. Paradigm 1: after OVX surgery, a progesterone capsule was implanted for 4–10 days. Simultaneously upon removal of the progesterone capsule, EB- or vehicle-containing capsules were implanted for 2 h, 3 days, or 7 days. Maternal behavior was then analyzed. Paradigm 2: hormonal treatment was the same as for 3 days EB treatment in paradigm 1. The difference from paradigm 1 was the use of familiar pups from communal nests for behavioral analyses. Paradigm 3: ten days after OVX surgery, mice were intraperitoneally injected with letrozole for 4 days. Four hours after the final treatment, maternal behavior was analyzed.