Estrogen dependent activation function of ERβ is essential for the sexual behavior of mouse females

Abstract

We previously generated and characterized a genuine estrogen receptor (ER) β-null mouse line (named ERβ(ST)(L-/L-)) and showed that ERβ(ST)(L-/L-) mice were sterile, due to an ovulation impairment in females and to an unknown reason in males, as their reproductive organs and spermatozoid motility appeared normal. We report here an assessment of the sexual behavior of ERβ(ST)(L-/L-) null mice. We found that ERβ(ST)(L-/L-) males display mildly impaired sexual behavior and that ERβ(ST)(L-/L-) females are significantly less receptive and less attractive than wild-type (WT) females. Decreased attractivity is also exhibited by ERβAF2(0) but not by ERβAF1(0) mutant females (females devoid of either AF2 or AF1 activation function of ERβ). Interestingly, by using an odor preference test, we have determined that the low attractiveness of ERβ(ST)(L-/L-) and ERβAF2(0) females is related to a deficiency of a volatile chemosignal.

Fig. 1.

Sexual behavior of ERβ_ST^L−/L− mutant males. Number of mounts (A) and intromissions (B), mean latencies to the first mount and intromission over three trials (C), duration of first five and last five intromissions (D), time-course of ejaculation (E), and mean latency to ejaculation over three trials in WT and ERβ_ST^L−/L− males (F). Nine WT and 13 ERβ_ST^L−/L− males were used for A–D, and six WT and seven ERβ_ST^L−/L− males (which achieved ejaculation) for E and F. Results are expressed as mean ± SEM, except for E. *P ≤ 0.05 vs. WT (ANOVA results).

Fig. 2.

Sexual behavior of ERβ_ST^L−/L− mutant females. Percentage of mount attempt (A), lordosis quotient (B), latency to the first mount attempt (C), and percentage of ejaculating males (D) in each trial. Eight WT and eight ERβ_ST^L−/L− females were used for (A and D) and eight WT and four, five, and six ERβ_ST^L−/L− for trials 1, 2, and 3, respectively, in (B and C; only females responding by a sexual behavior were considered: 50% in trial 1, 62% in trial 2, and 75% in trial 3). Results are expressed as percentage (A, B, and D) and as mean ± SEM (C). **P ≤ 0.01 vs. WT (Mann–Whitney results in C). *P ≤ 0.05; **, for P ≤ 0.01; ***P ≤ 0.001 vs. WT (χ² tests for A and D). *P ≤ 0.05 ; ***P ≤ 0.001 vs. WT (Student’s paired t test results).

Fig. 3.

Female sexual attractiveness. Number of odor exploration, rears, and grooming episodes (A) and duration of odor exploration and grooming (B) of WT males exploring odors of two C57Bl6/J (ovx and hormone-primed) females. This test was repeated twice by using independent groups of males and females. Number of odor exploration, rears, and grooming episodes (C) and duration of odor exploration and grooming (D) of WT males exploring odors of ERβ_ST^L−/L− and WT females. We performed these experiment with five independent pairs of ERβ_ST^L−/L− and WT hormone-primed females and five independent groups of males. Duration of odor exploration of males exploring odors of ERβ_ST^L−/L− and WT females after repeated progesterone administration (E). Results are expressed as mean ± SEM *P ≤ 0.05 ; ***P ≤ 0.001 vs. WT (Student’s paired t test results).

Fig. 4.

Sexual attractiveness of ERβAF1⁰ and ERβAF2⁰ females. Number (A) and duration (B) of odor explorations of ERβAF1⁰, ERβAF2⁰, and WT females by naïve age-matched WT males. These experiments were repeated twice with two independent pairs of ERβAF1⁰ or ERβAF2⁰ and WT females and two independent groups of naive males. Results are expressed as mean ± SEM ***P ≤ 0.001 vs. control (Student’s paired t test results).

Fig. 5.

Schematic representation of the corridor used for odor preference tests. Illustration of different zones of interest in behavioral evaluation. The wall thickness is 0.5 cm. The size of the different compartments (width x length x height) is given in centimeters. At the extremities, the white areas (9 × 10 × 16 cm) represent the compartments, closed by lids, in which WT or ERβ_ST^L−/L− female and their respective bedding were placed for odor impregnation (odor compartments). The different parameters were scored in the dark gray area (9 × 12 × 16, goal boxes). White and dark gray zones are separated by holed separators (dotted black line). Males are placed in the central black compartment (9 × 10 × 16, start box) before starting the odor exploration test.