Fig 1.
In Experiment 1, mice received a single s.c. injection of either oil vehicle (control, 0.1 ml sesame oil) or various doses (0.5 μg/0.1 ml, 5 μg/0.1 ml, or 50 μg/0.1 ml) of EB 7 days post-ovariectomy. Fear conditioning was conducted 2 days after EB treatment, and the mice were tested for their conditioned fear responses the following day. In Experiment 2, mice were ovariectomized and implanted s.c. with a Silastic capsule (I.D. 1.98 × 20.0 mm) containing either vehicle or various doses (0.05 μg, 0.5 μg, 5 μg, 50 μg/0.1 ml) of EB. Two weeks post-implantation, fear conditioning and testing were conducted. In the conditioning phase, 3 min after being placed in the chamber, mice were administered three consecutive foot shocks (duration: 2 s, 0.8 mA) with 30 s intershock intervals. The day after the last behavioral test, the animals were sacrificed using a pentobarbital overdose. The uteri were collected and the wet weights were recorded. In Experiment 3, mice were ovariectomized and implanted (s.c.) with a Silastic capsule (I.D. 1.98 × 20.0 mm) containing either vehicle or various doses (0.05 μg, 0.5 μg, 5 μg, 50 μg/0.1 ml) of EB. Two weeks post-implantation, the animals were decapitated and their trunk blood was collected for the hormonal assay.
Fig 2.
Effect of freezing and locomotion durations on contextual fear conditioning in Experiment 1.
OVX mice received a single s.c. injection of EB at a dose of 0.5 μg/0.1 ml (EB0.5S), 5 μg/0.1 ml (EB5S), or 50 μg/0.1 ml (EB50S), or an oil vehicle (EB0S) two days before conditioning. The mean (± SEM) duration of freezing (A) and locomotion (B) in the 10-min test conducted 24 h after conditioning is shown. Mice treated with a high dose of EB (EB50S) displayed significantly more freezing than control and EB5S mice (p < 0.05). Significant differences are denoted by an asterisk; *p < 0.05.
Fig 3.
Effect of freezing and locomotion durations on contextual fear conditioning in Experiment 2.
OVX mice were implanted s.c. with a Silastic capsule containing either vehicle (EB0L), 0.05 μg/0.1 ml (EB0.05L), 0.5 μg/0.1 ml (EB0.5L), 5 μg/0.1 ml (EB5L), or 50 μg/0.1 ml (EB50L) 14 days before conditioning. Mean (± SEM) duration of freezing (A) and locomotion (B) in the 10 min test conducted 24 h after conditioning. Mice treated with EB50L showed a significantly longer freezing time compared with control (p < 0.05) and EB5L (p < 0.05) mice. EB50L mice also displayed a significantly shorter locomotion time compared to control mice (p < 0.05). Significant differences are denoted by an asterisk; *p < 0.05.
Table 1.
Uterine weight.