Article Figures & Data
Figures
- Fig. 1.
Design of the experiment and group treatment.Sham, Control rats with sham surgery in which ovaries were spared. OVX, Ovariectomized rats. E, Treatment with 17β-estradiol: i, acute, with injections; m, chronic, with implants. Injections of SCOP were applied during periods 4 and 5.
- Fig. 2.
The schedule of 17β-estradiol injections. One set consisted of the three injections as shown in the figure. Ovariectomized rats (group OVX2) received four sets of injections.
- Fig. 3.
The dynamics of body weight in control (sham surgery, open squares) and experimental [ovariectomized OVX1 (gray circles) and OVX2 (open triangles) ] groups of Fischer-344 rats during periods 1–7 of behavioral testing. A decrease in body weight during every period was attributable to food deprivation during testing in the DNMP task. Note that OVX rats gained weight compared with Sham rats, and this effect of ovariectomy was abolished quickly by both types of estrogen treatment (injections and implants).
- Fig. 4.
Plasma level of estrogen in Sham (diestrus) and OVX rats during behavioral testing (periods 1–7). The gray bar indicates the level of estrogen 1 hr after injection of 10 μg of 17β-estradiol (OVX2 group, open triangles). The plasma estrogen concentration tested 5 d after implantation of pellets with 17β-estradiol was similar in both OVX1 (period 6, open squares) and OVX2 (period 7) groups. The level of estrogen slightly decreased when tested 1 month after implantation (OVX1group, period 7). Filled circles, Sham.
- Fig. 5.
Aging-related changes in working memory tested in the DNMP task. Each point represents the average percentage of correct arm choices per group. Only sessions with regular, short-delay trials and without SCOP treatment are shown. The dashed linefor the OVX2 group (open triangles) indicates the age-related decline before the estrogen treatment. Thecaret indicates the onset of the age-related decline in the appropriate group as a result of a post hoc test (p < 0.05). The asteriskindicates a significant difference from the OVX1 group (open circles) during the period (simple main-effect ANOVA; p < 0.05). Open squares, Sham.
- Fig. 6.
Delay sensitivity of working memory in Sham (open bars) and OVX (shaded bars) rats.A–C represent the average percentage of correct arm choices in trials with different delays. D–F represent the maximum of consecutive correct choices. Asterisksindicate significant effects of ovariectomy as a result of a simple main-effect ANOVA (p < 0.05).
- Fig. 7.
Effect of systemic SCOP (Sc) administration on the accuracy of correct arm choices in OVX (gray circles) and Sham (open squares) groups (19-month-old rats, 6 months after ovariectomy). The inset shows the effect of the lowest dose of SCOP tested 1 month later. Note that OVX rats that received estrogen treatment (group OVX2) were still more sensitive to SCOP than Sham rats. Single anddouble asterisks indicate a significant SCOP-induced decline as a result of a post hoc test applied to the significant effect of dose in the OVX group (p < 0.01 or 0.001, respectively). A decline in the performance of Sham rats did not reach significance (p > 0.07). The pound signindicates a significant effect of SCOP as a result of a one-way, repeated-measures ANOVA (p < 0.05).
- Fig. 8.
Effect of 17β-estradiol injections (A) and implants (B) on ovariectomy-induced deterioration in working memory. The accuracy of correct arm choices in control (Sham) rats is shown as 100%.A, Ovariectomized rats that received repeated injections of estrogen (group OVX2+Einjections, gray bars) improved their performance to a level similar to that of control rats. The performance of ovariectomized rats that did not receive estrogen replacement (OVX1, striped bars) deteriorating further during the testing (period 5). Theasterisks indicate a significant difference from control rats (p < 0.05). B, The treatment with estrogen implants was more effective in improving the performance of ovariectomized rats if treatment was preceded by estrogen injections (group OVX2, gray bars). The asterisk shows a significant increase in choice accuracy as an effect of estrogen implants; thearrow indicates a significant difference between OVX1 (striped bars) and OVX2groups in choice accuracy between 5 and 9 d after implantation (p < 0.05). The triangleindicates the higher performance of the OVX2 group compared with the OVX1 after a longer period of estrogen treatment; however, because the exact duration of the treatment was different in the OVX1 and OVX2 groups, the difference was not statistically determined.
- Fig. 9.
Performance of Sham and ovariectomized (groups OVX1 and OVX2) rats in platform (A) and probe (B) trials of the place discrimination task. The dotted line inB indicates chance level. The average speed of swimming during platform trials is shown in C. For treatments of OVX1 (gray circles) and OVX2 (gray triangles) groups, see Figure 1. Pound signs indicate a significant improvement in place discrimination attributable to retesting compared with period 1 (post hoc test applied to a significant effect of period; p < 0.05).Asterisks indicate a significant difference between control and ovariectomized rats (OVX1 and OVX2) as a result of a post hoc test applied to a significant effect of group (p< 0.05). Open squares, Sham.
- Fig. 10.
The preference for the quadrants with and without the platform tested after the first (A) and second (B) session in the repeated acquisition task. Each bar indicates the time spent in the quadrant with the most recent platform location (mean ± SEM). The time spent in the quadrant with a previous platform location is indicated as a marker (mean).Thick lines indicate a range of preferences for two other nonplatform quadrants. The previous correct quadrant for session 1 was a quadrant with a platform location used in the place discrimination task. See Figure 1 for treatments for the OVX1 and OVX2 groups. Significant between-groups differences in the preference for the correct quadrant were revealed only in the first session, in which a change in the platform location coincided with partial changes in spatial cues.Asterisks indicate a significant difference from Sham rats as a result of a post hoc test applied to a significant effect of group (p < 0.05).
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