Sex-specific effects of gonadectomy and hormone treatment on acquisition of a 12-arm radial maze task by Sprague Dawley rats - PubMed (original) (raw)

Sex-specific effects of gonadectomy and hormone treatment on acquisition of a 12-arm radial maze task by Sprague Dawley rats

Robert B Gibbs et al. Endocrinology. 2008 Jun.

Abstract

The effects of gonadectomy and hormone treatment on spatial learning were evaluated in adult male and female rats using a modified version of a 12-arm radial maze task. In this version, procedures were used to minimize the effectiveness of strategies less reliant on working and reference memory. Results demonstrate significant sex differences favoring male performance on the working memory component of the task. In contrast, females performed slightly better than males on the reference memory component of the task. In females, ovariectomy produced a decrease in overall accuracy (i.e. an increase in the number of arm entries necessary to obtain all food pellets) as well as declines in working and reference memory performance. Both accuracy and working memory performance, but not reference memory performance, were restored by estradiol treatment. In males, castration impaired working memory performance but did not significantly affect overall accuracy or reference memory performance. Surprisingly, all groups of males performed poorly on the reference memory component of the task, and testosterone treatment appeared to worsen, rather than improve, both accuracy and reference memory performance in males. This may reflect a male preference for certain strategies that were rendered ineffective on this task. Significant sex differences, as well as treatment effects, on arm preference patterns were also detected; however, these differences were not sufficient to account for the effects of sex and treatment on acquisition. Collectively, the data demonstrate robust effects of gonadectomy and hormone treatment on acquisition of this modified radial arm maze task in females, with lesser effects in males.

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Figures

Figure 1

Figure 1

Learning curves showing number of arm entries required by females and males to collect all food pellets on a trial. Data represent group means ±

sem

for each block of training. *, Ovx females differed significantly from both intact and Ovx+E groups (P < 0.05); ¢¢, castrated, testosterone-treated (Cast+T) males differed significantly from gonadally intact controls (P < 0.02 by comparison of marginal group means).

Figure 2

Figure 2

Learning curves showing working memory performance by females and males across six blocks of training. Upper panels show number of WMEs committed during the first six choices of AE2. Lower panels show number of correct choices before making a WME during the first six choices of AE2. Data represent group means ±

sem

. *, Ovx females differed significantly from both intact and Ovx+E groups (P < 0.05); §, Ovx+E differed significantly from both intact and Ovx groups (P < 0.05); ††, Ovx differed significantly from intact group (P < 0.002 by comparison of marginal group means); §§, intact males differ significantly from castrate group (P < 0.05 by comparison of marginal group means).

Figure 3

Figure 3

Learning curves showing reference memory performance by females and males across six blocks of training. Upper panels show number of RMEs committed during the first six choices of AE2. Lower panels show number of correct choices before making a RME during the first six choices of AE2. Data represent group means ±

sem

. *, Intact females differed significantly from both Ovx and Ovx+E groups (P < 0.5); †, intact differed significantly from Ovx group (P < 0.05); §, castrated, testosterone-treated (Cast+T) males differed significantly from gonadally intact controls (P < 0.05); ¢¢, Cast+T males differed significantly from gonadally intact controls (P < 0.01 by comparison of marginal group means).

Figure 4

Figure 4

Graphs summarizing the observed probability of entering an arm based on its relative position to the arm being exited, for each block of training. Shaded areas highlight the peaks. Note that intact males show a strong preference for entering an adjacent arm, whereas intact females show a strong preference for entering an arm located two positions away. Note also that whereas ovariectomy had no effect, estradiol treatment caused females to shift to a male pattern. In contrast, both gonadectomy and testosterone treatment caused males to shift toward a female pattern.

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