Resumo

Objectives: The present study investigated if reproductive experience and maternal care interferes with later performance in reference (RM) and working memory (WM) versions of the Morris water maze tasks. Material and Methods: Independent groups of 90-day old female Wistar rats that (1) gave birth and remained with their pups until weaning (Primiparous, N=12 subjects), (2) were virgins but fostered newborn rats along 21 days, thus exhibiting typical maternal behaviors (Foster, N=9), and (3) were virgins and had no maternal experience (Controls, N=12), were tested in reference (RM) and working memory (WM) versions of the Morris water maze task 7 days after weaning. In the RM task, the hidden platform was maintained in a single fixed location along 12 consecutive days; there were 2 trials per day and the intertrial interval (ITI) was 10 min. Then, 3-min duration Probe Tests, with the platform removed, were run 24 and 48h after the last RM session; score analysis considered three 1-min Time Bins. WM was assessed by exposing the subjects to 3 trials per day, varying the platform location every day. While on days 1 to 5 the ITI was=5 min, on days 6 to 10 it was 15 min. Results: In the RM task, ANOVA revealed no significant main effects for latency, path length and time percentage within training quadrant. However, ANOVA revealed a significant Group X Session X Trial interaction effect for both latency and path length (F(22, 330)=1,73 - 1,91; p < 0,03); post-hoc tests showed that Foster females exhibited greater improvement from trials 1 to 2 at the early sessions relative to that seen for Primiparous and Control females. In the Probe Test ANOVA revealed no significant Groups differences for percentage of time spent within training quadrant. In contrast, ANOVA revealed a significant Group x Time Bin interaction effect for percentage of time spent within the former platform location (F(4, 60)=2,76, p=0,035); Foster females exhibited quicker extinction in their search for the platform relative to Primiparous and Control females. In WM test, ANOVA revealed no significant Group effects for latency and path length. However, percentage of time spent within the day-before platform location exhibited a significant Group X Trial interaction effect (F(4, 60)=3,1834, p=0,014); post hoc analysis showed that Foster females exhibited a quicker extinction of their search at the former platform location as compared to the remaining groups. Conclusions: Foster females seem to have exhibited quicker acquisition and greater behavioral flexibility in dealing with the requirements of the tasks employed as compared to Primiparous and Control females.