Sex-related differences in spatial learning during the early postnatal development of the rat

Some authors have reported that male rats younger than 21 days old are unab le to perform spatial learning correctly because they have still not develo ped the ability to use extra-maze cues. In experiment 1, we analyzed spatia l learning in 14-, 21-, 30- and 42-day-old rats using the Morris water maze (MWM). According to our results, a good performance was observed in 30-day -old male rats whereas this was not observed in female rats until they were 42 days old. In experiment 2 we studied the role of sex hormones in this k ind of learning using the MWM and 30-day-old rats (castrated male rats and female rats treated with testosterone propionate (TP) after birth). The lat ter group, the male control group and the castrated males all solved the ta sk correctly. The objective of experiment 3 was to determine possible diffe rences between the sexes in the use of taxon strategies in the T water maze . To summarize, sexual dimorphism was only observed in spatial learning dur ing development. (C) 1999 Elsevier Science B.V. All rights reserved.