Sexually dimorphic cognitive style in rats emerges after puberty

In a water maze (WM), rats employ different and sexually dimorphic behavior al strategies to solve a place-learning task, a test of cognitive/propositi onal ability. Puberty is the last step in brain development and marks an im portant phase with regard to sexually dimorphic cognitive performance and b ehavior. The present study assessed possible sex differences in cognitive s tyle before and after puberty in a WM place-learning task. Since nitric oxi de (NO) is implicated in spatial learning and hippocampal function, and sin ce brain NO2- + NO3- levels (stable metabolites of NO) display region-speci fic sex differences in rat brain, NO2- + NO3- levels were determined after behavioral testing. The sex-related style difference emerged very clearly b ut only in the adult rats, which suggests that the female behavioral strate gy in the WM place-learning task requires the presence of female sex hormon es at puberty. Although NO2- + NO2- levels were higher in the adult rats an d males compared to prepubertal and female rats, respectively, no significa nt correlations emerged between brain NO and behavior. The fact that the be havioral sexually dimorphic cognitive-style effect observed here and in pre vious studies appears to emerge only after puberty suggests that awareness of such postpubertal sex differences may also be important in human educati onal and therapeutic contexts. (C) 2000 Elsevier Science Inc.