Effects of neonatal corticosterone treatment on maze performance and HPA axis in juvenile rats.

Previous research has indicated that administering corticosterone to dams' drinking water for 21 days produced persistent alterations in physiology and behavior. We investigated whether 4 days of corticosterone exposure would have similar effects, and whether greater effects would be found when corticosterone was administered early in neonatal life than later in neonatal life. Sprague-Dawley dams were given either corticosterone (250 microg/ml) in their water bottles for postnatal days (PND) 5-9 (early corticosterone treatment: ECT), PND 13-17 (late corticosterone treatment: LCT) or no treatment (NT). At the end of treatment, corticosterone levels were higher in pups of corticosterone drinking dams. However, at weaning, ECT and LCT pups had lower basal corticosterone levels than NT pups. As juveniles, ECT pups learned to navigate to a visible and then to a nonvisible platform in a Morris water maze more quickly than did LCT and NT pups. Among females, ECT pups had higher corticosterone release in response to stress than LCT and NT pups. There were no differences in hippocampal corticosteroid receptor levels among the groups. The pattern of results is similar to, but not identical to, that found for pups exposed to corticosterone for 21 days. The results also suggest that there is a critical or sensitive period for corticosterone treatment in that early treatment was more effective than later treatment.

Menstrual cycle variation in spatial ability: relation to salivary cortisol levels.

This study examined whether menstrual cycle phase was associated with performance on the Primary Mental Abilities Test of Spatial Relations, a test of mental rotation, in undergraduate students (N = 82). As cortisol levels also vary across the menstrual cycle under conditions of stress and influence cognitive performance, saliva samples were obtained before and after the test session to examine whether cortisol levels were related to between- and within-group differences in spatial performance. Men scored higher on the spatial test than all the groups of women, although the difference between men and women in the menstrual phase was not significant. Women in the luteal phase scored lower than the menstrual, follicular, and oral contraceptive user groups of women. There were no sex or menstrual cycle differences in cortisol levels, and no association between cortisol levels and spatial performance. The poorer performance of women in the luteal phase was not related to differences in ratings of perceived stress, perceived success on the test, or mood. Although menstrual cycle phase accounted for a significant proportion of the variance (15%) in performance on the spatial test, this does not explain why men outperformed women regardless of the phase of the cycle. Thus, there are clearly several other variables, sociocultural and physiological, involved in mediating individual differences in spatial performance.