Effects of ovarian hormones and environment on radial maze and water maze performance of female rats

The effects of gonadal hormones and environment on performance in an eight- arm radial maze and in the Morris water maze were determined in female rats . Long-Evans female rats were ovariectomized or sham ovariectomized at 35 d ays of age, and housed in complex environments or in isolation for the dura tion of the study. One month following surgeries, spatial working memory pe rformance in the radial maze was assessed. Exposure to complex environmenta l conditions independently enhanced performance, as indicated by increased arm choice accuracy during 20 days of maze training. Additionally, gonadall y intact females significantly outperformed ovariectomized females before c yclicity was disrupted by food deprivation. Following radial maze training, spatial reference memory performance was assessed in the same females util izing the Morris water maze. Gonadally intact females housed in isolation p erformed significantly more poorly during 16 days of place training trials and displayed significantly shorter times in the platform quadrants and few er target crossings during probe trials than gonadally intact and ovariecto mized females housed in complex environments and ovariectomized rats housed in isolation. Consequently, acquisition and retention of the water maze wa s impaired by the presence of ovaries, and this impairment was counteracted by exposure to complex environments. Performance did not differ between gr oups on cued trials, indicating that sensorimotor and motivational function s did not differ between groups. Results of these experiments indicate that endogenous gonadal hormones can differentially affect performance on tasks of spatial working and spatial reference memory, and that environmental co nditions can interact with gonadal hormones to affect behavior. (C) 1999 El sevier Science Inc.