Spatial and nonspatial learning across the rat estrous cycle.

Recent evidence has demonstrated that there are fluctuations in both the anatomy and physiology of the hippocampus across the estrous cycle of the female rat. In the present study we examined the behavioral implications of these changes by testing females on either a hippocampal or nonhippocampal version of the Morris water maze during the various phases of the estrous cycle. Males were also tested on these tasks. Although there was little variance on the nonhippocampal cue task, females in proestrus performed significantly better than those in estrus. Optimal female performance on the spatial version of the task occurred during the phase of estrus, whereas the least efficient performance occurred during proestrus. These results do not support the traditional view that hippocampal long-term potentiation is positively correlated with spatial learning.