Female rats have

a 4- to 5-day cycle over which estrogen and progesterone levels change fairly dramatically. Proestrus is a stage prior to ovulation when estrogen levels are relatively high. When trained during this stage, females learn faster and condition more than females in other stages.11 These data suggest that estrogen is positively related to performance of this associative learning task. How do these results compare to others in Inhibitors,research,lifescience,medical the literature? Certainly, there are numerous reports that learning (or performance) is related to the presence of sex hormones,12-15 although these effects vary depending on task and species. Women tested during the phase of the menstrual cycle associated with high levels of estrogen score better Inhibitors,research,lifescience,medical on tests of verbal fluency and fine motor skills – tests that, women already perform well relative to men.1,16 In rats, females tested during proestrus perform poorly during a spatial memory task that is dependent, on an intact, hippocampal formation, but perform optimally when the task is not dependent on the structure.17 Some report, that females tested

during estrus have deficient spatial performance relative to males and females in other stages,18 whereas Inhibitors,research,lifescience,medical others report no effect of estrous cycle on learning, though performance variables were affected.19 Some of these effects can be ameliorated by previous familiarization with the task demands,20 suggesting that the stressful nature of some of these tasks contribute to the seemingly

variable Inhibitors,research,lifescience,medical responses. Given the variation in the task demands, the brain structures involved, as well as the cyclic nature of endogenous Tofacitinib mechanism hormone levels, it should come as no surprise that the relationship between absolute levels of hormones and learning is inconsistent. Moreover, since hormone levels do vary so selleck catalog frequently over time and experience, their effect on learning could not. be absolute. Rather, hormones modulate learning to varying degrees via. numerous mechanisms and presumably for numerous adaptive reasons. Sex-specific responses to Inhibitors,research,lifescience,medical stress and memory formation As with learning, there are sex differences in the stress response Brefeldin_A and these effects are often a matter of degree, not. direction. The most robust, sex difference occurs with endogenous levels of glucocorticoids. In many species, glucocorticoid levels are higher in females than males.21,22 This sex difference is apparent, under unstressed and stressed conditions and in rats, glucocorticoid levels are elevated in females during proestrus relative to other stages of estrus. Stressful experience can also elicit very different, behavioral responses in males versus females. For example, we have shown that female rats exposed to an acute stressful event are severely handicapped in their ability to learn an associative response.