Hormone treatments reverse stroke-associated declines in cognitive function in a rat model of menopause
Vann, Phillip BS
Yang, Shaohua MD, PhD
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Purpose This study addresses the critical questions important to the future of hormone therapy. The purpose of this study was to provide information on how different durations of hormone deprivation can alter the responsiveness of the brain to ischemic injuries and hormonal therapies. Ultimately, these studies will identify a window of opportunity for treatment with hormones preventing brain dysfunction associated with menopause. Methods Eighty-two Sprague-Dawley retired breeder females rats were ovariectomized (ovx). Twelve or two weeks post-surgery, the rats were implanted with hormone pellets containing cholesterol (vehicle), estrogen (E2) or progesterone (P4), which were replaced every 2 weeks. Two weeks post implantation, the rats received either a sham or ischemic stroke (transient Middle Cerebral Artery Occlusion) surgery. After a one week recovery period, the rats were subjected to a behavioral battery of tests measuring affective (plus maze), motor (rotorod) and cognitive (Morris water maze) function. The rats were then euthanized and brain regions were collected for further biochemical analyses. Data were analyzed using 2- or 3-way ANOVAs followed by pairwise comparisons. Results Treatment with E2 or P4 decreased the time spent in the open arms in both 2 and 12 weeks post-ovx groups. There was no effect of stroke or hormone treatment on the rotorod. For spatial learning and memory, stroke impaired the rats in their ability to learn and retain the location of the platform and impairments were worst in the 12-weeks post-ovx group. E2 and P4 treatment improved performance of the stroke rats in both 2 and 12-weeks post-ovx groups. Conclusions These data suggest that the outcome of stroke is worst as a function of time post-ovx, especially on spatial learning and memory. Hormonal treatment with E2 and P4 were successful in reversing the deleterious effects of stroke on cognitive function. Further studies to identify the mechanisms underlying these observations are underway.