book: Ovarian steroids enhance object recognition in naturally cycling and ovariectomized,...

book: Ovarian steroids enhance object recognition in naturally cycling and ovariectomized, hormone-primed rats [An ... | A.A. Walf, M.E. Rhodes, ...

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	Ovarian steroids enhance object recognition in naturally cycling and ovariectomized, hormone-primed rats [An ... A.A. Walf, M.E. Rhodes, ... Elsevier, 2006 - 11 pages view larger image
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This digital document is a journal article from Neurobiology of Learning and Memory, published by Elsevier in 2006. The article is delivered in HTML format and is available in your Amazon.com Media Library immediately after purchase. You can view it with any web browser.

Description:
Learning and memory processes may be influenced by fluctuations in steroid hormones, such as estrogens and progestins. In this study, we have used an animal model to investigate the effects of endogenous fluctuations in ovarian steroids in intact female rats and effects of administration of ovarian steroids to ovariectomized rats for non-spatial, working memory using the object recognition task. Performance in this task relies on cortical and hippocampal function. As such, serum, cortical, and hippocampal concentrations of estradiol (E"2), progesterone (P"4), and P"4's metabolite, 5@a-pregnan-3@a-ol-20-one (3@a,5@a-THP), were measured by radioimmunoassay. Experiment 1: Rats in behavioral estrus, compared to those in diestrus or estrus, spent a greater percentage of time exploring a novel object concomitant with increases in serum E"2, P"4, and 3@a,5@a-THP levels. Regression analyses revealed that there was a significant positive relationship between E"2 levels in the hippocampus and 3@a,5@a-THP levels in the hippocampus and cortex and performance in this task. Experiment 2: Administration of E"2 and/or P"4 immediately post-training increased the percentage of time spent exploring the novel object and produced levels of E"2, P"4, and 3@a,5@a-THP akin to that of rats in behavioral estrus. Experiment 3: Post-training administration of selective estrogen receptor modulators, including 17@b-E"2, propyl pyrazole triol, and diarylpropionitrile increased the percentage of time spent exploring the novel object compared to vehicle-administration. Experiment 4: Post-training P"4 or 3@a,5@a-THP administration, compared to vehicle, increased the percentage of time spent exploring the novel object and produced P"4 and/or 3@a,5@a-THP levels within the physiological range typically observed for rats in behavioral estrus. Experiment 5: If post-training administration of E"2 and/or P"4 was delayed one hour, no enhancement in object recognition was observed. Together, these results suggest that E"2 and progestins can have mnemonic effects through actions in the cortex and/or hippocampus. mpus.

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