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oai:www.ideals.illinois.edu:2142/30933 2023-07-10 col_2142_5131 col_2142_11614 com_2142_5130 com_2142_11613 com_2142_8903

Cognition Medroxyprogesterone Acetate Juraska, Janice M. Juraska, Janice M. Schantz, Susan L. Roy, Edward J. Galvez, Roberto Mahoney, Megan M. Chisholm, Nioka 2012-05-22T00:16:22Z 2012-05-22T00:16:22Z 2012-05 2012-05-22T00:16:22Z 2012-05 Although previous research has indicated that hormone replacement therapy benefits memory in menopausal women, several newer studies have shown no effect or detrimental effects. These inconsistencies emphasize the need to evaluate the role of hormones in protecting against agerelated cognitive decline in an animal model. Furthermore, research has found that ovarian hormones alter brain structure and function. However, many studies evaluating the effects of estrogen and progesterone on brain structure have used young adult animals and have not administered medroxyprogesterone acetate (MPA), the most commonly prescribed progestin. The aging brain may respond differently to the presence of these hormones. Therefore, the effects of long-term hormone treatment during aging on cognition and neuroanatomy were investigated. Female Long Evans hooded rats were ovariectomized at middle age (12-14 months) and placed in one of 5 groups: no replacement, chronic estrogen only, chronic estrogen and progesterone, chronic estrogen and MPA, and cyclic estrogen. Hormone treatment continued until sacrifice. Estrogen was administered in the drinking water. Progesterone and MPA were administered with subcutaneous pellets. Following five months of hormone replacement, animals were tested on a delayed alternation task in the T-maze. Two weeks after completing the T-maze animals were tested in the Morris water maze. At approximately 20 months of age, animals were sacrificed and their brains were sectioned and using immunohistochemistry, stained for tyrosine hydroxylase and synaptophysin. Adjacent sections were Nissl stained to calculate volume and quantify neuron number. The medial prefrontal cortex was examined because it is involved in several cognitive tasks and is known to be sensitive to both aging and ovarian hormones. Using unbiased stereology and light microscopy, neuron number and synaptophysin labeled boutons iii were quantified. Images were acquired of the tyrosine hydroxylase sections using Axiovision (Zeiss) on a fluorescent microscope and fiber densities were quantified. Behavioral results found that animals receiving estrogen in combination with MPA acquired the t-maze faster than no replacement animals, but there were no differences in performance on the delayed portion of the task. However, on the Morris water maze, animals receiving this hormone treatment were impaired as compared to other hormone treated groups. Estrogen in combination with MPA resulted in greater synaptophysin levels in the medial prefrontal cortex. Analysis of tyrosine hydroxylase fibers found that animals receiving estrogen in combination with MPA consistently had significantly higher tyrosine hydroxylase pixel densities than no replacement animals. Hormone treatment did not significantly alter neuron number in the medial prefrontal cortex. These results indicate that the effects of long-term hormone treatment are task specific and longterm hormone treatments alter dopaminergic functioning and synapse number in the medial prefrontal cortex, providing a possible mechanism by which long-term hormone treatments can influence cognition. Importantly, these beneficial neural outcomes were observed in groups receiving estrogen in combination with the controversial progestin, MPA. Item withdrawn by Mark Zulauf (zulauf@illinois.edu) on 2012-04-11T18:49:16Z Item was in collections: University of Illinois Theses & Dissertations (ID: 1) No. of bitstreams: 2 Chisholm_Nioka.docx: 9038489 bytes, checksum: 482b1180685fd827c9c74c6365f126ad (MD5) Chisholm_Nioka.pdf: 1531787 bytes, checksum: f5910e91a79af39ac680fda6ab02c5ca (MD5) Made available in DSpace on 2012-05-22T00:16:22Z (GMT). No. of bitstreams: 3 Chisholm_Nioka.pdf: 1531995 bytes, checksum: 4d532968747536467d2f3b354e504b9f (MD5) Chisholm_Nioka.docx: 9038255 bytes, checksum: 381904068242ffc14b444960896ecbc1 (MD5) license.txt: 4064 bytes, checksum: 27f6d00300362fe40c83e5e2f8872e00 (MD5) http://hdl.handle.net/2142/30933 en Copyright 2012 Nioka Chisholm Aging Estrogen Prefrontal Cortex hormone Treatment Effects of long-term hormone treatment on cognitive behavior and the structure of the medial prefrontal cortex during aging in female rats text Psychology 1299 Psychology 0338 University of Illinois at Urbana-Champaign Dissertation Ph.D. PHD:Psychology -UIUC 10KS0338PHD