Date Available

1-10-2013

Year of Publication

2013

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Medicine

Department/School/Program

Physiology

First Advisor

Dr. Melinda E. Wilson

Abstract

Estrogens, such as the biologically active 17-b estradiol (E2) have many actions in the male and female brain. Not only does E2 regulate reproductive behavior in adults, it organizes and activates the brains of younger animals in a sex-specific manner. In addition, many human studies have shown E2 to provide protection against a variety of neurological disorders, including stoke. These studies have been controversial and depend largely on the type and timing of hormone replacement. Animal studies are much less controversial and clearly demonstrate a neuroprotective role for E2 following ischemic brain injury. Because much of E2 neuroprotection requires sex steroid hormone receptors, it is essential to understand expression patterns of these receptors. For the current studies, I evaluated estrogen receptor alpha (ER α), estrogen receptor beta (ER β) and androgen receptor (AR) expression in the cortex. It is known that these receptors change in expression at several times in an animal’s life span including during early postnatal development and following ischemic brain injury. Here I used an in vitro cortical explant model to further examine how these receptors change both during development and following injury. This in vitro model is important because it provides a way to investigate changes in receptor expression pattern in the cortex without input from other brain regions. In addition to characterizing this model, I also evaluated the contribution of E2 to changes in receptor expression and on cell death following injury in the explants. To begin to decipher mechanisms for E2 mediated neuroprotection, I added antagonist for each of the receptors before and after injury. In each these experiments, I also examined potential sex differences by separating the female and male brains before I cultured the explants. Overall, these experiments showed that cortical explants are a good in vitro model. Here we found that E2 was protective in female, but not male cortical explants following injury. However, the exact mechanisms of E2-mediated neuroprotection are still to be deciphered.

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