Age-related declines of androgens and libido in males have been
observed for decades. This dissertation sought to elucidate the mechanisms by
which hormones may act differentially upon their receptors in the hypothalamus
of aging compared to young males. I also examined how sexual experience
modulates the ability of hormones to facilitate sexual behavior with aging.
Experiment one measured androgen receptors (AR) and estrogen receptor α
(ERα) cells in male rats at young, middle-aged and old age. I found that AR cell
numbers in hypothalamic regions studied underwent significant age-related
increases. Numbers of heavily ERα labeled cells, but not total ERα cells,
increased with age. This study demonstrates that the aging brain has the capacity to synthesize hormone receptors which is increased possibly due to
decreased testosterone concentrations. Experiment two examined the effect of
sexual experience on serum hormones and cells of AR and ERα in hypothalamic
regions in young and middle-aged males. The results showed that AR cell
numbers increased with aging but did not change with experience. No age- or
experience-related alteration in ERα expression occurred. However, serum
testosterone increased and estradiol decreased with age. Experience increased
total and free testosterone. Interactions of age and experience on total
testosterone, estradiol, and luteinizing hormone were found. These results show
long-lasting effects of sexual experience on hormones, but not on their receptors
in the hypothalamus. Experiment three investigated effects of exogenous
testosterone on sexual behavior in young and middle-aged males. The results
showed a decline in sexual behavior parameters with age. After castration with
testosterone treatment, there were few differences in sexual behavior measures
between young and middle-aged males. AR cell numbers were higher and ERα
cell numbers lower in testosterone compared to vehicle-treated males of both
ages, and few effects of age occurred. These findings indicate that testosterone
and aging interact in a complex manner to control numbers of cells expressing
hormone receptors in the brain and on the subsequent control of sexual
behavior. This insight provides a better understanding of the relationship
between molecular changes in the brain and behavior, and suggests new therapeutic targets to human testosterone treatment. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/6639 |
| Date | 23 October 2009 |
| Creators | Wu, Di |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Format | electronic |
| Rights | Copyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works. |
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