Steroid hormones are critical for proper brain development, as well as the expression of sexual behaviors in adulthood. In the brain, testosterone (T) can be metabolized into estradiol via the action of the aromatase enzyme, or 5α-dihydrotestosterone via the action of the 5α-reductase (5αR) enzyme. Aromatase and 5αR are critical for sexual behaviors in a variety of species, including the green anole lizard. In this dissertation, I began to evaluate the hypothesis that T regulates its own metabolism in the brain of green anoles. I tested this idea using two types of experiments: comparisons across groups of animals under naturally varying T levels and gonadectomized animals with or without hormone replacement. In Chapter 1, I examined the whole brain activity of aromatase and 5αR in gonadectomized males and females that were treated with either a T- or blank-capsule. In Chapters 2 and 3, I cloned the anole-specific aromatase and both isozymes of 5αR (5αR1 and 5αR2) and examined their expression in the brain. In Chapter 4, I described the expression of aromatase and 5αR2 in the forebrain of gonadectomized males and females that were treated with either a blank or T-filled capsule. Finally, in Chapter 5, I examined aromatase, 5αR1, and 5αR2 expression at two different stages in development. This body of work has expanded knowledge on steroid metabolizing enzymes to a reptilian species, and begun to address the idea that T can influence its own metabolism in multiple vertebrate taxa.
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