Meeting Abstract
The Organizational/Activational Hypothesis states, exposure to androgens early in development organizes the male brain so that, as an adult, the same hormone elicits the expression of male reproductive behaviors. However, in the past several decades, studies have indicated that estrogens, aromatized from androgens, and not the direct action of androgens, may be critical for organization of the male brain. The presence of estrogens during prenatal and perinatal brain development has been shown to stimulate cell growth and promote the formation of neuronal and sex-specific pathways. It is believed that the estrogens that influences CNS development is derived from neuronal estrogen synthesis (aromatization) rather than estrogens found in the circulation. In a recent study, we found that estrogens appeared to be the active hormone regulating courtship and mating in the male red-sided garter snake (RSGS). Consequently, if estrogen is the hormone activating courtship and mating in male RSGSs, estrogens should also be responsible for organizing the male RSGS brain. We tested our hypothesis by examining the brains of newborns, 3, 6, and 9 month old RSGSs, raised under natural conditions in our lab, and wild-caught immature and juvenile RSGSs for the presence and distribution of aromatase immunoreactive (ARO-ir) neurons and estrogen receptors (ER) as indicators of brain development. Preliminary results support an age related progression where ARO-ir neurons and ERs, absent in newborns could be found in the brains of juvenile RSGSs.
