Steroid Hormone Induced Plasticity in the Forebrain Region of Green Anole Lizards

Testosterone has distinct effects on seasonal brain morphology and behavior. Our animal of interest, the green anole lizard, Anolis carolinensis, is known for reproductive displays such as extension of the dewlap, a red throat fan, aggressive behavior such as defending territory against other males, and pushups. These behaviors are observed during the breeding season, but not in the non-breeding season. Forebrain areas that are being studied include the preoptic area (POA) which facilitates masculine reproductive behavior under androgen treatment, and the ventromedial hypothalamus (VMH) which facilitates female reproductive behavior. These areas are also known to change volume seasonally, but the specific mechanism is unknown. Our experiment seeks to understand the mechanism by which steroid hormones act on nuclei in the forebrain to induce seasonal differences. Our experiment was conducted on gonadectomized breeding season males. Steroid hormones were then introduced through a long acting implant, supplying testosterone, DHT, estradiol, or vehicle. We expect to see soma size and cell proliferation in steroid hormone treated lizards to be restored to breeding season levels within the POA and the VMH, as has been shown in previous work. Future studies may include measuring the distances between neurons, dendritic branching, or glial cell counts, which may explain changes in brain area volumes. It is likely that steroid hormones are critical for maintenance of breeding season morphology; however, it is also predicted that there may be other factors contributing to soma size and cell proliferation