Spatial mapping of rapid cell turnover in the reptilian brain

INTRODUCTION: The brain is highly dynamic with many vertebrates displaying brain cell turnover beyond embryological stages. Seasonally breeding animals such as green anole lizards exhibit seasonal differences in brain morphologies, behaviors and circulating sex steroid levels in adulthood. However, how these morphological changes occur remains unclear. This study aimed to understand how brain structures change seasonally by examining the presence of proliferating and dying cells in response to rapid change. METHODS: Nonbreeding males were transitioned overnight into breeding conditions and their behaviors and brains were collected before and 2, 4 and 7 days after transition. Immunohistochemistry was performed to examine activated caspase 3 (AC3; cell death) and bromodeoxyuridine (BrdU; proliferating cells) in the brain. RESULTS: We found significantly more animals displaying BrdU positive cells lining the third ventricles 7 days post-transition. Moreover, a novel reptilian spatial map of AC3-mediated cell death and proliferating cells during this transitioning period was generated. CONCLUSION: The current findings can be utilized to understand neural plasticity in a vertebrate group that is understudied compared to mammals and birds.