Meeting Abstract
Many vertebrates exhibit distinct life-history stages that are associated with specific physiological and behavioral functions, such as reproduction, migration, and foraging. In seasonal organisms, resource availability relegates these life-history stages to a specific time of year, and therefore seasonal transitions between life-history stages are often accompanied by dramatic changes in both physiology and appetitive and consummatory behavior. Red-sided garter snakes (Thamnophis sirtalis) are an exceptional model for understanding the mechanisms mediating life-history transitions. We previously found that glucocorticoid hormones play a central role in the seasonal transition from reproduction to migration and foraging. We now aim to understand the mechanisms by which changing glucocorticoids mediate these behavioral shifts. Here, we present data describing interactions between glucocorticoids and two neuropeptides that induce potent and rapid changes in reproductive and feeding behaviors: arginine vasotocin (AVT) and neuropeptide Y (NPY). Both AVT and NPY change seasonally in male snakes, and the seasonal changes are specifically associated with the transition from reproductive condition to foraging. Further, experimentally decreasing plasma glucocorticoids with a synthesis inhibitor prematurely induces feeding behavior and also increases NPY-immunoreactivity in specific brain regions. Finally, prior studies show that exogenous NPY significantly increases feeding behavior, and our preliminary data suggest that AVT both elevates plasma glucocorticoids and increases male courtship. Collectively, these studies begin to elucidate how glucocorticoids interact with neuromodulators to induce the motivational trade-offs associated with complex life-history transitions.
