Meeting Abstract
Numerous studies have shown that circulating gonadal steroids are positively correlated with aggression during the breeding season. However, it is becoming increasingly clear that alternative neuroendocrine mechanisms are critical in modulating aggressive behavior, particularly for animals that are more aggressive during the short-day photoperiods (SDs) of the non-breeding season. While previous work from our lab suggests that pineal melatonin (MEL) and the adrenal androgen dehydroepiandrosterone (DHEA) are important in facilitating non-breeding aggression in Siberian hamsters, it is unknown whether local changes in steroid synthesis and metabolism within the brain are ultimately responsible for elevating aggression during the non-breeding season. To investigate the role of MEL in mediating seasonal variation in neurosteroid levels and aggression, we housed male hamsters in long days (LD) or SD, treated them with either timed MEL or saline injections, and quantified aggression after 9 weeks of photoperiodic housing. Furthermore, we assessed whether MEL mediates seasonal changes in steroidogenesis by comparing circulating and neural hormone levels in brain regions that are associated with aggressive or reproductive behaviors using liquid chromatography-mass spectrometry. LD hamsters administered MEL (LD-M) exhibited SD-like levels of aggression. Moreover, LD-M and SD animals reduced circulating DHEA and testosterone levels following an aggressive encounter, whereas LD animals elevated circulating androgen levels. Neurosteroid profiles will also be presented and compared across brain regions and seasonal phenotypes. Collectively, this study provides insight into how MEL regulates seasonal changes in aggression, a behavior that is critical for reproductive success.
