Meeting Abstract

P3.103  Saturday, Jan. 5  Role of DHEA in Mediating Seasonal Aggression in Male Siberian Hamsters (Phodopus sungorus). SCOTTI, M.L.*; BELEN, J.; DEMAS, G.E.; Department of Biology, Indiana University, Bloomington, IN 47405, USA ; University of Puerto Rico,Mayag�ez, PR, 00681; Department of Biology, Indiana University, Bloomington, IN 47405, USA mscotti@indiana.edu

Many animals display territorial aggression during the breeding season, an effect traditionally attributed to elevated gonadal testosterone (T). In some species, however, aggressive behavior can persist or even increase during the non-breeding season, a time when T is typically low. Animals that display this �dissociated aggression� suggest the need to consider alternative endocrine mechanisms mediating seasonal changes in aggression. Siberian hamsters, Phodopus sungorus, are an ideal study species for this type of research because they display increased territorial aggression during the non-breeding season (i.e., short days). This increase is inversely related to T levels but may be dependent on adrenal steroid hormones. Thus, the goal of this study was to examine the role of the adrenal steroid dehydroepiandrosterone (DHEA) in the regulation of seasonal aggression in male Siberian hamsters. Specifically, animals were housed in either a long-day (LD) �summer-like� photoperiod or a short-day (SD) �winter-like� photoperiod for 8 weeks. Next, hamsters in each photoperiod received a Silastic capsule filled with either DHEA or an empty capsule. After two weeks, all animals were then tested using a resident�intruder model of aggression. As expected, short-day animals displayed increased aggression compared with long-day animals. DHEA, however, had no effect on aggressive behaviors (e.g., numbers of attack, chase, and latency of initial attack) nor was there a significant interaction between DHEA and photoperiod. Collectively, the results of the present study do not support the hypothesis that seasonal changes in territorial aggression are mediated by DHEA, at least in Siberian hamsters.