Meeting Abstract

29.2  Monday, Jan. 5  Seasonal differences in aromatase (cyp19) mRNA expression in the brain of the free-living male song sparrow, Melospiza melodia morphna WACKER, D.W.*; WINGFIELD, J.C.; DAVIS, J.E.; MEDDLE, S.L.; University of Edinburgh; University of California, Davis; Radford University; University of Edinburgh dwacker@staffmail.ed.ac.uk

Male song sparrows go through three annual life history stages. In the breeding stage, circulating testosterone (T) is elevated and birds are aggressive. During molt, circulating T is basal and birds show little or no aggression. Aggression returns in the non-breeding stage despite low circulating T. Male song sparrows were captured on their territories in the early breeding, molt, and non-breeding stages at multiple sites in Washington State, and brains were collected to assess aromatase (cyp19) expression in nuclei putatively associated with the regulation of aggression. In situ hybridization using an oligoprobe custom created from an existing cyp19 sequence for the Zebra Finch, Taeniopygia guttata was utilized. Male song sparrows had higher levels of cyp19 mRNA in the preoptic area and medial preoptic area/medial division of the bed nucleus of the stria terminalis during breeding as compared to non-breeding and molt. This is consistent with the idea that these areas are involved in estrogen-mediated changes in sexual behavior. Cyp19 mRNA expression did not vary significantly across life history stage in nucleus taeniae or the caudomedial nidopallium. Levels of cyp19 mRNA were higher in the ventromedial hypothalamus in breeding and non-breeding versus molting males, suggesting that this area may be involved in the seasonal regulation of aggression in this species. Together, these finding support a role for cyp19 in the seasonal regulation of reproductive and aggressive behavior in free-living male song sparrows.