Meeting Abstract

65.3  Monday, Jan. 6 09:00  Steroid Synthesis in the Brain SOMA, K.K.; University of British Columbia ksoma@psych.ubc.ca

Endocrinologists have traditionally focused on circulating hormone levels. In the case of steroid hormones, circulating steroids can be locally metabolized within the brain to either more active or less active signaling molecules. Furthermore, the brain can synthesize sex steroids, such as androgens and estrogens, de novo from cholesterol or from inactive precursors in the blood (“neurosteroids”). For such reasons, steroid levels in the blood and brain can differ dramatically. In birds, local steroid synthesis has been implicated in the control of territorial behavior, auditory communication, and neural plasticity. In particular, recent data suggest that aggressive interactions rapidly increase androgen synthesis in the brain of male song sparrows (Melospiza melodia) during the non-breeding season. In contrast, aggressive interactions do not affect circulating androgen levels in the non-breeding season. These data suggest that the Challenge Hypothesis stated by John Wingfield operates at a highly local level in the brain of non-breeding song sparrows.