1. Testosterone SONG

2. T is elevated during periods of elevated aggression

3. T implant increases song rate Hunt et al, 1997

4. T receptors found in song system

5. T is usually elevated during periods of elevated aggression

6. Seasonal Changes in Aggression, T and E2 ? Wingfield & Hahn, 1994

7. aromatase Block hormone synthesis or hormone receptor, measure song • Song Sparrows in Fall • Treatment: • Flutamide: blocks androgen receptor • ATD: blocks aromatase • Test • Play song on birds territory to Simulate Territorial Intrusion • Measure Song production in response Soma et al, 1999

8. Song Sparrows in Fall Treatment: Control (vehicles) Fadrazol: another aromatase inhibitor Fadrazol + estrogen Rescue effect? aromatase Estrogen or Testosterone? + E2 Soma et al, 2000

9. E2 receptors found in song system

10. aromatase Neurosteroid Hypothesis • Steroid precursors released from adrenal or gonad • Made into active steroids in the brain DHEA Soma and Wingfield 2001

11. HVC volume aromatase Song production DHEA Effects of DHEA? Soma et al, 2002, 2004

12. Why Neurosteroids?

13. -DHEA is elevated in spotted antbird -DHEA increases during aggressive encounters