Testosterone SONG

T is elevated during periods of elevated aggression

T implant increases song rate Hunt et al, 1997

T receptors found in song system

T is usually elevated during periods of elevated aggression

Seasonal Changes in Aggression, T and E 2 Wingfield & Hahn, 1994 ?

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 aromatase Block hormone synthesis or hormone receptor, measure song

Estrogen or Testosterone? Song Sparrows in Fall Treatment: –Control (vehicles) –Fadrazol: another aromatase inhibitor –Fadrazol + estrogen Rescue effect? aromatase + E 2 Soma et al, 2000

E 2 receptors found in song system

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

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

Why Neurosteroids?

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