Testosterone

SONG

T is elevated during periods of elevated aggression

T implant increases song rate

control testosterone0.0

2.5

5.0

7.5

10.0

12.5

15.0

treatment

So

ng

s /

10 m

in

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 E2

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

+ E2

Soma et al, 2000

E2 receptors found in song system

Neurosteroid Hypothesis

• Steroid precursors released from adrenal or gonad

• Made into active steroids in the brain

aromataseDHEA

Soma and Wingfield 2001

Effects of DHEA?

aromataseDHEA

HVC volume

Song production

Soma et al, 2002, 2004

Why Neurosteroids?

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