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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