Brain Aromatase and Territorial Aggression Across the Seasons in Male Song Sparrows

Sarah A. Heimovics, H. Bobby Fokidis and Kiran K. Soma

in Brain Aromatase, Estrogens, and Behavior

Published in print October 2012 | ISBN: 9780199841196
Published online January 2013 | e-ISBN: 9780199979837 | DOI:

Series: Oxford Series in Behavioral Neuroendocrinology

Brain Aromatase and Territorial Aggression Across the Seasons in Male Song Sparrows

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Research on free-living songbirds has revealed novel and important insights into the various contexts in which 17β-estradiol (E2) activates aggressive behavior. In the Pacific Northwest, male song sparrows defend territories during the breeding season (when circulating testosterone levels are elevated) and during the nonbreeding season (when circulating testosterone levels are nondetectable). The ecological context of territorial aggression differs greatly across seasons, but several lines of evidence indicate that both breeding and nonbreeding aggression depend on the conversion of testosterone into E2 by aromatase. Remarkably, there appears to be a seasonal shift in the source of androgen substrate for brain aromatase: from a systemic source (the testes) in the breeding season to a local source (the brain itself) in the nonbreeding season. This seasonal shift may have evolved to reduce the exposure of peripheral tissues and other brain areas to the deleterious effects of testosterone and E2.

Keywords: dehydroepiandrosterone; DHEA; estradiol; estrogens; intracrine; neurosteroid; songbird; 3β-HSD; territory; testosterone

Chapter.  7781 words.  Illustrated.

Subjects: Neuroscience

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