Aggressive interactions rapidly increase androgen synthesis in the brain during the non-breeding season

• Published in: Hormones and behavior Vol. 57; no. 4; pp. 381 - 389
• Main Authors: Pradhan, Devaleena S., Newman, Amy E.M., Wacker, Douglas W., Wingfield, John C., Schlinger, Barney A., Soma, Kiran K.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.04.2010; Elsevier; Elsevier BV
• Subjects: 3-Hydroxysteroid Dehydrogenases - biosynthesis; 3-Hydroxysteroid Dehydrogenases - genetics; 3beta-HSD; Aggression; Aggression - physiology; Aggressiveness; Androgens; Androgens - biosynthesis; Androstenedione; Animal communication; Animals; Aromatase; Behavioral psychophysiology; Biological and medical sciences; Biosynthesis; Birds; Brain; Brain Chemistry - drug effects; Brain Chemistry - physiology; Challenge hypothesis; Chromatography, High Pressure Liquid; Coenzyme; Cofactor; Dehydroepiandrosterone - blood; DHEA; Enzymes; Estradiol; Estrogens; Fundamental and applied biological sciences. Psychology; Hormones and behavior; Intracrine; Male; Melospiza melodia; NAD; NAD - pharmacology; Neurology; Neurosteroid; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Seasons; Sexual Behavior, Animal - physiology; Social Environment; Song sparrow; Songbird; Sparrows - physiology; Testis - metabolism; Testosterone; Testosterone - blood; DHEA; Aggression; Intracrine; 3beta-HSD; Estrogens; Neurosteroid; Cofactor; Estradiol; Songbird; Coenzyme; NAD; Testosterone; Aromatase; Challenge hypothesis; Song sparrow; Androstenedione; Sound production; Central nervous system; Estrogen; Estrogen synthase; Encephalon; Song; Testicular hormone; Season; Androgen; Enzyme; Interaction; Ovarian hormone; Dehydroepiandrosterone; Sex steroid hormone; Aggressiveness
• ISSN: 0018-506X; 1095-6867; 1095-6867
• DOI: 10.1016/j.yhbeh.2010.01.008

In male song sparrows ( Melospiza melodia), territorial challenges during the breeding season can rapidly increase circulating levels of testosterone (T). During the non-breeding season, male song sparrows are highly aggressive, but the gonads are regressed and plasma T levels are non-detectable and unaffected by territorial challenges. The pro-hormone dehydroepiandrosterone (DHEA) is elevated in song sparrow plasma and brain during the non-breeding season and may be locally converted to sex steroids in the brain to regulate aggression. The enzyme 3β-hydroxysteroid dehydrogenase/Δ5-Δ4 isomerase (3β-HSD) converts DHEA to androstenedione (AE) using the cofactor NAD +, and this is a critical rate-limiting step. We predicted that brain 3β-HSD activity varies seasonally and is rapidly modulated by aggressive challenges. In the first study, brain 3β-HSD activity was highest in the non-breeding season in specific regions. In the second study, a simulated territorial challenge rapidly increased aggressive behavior in non-breeding song sparrows. Brain 3β-HSD activity, when measured without exogenous NAD +, increased by ∼ 250 to 500% in telencephalic regions of challenged subjects. When brain 3β-HSD activity was measured with exogenous NAD +, these effects of territorial challenges were not observed. These data suggest that territorial challenges rapidly increase endogenous NAD + levels or increase 3β-HSD activity specifically within a NAD-rich subcellular compartment. Together, these two studies suggest a shift from systemic to local sex steroid signaling in the non-breeding season. Local steroid signaling produces high spatial and temporal specificity of steroid signals and avoids the costs of high systemic T levels during the non-breeding season.