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Deprecated: Implicit conversion from float 209.6 to int loses precision in C:\Inetpub\vhosts\kidney.de\httpdocs\pget.php on line 534 Brain+Behav+Evol 2015 ; 86 (2): 110-21 Nephropedia Template TP
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Testosterone mediates seasonal growth of the song control nuclei in a tropical bird #MMPMID26346733
Small TW; Brenowitz EA; Wojtenek W; Moore IT
Brain Behav Evol 2015[]; 86 (2): 110-21 PMID26346733show ga
In mid- to high-latitude songbirds seasonal reproduction is stimulated by increasing daylength accompanied by elevated plasma sex steroid levels, increased singing, and growth of the song control nuclei (SCN). Plasticity of the SCN and song behavior are primarily mediated by testosterone (T) and its metabolites in most species studied thus far. However, the majority of bird species are tropical and have less pronounced seasonal reproductive cycles. We have previously documented that equatorial rufous-collared sparrows (Zonotrichia capensis) exhibit seasonal neuroplasticity in the SCN. Manipulating T in these birds, however, did not alter singing behavior. In the current study we investigated whether T mediates plasticity of the SCN in a similar manner to temperate songbirds. In the first experiment we treated captive male birds with T or blank implants during the non-breeding season. In a second experiment we treated captive males with either blank implants, T-filled implants, T with Flutamide (FLU; an androgen receptor antagonist) or T with FLU and 1,4,6-androstatriene-3,17-dione (ATD; an estrogen synthesis inhibitor) during the breeding season. In both experiments, the volumes of brain areas HVC, Area X, and RA were measured along with singing behavior. In summary, T stimulated growth of HVC and RA and the combined effect of FLU and ATD reversed this effect in HVC. Area X was not affected by testosterone treatment in either experiment. Neither T-treated birds nor controls sang in captivity during either experiment. Together these data indicate that T mediates seasonal changes in the HVC and RA of both tropical and higher latitude bird species even if the environmental signals differ. However, unlike most higher latitude songbirds, we found no evidence that motivation to sing or growth of Area X are stimulated by T under captive conditions.