TY - JOUR
T1 - Photoperiodic condition modulates the effects of testosterone on song control nuclei volumes in male European starlings
AU - Bernard, Daniel J.
AU - Ball, Gregory F.
N1 - Funding Information:
Joe Casto, Tom Hahn, and Randy Nelson provided comments on an earlier version of the paper. We thank Ilsa Rucosky for her technical assistance. The research was support by grants from the NSF (IBN920893 and IBN9514525) to G.F.B.
PY - 1997/2
Y1 - 1997/2
N2 - Songbirds possess a specialized network of brain nuclei mediating song learning and production, the song system. In many species, the nuclei in this circuit are larger in volume in males housed on long photoperiods than in males housed on short photoperiods. Exposure to long days initially leads to increases in circulating levels of testosterone (T) and it is generally believed that volume changes in the song system are controlled by T- dependent effects of photoperiod. However, a growing body of evidence indicates that photoperiod can also have T-independent effects on song system morphology. Previous work in our laboratory suggested that photoperiodic condition may modulate the effects of exogenous testosterone on the volumes of song control nuclei in male European starlings (Sturnus vulgaris). In the present report, we tested the hypothesis that photorefractoriness attenuates the effects of T on the volumes of song control nuclei in starlings. One group of long-day photorefractory males (16L:8D) was exposed to exogenous T and two groups of short-day photosensitive birds (8L: 16D) were either implanted with T or blank (control) capsules. After 8 weeks, T levels were elevated in both groups of T-implanted birds and were undetectable in control animals. Volumes of the high vocal center were larger in T-implanted photosensitive birds than in both T-implanted photorefractory and control photosensitive males, which did not differ. These results suggest that photorefractoriness renders the song nuclei of starlings less sensitive to stimulatory effects of T. Plasticity in the starling song system appears to require the coordination of the appropriate hormonal milieu with a permissive photoperiodic condition.
AB - Songbirds possess a specialized network of brain nuclei mediating song learning and production, the song system. In many species, the nuclei in this circuit are larger in volume in males housed on long photoperiods than in males housed on short photoperiods. Exposure to long days initially leads to increases in circulating levels of testosterone (T) and it is generally believed that volume changes in the song system are controlled by T- dependent effects of photoperiod. However, a growing body of evidence indicates that photoperiod can also have T-independent effects on song system morphology. Previous work in our laboratory suggested that photoperiodic condition may modulate the effects of exogenous testosterone on the volumes of song control nuclei in male European starlings (Sturnus vulgaris). In the present report, we tested the hypothesis that photorefractoriness attenuates the effects of T on the volumes of song control nuclei in starlings. One group of long-day photorefractory males (16L:8D) was exposed to exogenous T and two groups of short-day photosensitive birds (8L: 16D) were either implanted with T or blank (control) capsules. After 8 weeks, T levels were elevated in both groups of T-implanted birds and were undetectable in control animals. Volumes of the high vocal center were larger in T-implanted photosensitive birds than in both T-implanted photorefractory and control photosensitive males, which did not differ. These results suggest that photorefractoriness renders the song nuclei of starlings less sensitive to stimulatory effects of T. Plasticity in the starling song system appears to require the coordination of the appropriate hormonal milieu with a permissive photoperiodic condition.
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U2 - 10.1006/gcen.1996.6829
DO - 10.1006/gcen.1996.6829
M3 - Article
C2 - 9038260
AN - SCOPUS:0031081018
SN - 0016-6480
VL - 105
SP - 276
EP - 283
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
IS - 2
ER -