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Seasonal changes in the densities of α 2 ‐noradrenergic receptors are inversely related to changes in testosterone and the volumes of song control nuclei in male European starlings
Author(s) -
Riters Lauren V.,
Eens Marcel,
Pinxten Rianne,
Ball Gregory F.
Publication year - 2002
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.10131
Subject(s) - biology , receptor , seasonal breeder , endocrinology , medicine , context (archaeology) , dominance (genetics) , adrenergic receptor , testosterone (patch) , zoology , paleontology , biochemistry , gene
The functions of song and the contextual cues that elicit song change seasonally in parallel with testosterone (T) concentrations in male European starlings. T is high in spring when at least one function of male song is that of immediate mate attraction, and low outside the context of breeding, when starlings primarily use song for dominance or flock maintenance. Several brain nuclei that control song contain high densities of α 2 ‐adrenergic receptors. T can regulate the density of α 2 ‐adrenergic receptors in the avian brain, indicating that the density of α 2 ‐adrenergic receptors within the song system might change seasonally. Although the function of seasonal brain variation is not entirely clear, in many songbirds the volumes of song nuclei are largest when T is high and males sing most. Male starlings, however, sing both when T is high and when T is low. Therefore, exploring seasonal changes in T and the volumes of song nuclei could provide insight into the function of these changes. The present study was performed to explore the relationships among T, the volumes of song nuclei, and the densities of α 2 ‐adrenergic receptors within the song system of male starlings. Song nuclei (the high vocal center [HVc], robust nucleus of the archistriatum [RA], and Area X) were largest, T was highest, and the density of α 2 ‐adrenergic receptors (within HVc and RA) was lowest during the breeding season. The reverse pattern was observed outside of the breeding season. These results suggest that changes in T, volumes of song nuclei, and α 2 ‐receptor densities might regulate seasonal changes in song behavior or the context that will elicit song in male starlings. J. Comp. Neurol. 444:63–74, 2002. © 2002 Wiley‐Liss, Inc.