title: Sex steroid-independent effects of photostimulation on the song-control system of white-throated sparrows (Zonotrichia albicollis).
abstract: Brain nuclei within the song-control system of songbirds are seasonally plastic during adulthood. These nuclei are larger in birds exposed to long, spring-like days than short, winter-like days. There is overwhelming evidence that this effect is mediated by testosterone (T). However, castration studies have also demonstrated that photostimulation has gonad-independent effects on song-control system plasticity, but these studies rarely control for extra-gonadal sources of T. In this study, we used anti-androgen and anti-estrogen treatments in combination with castration to determine the sex steroid-independent effects of photostimulation on HVC size and doublecortin immunoreactivity in white-throated sparrows (Zonotrichia albicollis). Birds were kept on short days or photostimulated for 1 month. Photostimulated birds were intact, castrated and treated with anti-androgens and anti-estrogens, or castrated and treated with T. HVC volumes of photostimulated birds were significantly larger than short-day birds. HVC volume of castrated birds given anti-androgens/-estrogens was significantly larger than short-day birds, indicating a sex steroid-independent effect of photostimulation. Similar results were observed for RA. The number of migrating neurons (immunoreactive for doublecortin) in HVC did not differ between treatment groups. Our data support the view that photostimulation alone can drive song-control system nuclei growth, and that concurrent exposure to T potentiates this growth. Moreover, these effects do not appear dependent on modulation of neuron migration.
authors.affiliation: Department of Psychology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A 5C2, Canada.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Robertson
authors.affiliation: Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A 5B7, Canada.
authors.forename: Michael R
authors.initials: MR
authors.lastname: Hasstedt
authors.affiliation: Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A 5B7, Canada.
authors.forename: Caitlin L
authors.initials: CL
authors.lastname: Vandermeer
authors.affiliation: Department of Psychology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A 5C2, Canada; Department of Biology, Advanced Facility for Avian Research, University of Western Ontario, London, ON N6A 5B7, Canada. Electronic address: smacdou2@uwo.ca.
authors.forename: Scott A
authors.initials: SA
authors.lastname: MacDougall-Shackleton
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects; D002369:Castration; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D007124:Immunoenzyme Techniques; D008297:Male; D055495:Neurogenesis / Q000187:drug effects; D010775:Photic Stimulation; D012621:Seasons; D012725:Sexual Behavior / Q000187:drug effects; D046370:Sparrows / Q000502:physiology*; D013739:Testosterone / Q000494:pharmacology*; D014828:Vocalization, Animal / Q000187:drug effects* / Q000502:physiology
chemical_list: D004967:Estrogens; D013739:Testosterone
keywords: Birdsong; Doublecortin; Gonadal steroids; Photoperiod; Song-control nuclei; Songbird