Central vasotocin-immunoreactive system in a male passerine bird (Junco hyemalis)

Previous investigations have identified regions of the avian brain that con tain immunoreactive vasatocinergic (VT-ir) cell bodies and fibers. These st udies exclusively used domesticated species, and the relevance of the findi ngs for free-living birds has not been established. The present study used immunocytochemistry to determine the neuroanatomical distribution of the VT -ir system in the brain of a well-studied male passerine bird (dark-eyed ju nco, Junco hyemalis) obtained from a natural population in interior Alaska (65 degrees N, 147 degrees W). VT-ir cell bodies were observed in several b rain regions (paraventricular and supraoptic nuclei, nucleus of the stria t erminalis), where they have been described in other oscine species. VT-ir f ibers were widespread in many brain regions and were especially abundant in the medial preoptic nucleus, the basal region of the septum, and the hypot halamic-neurohypophyseal tract. Fibers were also present in brain regions t hat are involved in the control of vocal behavior including the ventromedia l capsular region of the nucleus robustus archistriatalis and the dorsomedi al portion of the mesencephalic nucleus intercollicularis. The widespread b rain distribution of VT-ir cell bodies and fibers in juncos generally resem bles that of domestic birds and suggests a role for this neuropeptide in th e control of reproductive behavior and physiology. (C) 1999 Wiley-Liss, Inc .