Gonadal steroid receptor mRNA in catecholaminergic nuclei of the canary brainstem

Steroid actions in the song system may be modulated by ascending inputs fro m catecholaminergic (CA) brain nuclei; however, whether these nuclei contai n steroid receptors is unknown. Here, we compared the distribution of andro gen receptor (AR) and estrogen receptor-alpha (ER-alpha) mRNA with that of tyrosine hydroxylase immunoreactivity (TH-IR) in the brainstems of male can aries. Areas containing AR and ER-alpha mRNA overlapped with areas containi ng TH-IR cell bodies in the locus ceruleus and the area ventralis of Tsai. The substantia nigra and the midbrain central gray contained both TH-IR and AR mRNA. The presence of AR and ER-alpha within CA cell groups suggests th at sex steroid hormones may modulate song production at the site of CA synt hesis. (C) 2001 Published by Elsevier Science Ireland Ltd.