The distribution of androgen receptors was studied in the brain of the Japanese quail (Coturnix japonica), the zebra finch (Taeniopygia guttata), and the canary (Serinus canaria) by immunocytochemistry with a polyclonal antibody (AR32) raised in rabbit against a synthetic peptide corresponding to a sequence located at the N-terminus of the androgen receptor molecule. In quail, androgen receptor-immunoreactive cells were observed in the nucleus intercollicularis and in various nuclei of the preoptic-hypothalamic complex, namely, the nucleus preopticus medialis, the ventral part of the nucleus anterior medialis hypothalami, the nucleus paraventricularis magnocellularis, the nucleus ventromedialis hypothalami, and the tuberal hypothalamus. In the two songbird species, labeled cells were also observed in various nuclei in the preoptic-hypothalamic region, in the nucleus taeniae, and in the nucleus intercollicularis. Additional androgen receptor-immunoreactive cells were present in the androgen-sensitive telencephalic nuclei that are part of the song control system. These immunoreactive cells filled and outlined the boundaries of the hyperstriatum ventrale, pars caudalis, nucleus magnocellularis neostriatalis anterioris (both in the lateral and medial subdivisions), and nucleus robustus archistriatalis. The immunoreactive material was primarily present in cell nuclei but a low level of immunoreactivity was also clearly detected in cytoplasm in some brain areas. These studies demonstrate, for the first time, that androgen receptors can be detected by immunocytochemistry in the avian brain and the results are in general agreement with the binding data obtained by autoradiography with tritiated dihydrotestosterone. Immunocytochemical methods offer several advantages over autoradiography and their use for the study of the androgen receptor will greatly facilitate the analysis of steroid-sensitive systems in the avian brain.

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