Androgen receptor location in the dark-eyed junco using a probe for in situ hybridization histochemistry generated from zebra finch cDNA.

Due to the role of sex steroids, namely testosterone (T), in the development and production of song in songbirds, androgen receptor (AR) densities in the brain regions controlling this behavior (i.e., the song control system) have long been studied. Many methods have been used to determine AR density and location to investigate the functional role of T in song development and production; however, a riboprobe developed from zebra finch (Taeniopygia guttata) cDNA was shown to be much more sensitive than previous methods. The zebra finch is a common model for song development and is sexually dimorphic, but does not breed seasonally or display seasonal changes in song control region volume. In this study, we used this riboprobe for in situ hybridization histochemistry (ISHH) to describe AR mRNA location in the brain of the dark-eyed junco (Junco hyemalis), a seasonally breeding model for which T has been shown to be important. Additionally, we provide a detailed comparison of AR mRNA location between these species. We found that this probe is indeed highly sensitive. We detected AR mRNA in four major regions of the song control system (HVC, MAN, RA and Area X). Additionally, we found that the location of AR mRNA in other regions varied only slightly between these two species. These findings suggest that this method is suitable for use across songbirds and it could be useful in the ongoing attempts to elucidate the roles of sex steroid hormones on the development of this and other sex steroid dependent behaviors in songbirds.