In songbirds, song is regulated by a specialized group of brain nuclei known as the song system. Other aspects of courtship, such as male sexual interest in a female, are likely regulated by the medial preoptic nucleus (POM). The song control system and the POM are rich in norepinephrine, which appears to regulate courtship behaviors, including song. Zebra finches (Taeniopygia guttata) exhibit an extreme sexual dimorphism in song behavior; males sing, primarily to attract or maintain mates, and females do not. We explored possible sex differences in the distribution and density of the α2-adrenergic receptors in the song system and POM of zebra finches. Receptors were labeled with the selective ligand, [3H] RX821002, via autoradiographic procedures. In males, dense α2-receptors were observed in the song system (Area X, the high vocal center (HVc), the lateral portion of the magnocellular nucleus of the anterior neostriatum, and the robust nucleus of the archistriatum). In contrast, in females neither the lateral portion of the magnocellular nucleus of the anterior neostriatum nor the HVc could be identified based on α2-receptor binding. Females lack Area X and indeed differential α2-binding was not observed within the female lobus parolfactorius. The robust nucleus of the archistriatum contained less dense α2-binding in females compared to males. Alpha2-binding in the POM was similar in males and females. The dimorphism in α2-binding in nuclei of the song system likely relates to the dimorphism in song behavior observed in male and female zebra finches.
- Sex differences
- [H] RX821002
ASJC Scopus subject areas
- Cellular and Molecular Neuroscience