Developmental pattern of CB1 cannabinoid receptor immunoreactivity in brain regions important to zebra finch (Taeniopygia guttata) song learning and control.

Zebra finches learn song during distinct developmental stages, making them an important species for studying mechanisms underlying vocal development. Distinct interconnected forebrain regions have been identified as important to specific features of zebra finch vocal learning and production. Because prior experiments have demonstrated that late postnatal exposure to cannabinoid agonists alters zebra finch song learning, we have sought to identify brain regions likely involved in it. By using an affinity-purified polyclonal antibody directed against the zebra finch CB(1) cannabinoid receptor, we have studied staining patterns in groups of males at 25, 50, 75, and >100 days of age (adults). A general waxing and waning of staining intensity were observed over this developmental period. Distinct staining of song-related brain regions was also noted. Early establishment of staining patterns within rostral telencephalic song regions [area X and lateral magnocellular nucleus of the anterior nidopallium (lMAN)] suggests a role in auditory learning. Later establishment and maintenance in adulthood of small somata and neuropil staining within regions of rostral telencephalon [HVC and robust nucleus of the arcopallium (RA)] are consistent with a vocal motor role for cannabinoid signaling. Our results provide insight into brain regions likely responsible for cannabinoid-altered vocal learning and add to accumulating evidence supporting an important role for cannabinoid signaling in CNS development.