Evidence that dopamine within motivation and song control brain regions regulates birdsong context-dependently

Vocal communication is critical for successful social interactions among conspecifics, but little is known about how the brain regulates context-appropriate communication. The neurotransmitter dopamine (DA) is involved in modulating highly motivated, goal-directed behaviors (including sexually motivated singing behavior), and emerging data suggest that the role of DA in vocal communication may differ depending on the context in which it occurs. To address this possibility, relationships between immunolabeled tyrosine hydroxylase (TH, the rate-limiting enzyme in catecholamine synthesis) and song produced within versus outside of a breeding context were explored in male European starlings (Sturnus vulgaris). Immunocytochemistry for dopamine beta-hydroxylase (DBH; the enzyme that converts DA to norepinephrine) was also performed to provide insight into whether relationships between song and TH immunoreactivity reflected dopaminergic or noradrenergic neurotransmission. Measures of TH and DBH were quantified in song control regions (HVC, Area X, robust nucleus of the acropallium) and regions implicated in motivation (medial preoptic nucleus (POM), ventral tegmental area (VTA), and midbrain central gray). In Area X, POM, and VTA measures of TH correlated with song produced within, but not outside of a breeding context. DBH in these regions did not correlate with song in either context. Together, these data suggest DA in both song control and motivation brain regions may be more tightly linked to the regulation of highly goal-directed, sexually motivated vocal behavior.