Investigating Vocal Deficits in Songbirds with Neurotoxin Induced Dopamine Depletion in the Basal Ganglia
Dopamine (DA) input from the midbrain modulates the activity of basal ganglia circuitry important for motor learning and control in a variety of taxa. DA loss is associated with movement disorders in humans. In songbirds, DA is important for motivational behavior underlying reproductive drive. Within the zebra finch species, DA modulates social-context dependent behavior when the bird is vocally practicing alone versus performing to a potential female mate. During these singing behaviors, there are differences in DA levels within Area X, the specialized sub-region of the zebra finch basal ganglia dedicated to song learning and ongoing adult song maintenance. These natural differences in DA levels are associated with quantifiable changes in features of song, suggesting that the songbird may be a suitable model for investigating DA-driven changes in voice associated with early stages of Parkinson's Disease. In the present study, I used Western blotting to characterize natural changes in protein biomarkers of DA, such as tyrosine hydroxylase, across non-singing and singing behaviors. In a separate group of birds, I injected the neurotoxin 6-hydroxydopamine (6-OHDA) into Area X and assessed the effects of DA depletion on these biomarkers and on features of song in different behavioral contexts. With 6-OHDA administration, measurable decreases in DA biomarkers were detected, and select acoustic features of song became more stereotyped. Ongoing investigations will determine how this DA loss impacts receptor-mediated changes in the underlying neural circuitry.