| Vocal communication is an important aspect of social interactions in many species. Effective social interactions require that individuals produce the appropriate vocal signal in a given context, yet relatively little is known about how the brain facilitates context-appropriate communication. The neurotransmitter dopamine is often dysregulated in neurological, developmental, and mental health disorders characterized by communication deficits. Neurotensin is a neuropeptide that strongly interacts with dopamine signaling, and although neurotensin has also been linked to disorders associated with communication deficits, nothing is known about the relationship between neurotensin and vocal communication. This dissertation is focused on investigating the role of neurotensin in vocal signaling across social contexts by using songbirds as a study system. In Chapter 1, neurotensin protein immunolabeling was found to positively relate to sexually-motivated singing behavior in the ventral tegmental area, bed nucleus of the stria terminalis, and lateral septum of male European starlings. In Chapter 2, neurotensin mRNA expression in the song-control nucleus Area X positively related to sexually-motivated song in male starlings. In Chapter 3, mRNA expression of several neurotensin- and dopamine-related genes in the ventral tegmental area, septum, and Area X were shown to positively relate to affiliative song outside of a breeding context in starlings. In Chapter 4, mRNA expression of neurotensin and neurotensin receptor 1 in the song-control system were found to change during development in male zebra fiches. In Chapter 5, neurotensin receptor 1 was shown to co-localize with tyrosine hydroxylase (the rate-limiting enzyme in dopamine synthesis) in the ventral tegmental of male starlings across physiological conditions. The results from these studies are the first to implicate neurotensin in vocal communication and they suggest that interactions between neurotensin and dopamine may underlie the control of context-specific vocalizations. The goal of this work is to reveal basic neurobiological mechanisms for the control of vocalizations that may extend to other species, including humans, and thereby potentially generate novel ideas for the treatment of communication deficits. |
