MAPPING THE NEURAL CIRCUITRY OF THE VENTRAL PALLIDUM
Cindy Barrientos, Byungkook Lim.
University of California, San Diego, La Jolla, CA.
Neuropsychiatric disorders in the United States are estimated to cost over $300 billion annually. Despite their cost and prevalence, there are significant gaps in our knowledge about the neural mechanisms that lead to these disorders. There are specialized neural circuits in the brain that underlie rewarding and aversive behavior. Changes to these systems may lead to neuropsychiatric illnesses, such as depression or addiction. In this study, we examine the neural circuitry of the ventral pallidum (VP), a region that anatomical and behavioral studies suggest is important in mood disorders, yet remains under studied. We approached this problem in multiple ways. First, we used retrograde tracing on wild-type mice to examine VP connections. Next, we used genetically modified mice to determine the inputs and outputs of 2 prominent neuronal VP subtypes: the parvalbumin (PV) expressing neurons and the choline acetyltransferase (ChAT) expressing neurons. Different connectivity of these distinct populations may suggest differential roles of the 2 types of cells in neuropsychiatric illness. Our results indicate that PV-expressing neurons project onto regions such as the ventral tegmental area, the lateral habenula, the lateral hypothalamus, and the mediodorsal nucleus of thalamus. The ChAT-expressing neurons, however, only have strong projections to the basolateral amygdala and central amygdala. Many of these locations receiving inputs from the VP also send reciprocal projections back to the VP. Determining these neural systems of reward represent early steps in discovering the mechanisms of neuropsychiatric disorders, providing the foundation for future studies to develop more effective treatments and better prevention strategies for mood disorders.