The central goal of this study is to investigate the functional and physical interplay between the dopamine (DA) D2 autoreceptor (D2R) and the dopamine transporter (DAT) and the role of this interplay in the regulation of DA neurotransmission. DA neurons are functionally heterogeneous with spatially separated somatodendritic and axonal projections initiating in two neighboring brain structures; ventral tegmental area (VTA) and substantia nigra (SN). Aberrations in DA neurotransmission are implicated in neuropsychiatric disorders; including schizophrenia, attention deficit/hyperactivity disorder (ADHD), drug addiction, and Parkinson's disease. Critical mechanisms in the regulation of DA availability at the synapse include the activation of D2 autoreceptors and DA uptake via DAT. Traditionally, these two mechanisms ? D2R and DAT- have been studied individually; however, exciting new evidence from in vitro experiments suggests that D2 autoreceptor and DAT interact physically and possibly functionally. Published data and our own preliminary findings support the hypothesis that D2 autoreceptor and DAT exist as a macromolecular complex and that D2 autoreceptor activation regulates DAT activity and trafficking in DA neurons through a GIRK-mediated mechanism. To address this hypothesis we will use a multidisciplinary approach combining molecular, biochemical, electrophysiological, and optic approaches in cultured DA neurons and brain slices containing somatodendritic regions of VTA, SNc and their projection areas (dorsal striatum and nucleus accumbens) where both DAT and D2R are co- expressed.
In aim 1, we will use genetic, electrophysiological and optic tools to examine functionally whether D2R activation increases DAT activity and trafficking through a mechanism involving GIRK-mediated hyperpolarizarion of the cell membrane.
In aim 2, we will use molecular, biochemical, and optic tools to examine the contribution of the D2R-DAT physical interaction to the D2R-mediated regulation of DAT activity and trafficking. We will compare and contrast findings obtained from SN and VTA, projections areas in the dorsal striatum vs nucleus accumbens, as well as samples from male and female animals. Given the role of D2R and DAT as therapeutic targets for DA-related conditions, the successful completion of this work will reveal the physiological significance of the interplay between presynaptic D2 receptor and DAT. The result of this work will have wide-ranging significance, as it will reveal a unique mechanism for the FDA approved D2R agonists' and DAT antagonists' regulation of dopamine neurotransmission.
Dopamine neurotransmission is implicated in drug addition, neurological and neuropsychiatric disorders. This project examines the functional interplay between D2 autoreceptor and DAT in dopamine neurons, and will determine whether D2 activation affect the strength of DAT/D2R interaction. The result of this work will have wide-ranging significance, as it will reveal a unique mechanism for the FDA approved D2R agonists' and DAT antagonists' regulation of dopamine neurotransmission.