Oluwemimo Adeyanju
Dopamine Transmission in Tourette's Syndrome
Mentor:  Dr. Kevin Black, Department of Psychiatry, Washington University School of Medicine

Irregularities found in dopamine transmission in the basal ganglia particularly the nucleus accumbens (NA) might be the cause of Tourette syndrome. Tourette syndrome (TS) is a neuropsychiatric disorder that affects about one out of every 200 people. It is defined by chronic tics involving movement and vocalizations. Several studies have revealed that there is an abnormality in the striatal dopaminergic innervation in TS patients. Additionally, antagonist drugs that impede dopamine D2 receptors and agonist drugs that produces the same effects as dopamine both are used to reduce tic severity, which further supports this hypothesis. We endeavored to determine to what extent dopaminergic innervation in TS patients differs from that in tic-free control subjects using positron emission tomography (PET), levodopa, and [11C]raclopride (*rac). The change in *rac binding in the NA induced by administration of levodopa is computed in several steps. First, an NA region is traced on a magnetic resonance image (MRI) of each subject's brain by comparison to a published histological atlas. Second, a validated, reliable method aligns the PET and MR images. Third, the NA region and the PET data are used to compute NA binding potential in each condition for each subject. I will discuss NA anatomy, the practical difficulty associated with its identification on available MRI data, and preliminary information on the reliability of tracing in this data set