Dopamine Receptor Imaging to Predict Response to Stimulant Therapy in Chronic TBI

Summary

Deficits in memory, attention, cognitive, and executive functions are the most common disabilities after traumatic brain injury (TBI). Dopamine (DA) neurotransmission is implicated in these neural functions and dopaminergic pathways are recognized to be frequently disrupted after TBI. One of the most widely used DAergic drugs is methylphenidate (Ritalin®). Methylphenidate increases synaptic DA levels by binding to presynaptic dopamine transporters (DAT) and blocking re-uptake. PET with methylphenidate challenge to measure tonic DA release provides valuable insight into the molecular basis of attention-deficit hyperactivity disorder (ADHD) and addiction, as well as practical information regarding likely effectiveness of therapy (1). The objectives of this study are to use PET imaging with \[11C\]-raclopride, a D2/D3 receptor ligand, before and after administering methylphenidate, to measure endogenous DA release in patients who are experiencing problems with cognition, attention and executive function in the chronic stage after TBI. In addition, we will use TMS to test short intracortical inhibition, a gamma-aminobutyric acid receptor A (GABAA) - mediated phenomenon, which is under partial DA control, as a measure of dopaminergic activity on and off methylphenidate.

Timeline

Start

2014-09

Primary completion

2018-08

Completion

2018-08

Publications

• Background Volkow ND, Wang GJ, Tomasi D, Kollins SH, Wigal TL, Newcorn JH, Telang FW, Fowler JS, Logan J, Wong CT, Swanson JM. Methylphenidate-elicited dopamine increases in ventral striatum are associated with long-term symptom improvement in adults with attention deficit hyperactivity disorder. J Neurosci. 2012 Jan 18;32(3):841-9. doi: 10.1523/JNEUROSCI.4461-11.2012.
• Background Whyte J, Hart T, Vaccaro M, Grieb-Neff P, Risser A, Polansky M, Coslett HB. Effects of methylphenidate on attention deficits after traumatic brain injury: a multidimensional, randomized, controlled trial. Am J Phys Med Rehabil. 2004 Jun;83(6):401-20. doi: 10.1097/01.phm.0000128789.75375.d3.

Drugs

Indications