An amino acid that functions as an inhibitory neurotrans-mitter in the brain. GABA reduces the sensitivity of muscle cells to nerve stimulation, decreasing muscle movement. It appears that the amount of GABA present in the brain decreases in Parkinson’s disease, particularly in the subthalamic nucleus (STN), possibly contributing to symptoms such as TREMORS, RESTLESS LEG SYNDROME, and LEVODOPA-induced dyskinesia and dystonia. The drug baclofen (common brand name Lioresal), a GABA agonist taken to relieve these symptoms, binds with GABA receptors and mimics the action of GABA. However, there is also some evidence that GABA functions to an extent as a dopamine antagonist, blocking the effect of this neurotransmitter, which is already depleted in Parkinson’s. The result would be worsening of symptoms such as bradykinEsia. Research continues to explore the role of GABA and other amino acids in movement DISORDERS.