Parkinson's disease treatment. Artwork of Parkinson's disease nerve cells (neurones) being treated with the drug Levodopa (L-dopa). The neurones, with dark blue nuclei and long nerve processes, are in the basal ganglia nerve clusters in the centre of the brain. In the neurones are Lewy bodies (red) which are believed to cause them to degenerate. This results in a lack of the neurotransmitter dopamine, and the muscle tremors and rigid posture of Parkinson's disease sufferers such as the elderly man seen in silhouette. Here, L-dopa (L-dihydroxyphenylalanine) is being converted into dopamine (orange balls) as it moves into the brain from a blood vessel (bottom right).