University of Texas at Austin
University of Texas: Dopamine
Using dopamine as an example, the page gives a description of how neurotransmitters work and the effects of drugs and enzymes on neurotransmitter function.
US National Library of Medicine
Medline Plus: Parkinson's Disease
From MedlinePlus, a video tutorial featuring information on Parkinson's Disease with accompanying text. Includes closed captioning option. [0:24]