This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
[{'content': "In which of the following diseases decrease in levels of single neurotransmitter was first identified? \nSelect and explain. \nA. Alzheimer's disease, B. Parkinson's disease, C. Huntington disease, D. Schizophrenia", 'role': 'user'}, {'content': "Answer: B \nExplanation: Neurons of the substantia nigra communicate with neurons of the basal ganglia by liberating the neurotransmitter dopamine (DA). In Parkinson's disease, neurons of the substantia nigra progressively degeneration; as a result, the amount of DA available for neurotransmission in the corpus striatum is lowered. Ref Harrison20th edition pg 2456", 'role': 'assistant'}]