This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Organic mental disorders, Subject name: Psychiatry
[{'content': "Biochemical aetiology of Alzheimer's disease relates to \nSelect and explain. \nA. Serotonin, B. Dopamine, C. Acetylcholine, D. GABA", 'role': 'user'}, {'content': "Answer: C \nExplanation: Alzheimer's disease is the commonest cause of dementia and it is not treatable disorder. Neurochemically there is a marked decrease in the brain choline acetyltransferase (CAT) with a similar decrease in brain acetylcholinesterase(AchE) (Ref: a sho textbook of psychiatry, Niraj Ahuja, 7th edition, pg no.24). The main neurotransmitter implicated in Alzheimer's disease is Acetylcholine.", 'role': 'assistant'}]