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
Biochemical aetiology of Alzheimer's disease relates to 
Select and explain. 
A. Serotonin, B. Dopamine, C. Acetylcholine, D. GABA
C: Acetylcholine
Answer: C: Acetylcholine 
Explanation: 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.