This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
[{'content': 'All are cholinergic drugs except \nSelect and explain. \nA. Memantine, B. Tacrine, C. Rivastigmine, D. Donepezil', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Memantine acts on NMDA receptors .remaining all the drugs are indirectly acting cholinergicn drugs used in the treatment of alzhimers disease. Ref: KDT 6th ed pg 472,473', 'role': 'assistant'}]