This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacodynamics, Subject name: Pharmacology
[{'content': 'Botulinum toxin acts by: \nSelect and explain. \nA. Presynaptic release of acetyl choline, B. Presynaptic inhibition of release of acetylcholine, C. GABA mimetic, D. GABA antagonist', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans.(b) Presynaptic inhibition of release of acetylcholineRef Katzung 10th ed. Ch 27* Botulinum toxin is a neuromascular blocking agent which act at neuromascular junction by blocking the presynaptic release of Ach vesicles.* Doing so, it reduces spasticity in a variety of neurologic conditions (ie, spasmolytics).* NOTE: Neuromuscular blocking drugs interfere with transmission at the neuromuscular end plate and lack central nervous system activity. Also KnowMOA of drugs and their siteDrugSite of ActionMoaLocal anestheticsNerve axonsBlock Na channelsHemicho- liniumAt cholinergic nerve terminalBlocks uptake of choline and slows synthesisVesamicolCholinergic terminal vesiclePrevents storage, depletesReserpineAdrenergic terminal vesiclePrevents storage, depletesTyramine, Ampheta- mineAdrenergic nerve terminalsPromote transmitter releaseBethanecholReceptors, parasympathetic effector cells (smooth muscle, glands)Binds and activates muscarinic receptorsAtropineReceptors, parasympathetic effector cellsBinds muscarinic receptors; prevents activatio', 'role': 'assistant'}]