Botulinum toxin blocks neuromuscular transmission by which of the following mechanism:: (A) Closure of Ca++ channels at presynaptic membrane, (B) Closure of Na+ channels at the postsynaptic membrane, (C) Opening of K+channels at the presynaptic membrane, (D) Opening of Cl– channels at the postsynaptic membrane
Answer is A. Botulinum toxin acts by inhibiting the calcium mediated exocytosis of ACh from the vesicles in the synapse.