Pharmacology General 64c80ac8 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 High-Yield Explanation Botulinum toxin acts by inhibiting the calcium mediated exocytosis of ACh from the vesicles in the synapse.