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