Botulinum toxin binds to receptors present at the axon terminal in order to enter the neuron. what vesicular transport process do you think is involved in the toxin entering the neuron

In the  toxin entering the neuron  while the botulinum toxin binding to the receptor the processes Endocytosis and exocytosis are involved. 
Both endocytosis and exocytosis are cell processes of bulk transport used to move macromolecules such as proteins or polysaccharides into or out of the cell.
By the endcytosis process materials are imported into the cell.
In exocytosis, materials are exported out of the cell via secretory vesicles