VAMP in phasic and tonic axonal terminals is susceptible only to BoNT/B-LC under low frequency stimulation.

<p>Immunostaining of VAMP and synapsin after the injection of inactive and active TeNT-LC (<i>A</i>), BoNT/D-LC (<i>B</i>) and BoNT/B-LC (<i>C</i>) into the phasic or tonic axon during the low frequency stimulation experiments. In <i>A-C</i>, arrows denote phasic terminals and arrow heads denote tonic terminals. The yellow areas in the merged image represent an overlap of VAMP and synapsin immunoreactivity. In <i>C</i>, the injected boutons contain only synapsin indicating that active BoNT/B-LC cleaved VAMP under low frequency stimulation. Note that only active BoNT/B-LC reduced VAMP immunoreactivity under low frequency stimulation conditions. In <i>B</i>,<i>C</i>, no tonic terminals were present in the phasic image with active neurotoxin. Scale bars – <i>A</i> and <i>B</i>: 19 µm; <i>C</i>: 10 µm.