Synaptotagmin II immunoreactivity in normal and botulinum type-A treated mouse motor nerve terminals.

The distribution of synaptotagmin II, a synaptic vesicle protein, was examined by immunohistochemistry at normal mouse motor nerve terminals and after botulinum type-A treatment. An immunoreactivity to synaptotagmin II was detected in both control and botulinum type-A treated motor nerve terminals including newly formed sprouts. These data, together with other reports showing the absence of synaptotagmin I at the neuromuscular junction, suggest that synaptotagmin II is the isoform involved in transmitter release at motor nerve terminals.