Various unc-13 antibodies, including one I designed, did not recognize unc-13 in nerve terminals at the crayfish and Drosophila NMJs. However, syntaxin-1 staining was recognized in nerve terminals in both crayfish and Drosophila. Therefore, I quantified the relative amount of syntaxin-1 between the crayfish phasic and tonic boutons.At neuromuscular junctions (NMJs) of the crayfish leg extensor muscle, I used quantitative immunohistochemistry to determine whether the expression of different exocytotic proteins was different between the phasic and tonic synapses. I tested several proteins, but focused on uncoordinated-13 (unc-13) and syntaxin-1.Normalized data showed that whole phasic boutons contained more syntaxin-1 than whole tonic boutons. However, local syntaxin-1 clusters found within the boutons showed no overall difference in the amount of syntaxin-1 between phasic and tonic boutons. Therefore, the global expression of syntaxin-1 might be associated with synaptic differentiation.