Figure 3.

AChE distribution in the PC of a mouse sternomastoid endplate. (A) Paradigm for the measurement of the distribution of gold-labeled AChE sites in the PC. Distances from the axonal pre-synaptic membrane (0.0) of each gold particle (orange arrow), and of the boundaries of the BL on both sides of the particle (green and blue arrows), were measured and divided by the width of the PC at that site (yellow dashed line); Bar, 0.1 μm. (B) Cumulative display of the gold-labeled AChE sites (measured in A) in a normalized PC of mouse sternomastoid endplate (five mice, 28 NMJs). Most gold particles are found on the synaptic BL (blue and green lines connect the BL border measurements on either side) in the PC between the presynaptic axonal membrane (0.0) and the postsynaptic muscle membrane (1.0). (C) Quantitative distribution of the gold-labeled AChE sites across the width of the PC, from compiled data obtained as in (A,B). Presynaptic axonal membrane, at X = 0.0, postsynaptic muscle membrane at X = 1.0. The histogram of the gold-particles (orange, upper panel) relative to the histograms of the BL boundaries (green-blue, lower panel) shows that the AChE sites are mainly spread over the BL in the PC. It should be noted that the AChE sites are predominantly closer to the postsynaptic muscle membrane than to the presynaptic nerve membrane. *, see text in “Results” section for detailed statistical parameters.