A. Schematic representation of LPS muscle (in blue) and its innervation by the superior division of the oculomotor nerve (sdCNIII). B–E. YFP-expressing motor nerve terminals (green) were imaged in P5 (B), P7 (C), P11 (D) and P21 (E) LPS muscles isolated from thy1:yfp line H mice. AChR clusters were simultaneously visualized by labeling with fluorescently conjugated bungarotoxin (BTX; magenta). At all ages, YFP-containing motor nerve terminals were observed that failed to innervate entire postsynaptic sites, indicating these synapses were multiply innervated. Arrowheads highlight AChR-rich regions of the postsynaptic membrane unoccupied by YFP-labeled nerve terminals. Scale bar = 50μm. F. Numbers of NMJs multiple innervated synapses in P5, P7, P11, P14 and P21 LPS muscles isolated from thy1:yfp line H mice. Each black dot represents the percentage of YFP-labeled NMJs that were multiply innervated from a single LPS muscle. N = number of LPS muscles analyzed per age. n = total of number of NMJs analyzed per age.