Distribution of synaptic antigens at NMJs in control (a–d) and N-CAM^−/−(e–h) mice. Cross-sections of hindlimb muscles were doubly stained with antibodies to N-CAM (a, e), synaptophysin (b, f), erbB3 (c, g), or agrin (d, h) plus rhodamine–α-bungarotoxin (a′–h′). Mutant end plates were devoid of N-CAM, as expected, but did not otherwise differ from controls. Scale bar, 10 μm.