Fig. 5.

Voltage-gated Na⁺ channels (Na-Ch) are aggregated at extrasynaptic regions by expression of neural chick agrin. Antisera specific for Na⁺ channels specifically labeled endplates (A, B). Preabsorption with immunogenic peptide (C) inhibits the staining at endplates (D). The distribution of Na⁺ channel immunoreactivity is shown for two extrasynaptic sites of muscle fibers injected with agrin expression plasmids (E, F, G–I). The general outline of Na⁺ channel immunoreactivity (E, arrows) follows ectopic AChR aggregates (F, arrows). In some cases, however, the distribution of Na⁺ channels (G, arrow) was not confined to the site of extrasynaptic AChRs (H) induced by agrin (I). Scale bars: in A–F, 35 μm; in G–I, 50 μm.