Figure 9.

Age‐related changes in growth associated protein 43 (GAP‐43) and agrin expression in in neuromuscular junctions (NMJs) of hindlimb muscles. Changes in (A) GAP‐43‐immunoreactivity (IR) and (E) agrin‐IR (in arbitrary units [a.u.]) in NMJs of old tibialis anterior (TA), soleus (Sol), extensor digitorum longus (EDL), and gracilis (Gra) muscles expressed as the percentage of increase compared with adult respective muscles. Representative confocal images of NMJs of TA and Gra muscles from young, adult, and old mice immunostained for (B1–D3) GAP‐43 and (F1–H3) agrin, both in green; muscle sections were also stained with α‐bungarotoxin (α‐Bgtx) (red) for endplate identification. Data in the graphs are expressed as the mean ± SEM, ^* P < 0.05; ^*** P < 0.001, and ^**** P < 0.0001 vs. adult muscles (one‐way ANOVA and post hoc Bonferroni's test); one muscle for each muscle type taken from four adult and five old mice was used for analysis; 80–100 NMJs per muscle type were examined. Scale bars: In (D3) = 10 μm [valid for (B1–D2)] and in (H3) = 10 μm [valid for (F1–H2)].