Figure 4.

Age-related changes in α-motor axons parallel those found in sensory afferents. Analysis of α-motor axons (YFP) innervating the postsynaptic site on extrafusal muscle fibers, visualized by using fluorescently tagged α-bungarotoxin (BTX). In the same muscles used to examine sensory afferents, fewer α-motor axons were found fully innervating postsynaptic sites in older mice (A–D). At least three animals per age group and at least 50 NMJs per muscle were analyzed. Scale bar = 20 µm. Error bar = STE. *p < .05, **p < .01, ***p < .001.