Fig. 4.

Capsaicin causes fragmentation and reduced motility of axonal mitochondria. a–f Capsaicin- and DMSO-treated axons were transfected with Mito-Dendra2 (Mito), examined by time-lapse imaging, and then stained with PGP9.5 antibodies. Compared to DMSO-treated nerves (b, c, arrowheads), axonal swellings (d, arrows) increased and mitochondria became shorter in capsaicin-treated cultures (e, f, arrowheads). g ₁, g ₂ Mean mitochondrial length in DRG axons was significantly reduced after capsaicin treatment. When axons were sub-grouped according to their mean mitochondrial length, the proportion of axons with mean mitochondrial length <1 μm was increased upon capsaicin treatment (***P = 0.0001 by Mann–Whitney test. χ ² = 34.07, P < 0.0001 by chi-square test). h–j Representative frames of time-lapse images of axonal mitochondrial transport and resulting kymographs before and 1 h (1 h) after DMSO or capsaicin treatment. The length (arrows) and motility (arrowheads) of mitochondria were maintained after DMSO but were decreased after capsaicin treatment (***P < 0.0001 by Kruskal–Wallis test and Dunn’s multiple comparison test). The numbers of axons are shown in the bar graphs. Scale bars a–f 10 μm; h 5 μm