Fig. 6: FDA-approved small molecules glycopyrrolate and mexiletine increase the intrinsic growth capacity of axotomized dorsal root ganglion (DRG) neurons, and promote in vivo axon regeneration after sciatic nerve crush injury.

a, b Primary DRG cultures were prepared from adult male C57BL/6 mice, and treated with top-ranked small molecules at various concentrations. DMSO (0.1%) was used as solvent control. Glycopyrrolate and mexiletine induced maximal neurite outgrowth of DRG neurons, when compared with solvent controls. Cell survival assay was performed by WST-1 cell survival assay. All tested small molecules did not exhibit any adverse cell survival effect on DRG neurons. Scale bar: 500 µm. Mean ± SEM of triplicates. c Schematic diagram illustrating the experimental paradigm for sciatic nerve pinch test. We performed nerve pinch test in adult mice injected intraperitoneally with glycopyrrolate (2 mg/kg) or mexiletine (10 mg/kg) for 3 consecutive days after injury. d, e Both glycopyrrolate (d) and mexiletine (e) markedly accelerated in vivo axon regeneration after sciatic nerve crush injury as assessed by sciatic nerve pinch tests. The most distal axonal regrowth in mice treated with glycopyrrolate and mexiletine was increased significantly by 61 and 59%, respectively. The number of GAP43-positive regenerating axons were increased by 73% in glycopyrrolate-treated mice and 67% in mexiletine-treated mice. Scale bar: 100 µm. Mean ± SEM (n = 5–6 per group); *P < 0.05; one-way ANOVA followed by post hoc Bonferroni test in (b); Student’s t test in (d, e).