Diltiazem promotes DRG axon outgrowth. A, Diltiazem concentration-response for DRG axon outgrowth on CSPG. Diltiazem (25 μM) increases the total axon length per neuron by 2.0-fold. B, No effect of diltiazem (5 μM) on DRG axon length is detected on laminin. C, βIII-tubulin immunostaining of DRG neurons cultured on CSPG for 24 hours in the presence of diltiazem (25 μM) or vehicle. Data are mean ± S.E. n = 12-36. Scale bar, 100 μm. *, p < 0.05; ****, p < 0.0001, one-way ANOVA, post hoc Dunnett; NS, not significant, Student’s two-tailed t-test.