FIGURE 5.

Effect of glucose and lactic acid on DRG neurons. Cultured DRG neurons were treated with glucose (25 mm), lactic acid (10 mm), or recombinant mouse TNF-α protein (rmTNF-α; 100 ng/ml) for 24 h. The expression of Pdk2 and Pdk4 (A) and Trpv1 and Asic3 (B) mRNAs was assessed by real-time RT-PCR. Cultured DRG neurons were treated with 25 mm glucose for 24–48 h (C) or with 1, 6, 10, and 15 mm lactic acid for 24 h (D). An MTT assay (left) or trypan blue staining (right) were performed to assess the neuronal viability at the specified time points following the treatment. For trypan blue staining, the number of neurons in the whole image was counted. The average number of neurons in control conditions was 400.33 ± 6.23. The experiment was done in duplicate. E, H&E staining of paraffin sections of the DRG was performed to assess diabetes-induced alterations in the DRG tissue integrity at 3 weeks post-STZ injection. Quantification of vacuolated DRG neurons (in percent) is presented in the adjacent graph. Scale bar, 50 μm. *, p < 0.05 versus the untreated controls; #, p < 0.05 between the indicated groups, one-way ANOVA with Dunnett's multiple-comparison test (for A, B, and D); two-way ANOVA (for C). NS, not significant; n = 3 (for A–D) or n = 6 (for E); mean ± S.E. (error bars).