Figure 6.

Hyperalgesia to mechanical and hypotonic stimuli induced by PGE₂ and 5-HT is TRPC1 and TRPC6 dependent. A, Treatment with TRPC1 or TRPC6 antisense (AS) ODN for 3 d did not affect baseline nociceptive mechanical threshold in control rats (n = 24 for baseline and n = 6 for antisense and mismatch-treated rats; p > 0.05, Tukey's post hoc multiple comparison test). In contrast, the mechanical hyperalgesia induced by PGE₂ and 5-HT was reversed by treatment with TRPC1 or TRPC6 antisense compared with mismatch-treated (MM) rats (n = 18 for baseline and n = 6 for antisense and mismatch-treated rats; *p < 0.001, Tukey's post hoc multiple comparison test). The effect of the antisense was reversible; 4 d after the last ODN injection, the mechanical hyperalgesia induced by PGE₂ and 5-HT was not significantly different from pre-ODN baseline (p > 0.05, Tukey's multiple-comparison test). B, Treatment with TRPC1 or TRPC6 antisense also markedly reduced the number of flinches in response to intradermal injection of hypotonic solution (Hypo) in the presence of PGE₂ and 5-HT compared with mismatch-treated rats (n = 6 for hypotonic solution in presence of PGE₂ plus 5-HT and n = 6 for each ODN group; *p < 0.001, Tukey's post hoc multiple comparison test). C, Paw-withdrawal thresholds were markedly decreased 24 h after thermal injury (118 ± 1 g before vs 74 ± 1 g after thermal injury; n = 36; p < 0.0001, paired Student's t test). Treatment with TRPV4 or TRPC6 antisense for 3 d markedly reversed the mechanical hyperalgesia compared with mismatch ODN-treated rats (n = 6 for all groups). Again, the effect of the antisense treatment was reversible; there was no significant difference in the mechanical thresholds between baseline and ODN-treated groups 4 d after the last ODN injection (n = 36 for baseline and n = 6 for each ODN group; all p > 0.05, Tukey's post hoc multiple comparison test). In contrast, TRPC1 antisense did not affect the mechanical hyperalgesia induced by thermal injury. D, There was a 37 ± 4 and 32 ± 7% decrease in TRPC1 and TRPC6 protein expression level, respectively (n = 3 for all groups; p < 0.05, unpaired Student's t test) in DRG of rats treated with antisense (AS) ODN compared with mismatch ODN-treated rats (MM). The amount of protein loaded in each lane was normalized by probing the membrane with an anti-GAPDH antibody.