Figure 4.

Adeno-associated viral IL-10 attenuates established CCI-induced mechanical allodynia. After predrug (baseline; BL) assessment on the von Frey test, sham (Panels A, B) or CCI (Panels C, D) surgery was performed (timing denoted by the first vertical dotted line). Behavioral assessments were reassessed Days 3 and 10 after surgery to document the lack of allodynia in sham operated rats and development of bilateral allodynia in CCI groups. ANOVA revealed reliable main effects of CCI (F _1,40 = 197.446, p < 0.0001) and laterality (F _1,40 = 6.356, p < 0.05). After the Day 10 assessment, rats received intrathecal (i.t.) injections of either AAV2-GFP (Control) or AAV2-r-IL-10 (timing denoted by the second vertical dotted line). Behavioral assessments were again recorded on Days 13, 15, 17, 19, 21, 24, 26, and 30 after surgery; that is, Days 3, 5, 7, 9, 11, 14, 16, and 20 days after AAV. While neither AAV2-GFP nor AAV2-r-IL-10 exerted marked effects in sham operated animals (Panels A, B), AAV2-r-IL-10 transiently attenuated bilateral CCI allodynia compared to CCI operated AAV2-GFP treated animals (Panels C, D). For Days 13–26, ANOVA revealed reliable main effects of CCI (F _1,40 = 496.336, p < 0.0001), IL-10 (F _1,40 = 59.636, p < 0.0001), and laterality (F _1,40 = 28.565, p < 0.0001), and interactions between CCI and IL-10 (F _1,40 = 72.988, p < 0.0001) and CCI and laterality (F _1,40 = 9.325, p < 0.01). At Day 30, behavioral responses were not significantly different from Day 10 preinjection levels (F _1,40 = 0.696, p > 0.40).