Figure 3

Response properties of mechanically sensitive, thermally insensitive (CM) and polymodal (CPM) C-fibers after P14 inflammation. A: No changes were observed in the mechanical thresholds of CPM neurons at any time point after inflammation of the hairy skin at P14. B: No differences in heat threshold in the CPM fibers were detected after P14 inflammation. C: However, there was an increase in the mean peak instantaneous frequencies to mechanical stimulation of the skin in the CPM neurons one day after P14 inflammation. This effect was transient as firing returned to naïve levels by the three day time point. D: Similar results were found in terms of the mean peak instantaneous frequencies to heat stimuli in the CPM fibers. However, the enhanced firing to heat was maintained at the three day time point and resolved by day seven. E: Although there was not a statistically significant reduction in mechanical thresholds in the CM neurons, there was a trend towards reduced mechanical thresholds in these afferents one day after injection of carrageenan into the hairy skin at P14. F: The CM fibers however did display increased mean peak instantaneous frequencies to mechanical stimulation of the skin one day after P14 inflammation. *p value <0.05; ^#p value < 0.1, mean ± SEM; One-way ANOVA with Tukey’s post hoc test for thresholds and Kruskal-Wallis with Dunn’s post hoc tests for mean peak instantaneous frequencies. See text for animal and afferent numbers.