Reduced expression of Epac2 attenuates PGE₂-induced augmentation of capsaicin-evoked iCGRP release in sensory neurons grown in NGF, but has no effect in neurons grown without added NGF.

<p>A and B: Columns are the mean ± SEM of iCGRP release as % of total peptide content/well/10 min from sensory neurons grown without added NGF (A) or in the presence of 30 ng/ml NGF (B). Wells of cells (n = 9 from a minimum of 3 separate harvests) were exposed for 10 min to HEPES alone (Basal; open columns), or HEPES in the presence of 30 nM capsaicin (CAP; shaded columns) in the absence or presence of 1 µM PGE₂ as indicated by the horizontal bars. Release experiments were performed in cultures exposed to 200 nM scramble siRNA, siRNA to Epac1, or siRNA to Epac2 as indicated. An asterisk indicates a significant difference from basal release, whereas a cross indicates a significant difference in capsaicin-stimulated release in the presence of PGE₂ compared to vehicle control using analysis of variance with Tukey's post hoc test. C: The top portion shows a representative Western blots of Epac1 and actin from cultures grown without added NGF or with 30 ng/ml NGF as indicated and treated with 200 nM scramble siRNA (SCsiRNA), Epac1siRNA, or Epac2siRNA as indicated. In the lower portion, each column represents the mean ± SEM of the effects of exposure to SCsiRNA, Epac1siRNA or Epac2siRNA on Epac1 expression from 3 experiments. An asterisk indicates a statistically significant decrease in Epac expression using ANOVA and Tukey's post hoc test. D: The top portion shows a representative Western blots of Epac2 and actin from cultures grown without added NGF or with 30 ng/ml NGF as indicated and treated with 200 nM scramble siRNA (SCsiRNA), Epac1siRNA, or Epac2siRNA as indicated. In the lower portion, each column represents the mean ± SEM of the effects of exposure to SCsiRNA, Epac1siRNA or Epac2siRNA on Epac2 expression from 3 experiments. An asterisk indicates a statistically significant decrease in Epac expression using ANOVA and Tukey's post hoc test.