Figure 5.

HPA-axis activity in different rat strains after SNI. (A) Excretion of Fecal Corticosterone Metabolites (FCM)—AUC. The full time-course is presented in Supplementary Fig. S4. FCM was measured at baseline, 1, 2, 4 and 6 months post-surgery. AUC was calculated for each individual/cage. Note that this parameter is recorded on cage-level, not subject-level, and N = 5 for SNI-groups, N = 4 for Sham groups. Two-way ANOVA showed significant effects of strain with Bonferroni’s post testing showed that both the SD—(P < 0.05–0.001) and WKY-strain (P < 0.01–0.001) had significantly higher FCM-levels than F344/Ico, F344/Du and LEW, as detected pairwise combined for the two surgical groups for each strain. (B) Weight of adrenal glands. (C) Weights of pituitary gland for each animal. Notice that the adrenal and pituitary weights presented in panels (B,C) are potentially affected by the size of the animal, explaining why the statistical analysis was performed with body weight as a covariate. The analysis showed significant effect of strain (two-way ANCOVA, strain*surgery, covariate = body weight) for both organs, and Bonferroni’s post hoc test detected differences between strains. For adrenal weights; SD had significantly higher adrenal weight than F344/Du (P < 0.05) and WKY (P < 0.001), and WKY also having smaller adrenal weights than F344/Ico (P < 0.01) and LEW (P < 0.001), when body weight was included as a covariate. For pituitary, SD had significantly higher weight/size than WKY (P < 0.05) and LEW (P < 0.001), and F344/Ico had higher pituitary weights than LEW (P < 0.001). Given the lack of statistical effect of surgery or strain*surgery interaction, the post hoc differences are presented overall between strains, and not divided for the surgical groups. Data are presented as scatter plot and lines indicating mean ± S.E.M.