Figure 3
Inhibition of glial cells attenuates the hyperalgesic phenotype in SS rats. (a): Naïve SD (left image), BN (center image) and SS (right image) rats had their PAG collected and prepared for immunohistochemistry. Sections were stained with the glial cell activation marker Iba. Quantification of the staining (b) showed significant difference in active glial cells across the strains (F(2,6) = 6.883, *p = 0.0280), with higher intensity in sections from SS rats compared to SD (p = 0.0277) and BN (p = 0.0326) sections (one-way ANOVA followed by Bonferroni posttest). (c): SD (open circles), BN (gray circles) and SS (closed circles) rats received an i.p. injection of the glial cell inhibitor minocycline (30 mg/kg). Evaluation of the mechanical nociceptive thresholds, by the Randall-Selitto test, was performed on the dorsum of the hindpaw (left panel) or on the gastrocnemius muscle (right panel), before and 24 h after the injections. We observed a significant difference in the minocycline effect across the groups (F(2,29) = 152.4 for the hindpaw; F(2,29) = 367.8 for the gastrocnemius, p < 0.0001 for both when the three groups were compared, two-way repeated measures ANOVA followed by Bonferroni posttest), with increase in the nociceptive threshold in the SS rats (hindpaw: ****p < 0.0001; gastrocnemius: ***p = 0.0001), but no significant change in the SD (hindpaw: p = 0.3042; gastrocnemius: p > 0.9999, NS) or BN (hindpaw: p > 0.9999; gastrocnemius: p = 0.2395, NS) groups. Together, these findings suggest a role for glial cells in the SS rat hyperalgesic phenotype. (c): SS, n = 8; SD, n = 12; BN, n = 12.
