IRF8 and myocardial infarction: To test whether macrophage inhibition could rescue these effects in vivo, we administered minocycline (20 mg/kg/day in drinking water), a known macrophage deactivator.35–38 Minocycline reduced IRF8 expression in T1–T4 DRGs by ~76% in 4-week post-MI rats, restoring levels to those of sham controls (Figure 6A, B).