MMP-2/-9 expression after CFA injection and the effect of MMP-9 inhibition on CFA-induced mechanical allodynia. (A, B) Levels of MMP-9 and MMP-2 mRNA in the ipsilateral DRG (A) and DHSC, (B) after CFA or vehicle (sham) injection (*P < 0.05, **P < 0.01 CFA versus corresponding sham, n = 4). (C, D) Dexamethasone (DEXA, 2 mg/kg i.p) or vehicle (saline) were daily administered for 4 consecutive days to sham or CFA rats, starting from day 9 after CFA or saline injection into the paw. Transcript levels were quantified by RT-qPCR. Values were normalized to rat S26 mRNA levels and reported to the control group sham/saline set at 1 (dotted line). The data represent the mean ± SEM of 4 rats per group (*P < 0.05, **P < 0.01 CFA/saline versus CFA/DEXA). (E) MMP-9 inhibitor (MMP-9i, 5 μg) or vehicle (10% DMSO) were intrathecally (i.t) injected daily for 4 consecutive days starting from day 9 after CFA injection. The paw withdrawal threshold (g) was evaluated using the von Frey test. Data represent the mean ± SEM of six rats per group (**P < 0.01 MMP-9i- versus vehicle-treated rats).