Figure 13.

Proteasome inhibitor does not affect type II priming. A, Rats were treated with intradermal injection of the proteasome inhibitor MG-132 (1 μg) on the dorsum of the hindpaw. Thirty minutes later, repeated (hourly, ×4) injections of DAMGO (1 μg) were performed at the same site and the mechanical nociceptive threshold was evaluated 30 min after the fourth administration. Significant mechanical hyperalgesia was observed after the fourth injection of DAMGO in the group pretreated with MG-132 compared with baseline (**p = 0.0069, paired Student's t test). B, A different group of rats was treated with intradermal injection of MG-132 (1 μg) and, after 30 min, repeated (hourly, ×3) injections of DAMGO (1 μg) were performed at the same site. One hour after the third injection of DAMGO, PGE₂ (100 ng) was injected and mechanical hyperalgesia was evaluated 30 min and 4 h later. Two-way repeated-measures ANOVA followed by Bonferroni post hoc test showed no difference between the groups in PGE₂-induced mechanical hyperalgesia (F_(1,8) = 1.04; p > 0.05, when comparing both groups; NS, p = 0.3658), indicating that the proteasome system does not play a role in the prolongation of the hyperalgesia induced by PGE₂ observed in type II priming. n = 6 paws per group.