The role of endogenous opioid peptides in the antinociceptive effect of 15-deoxyΔ12,14-prostaglandin J2 in the temporomandibular joint

We have previously demonstrated that peripheral administration of 15d-PGJ(2) in the Temporomandibular joint (TMJ) of rats can prevent nociceptor sensitization, mediated by peroxisome proliferator activated receptor-gamma (PPAR-gamma), and kappa- and delta- opioid receptors. However, the mechanism that underlies the signaling of PPAR-gamma (upon activation by 15d-PGJ(2)) to induce antinociception, and how the opioid receptors are activated via 15d-PGJ(2) are not fully understood. This study demonstrates that peripheral antinociceptive effect of 15d-PGJ(2) is mediated by PPAR-gamma expressed in the inflammatory cells of TMJ tissues. Once activated by 15d-PGJ(2), PPAR-gamma induces the release of beta-endorphin and dynorphin, which activates kappa- and delta-opioid receptors in primary sensory neurons to induce the antinociceptive effect. (C) 2016 Elsevier Ltd. All rights reserved.