Chronic pain is a major clinical problem, yet the mechanisms underlying the transition from acute to chronic pain remain poorly understood. In mice, reduced expression of GPCR kinase 2 (GRK2) in nociceptors promotes cAMP signaling to the guanine nucleotide exchange factor EPAC1 and prolongs the PGE2-induced increase in pain sensitivity (hyperalgesia). Here we hypothesized that reduction of GRK2 or increased EPAC1 in dorsal root ganglion (DRG) neurons would promote the transition to chronic pain. We used 2 mouse models of hyperalgesic priming in which the transition from acute to chronic PGE2-induced hyperalgesia occurs. Hyperalgesic priming with carrageenan induced a sustained decrease in nociceptor GRK2, whereas priming with the PKCε agonist ΨεRACK increased DRG EPAC1. When either GRK2 was increased in vivo by viral-based gene transfer or EPAC1 was decreased in vivo, as was the case for mice heterozygous for
Huijing Wang, Cobi J. Heijnen, Cindy T.J. van Velthoven, Hanneke L.D.M. Willemen, Yoshihiro Ishikawa, Xinna Zhang, Anil K. Sood, Anne Vroon, Niels Eijkelkamp, Annemieke Kavelaars
EPAC1 level in DRG after carrageenan- and ΨεRACK-induced priming.