GDNF hyperalgesia is mediated by PLCγ, MAPK/ERK, PI3K, CDK5 and Src family kinase signaling and dependent on the IB4‐binding protein versican

Abstract

The function of the isolectin B4 (IB4⁺)-binding and GDNF-dependent Ret (Ret⁺)-expressing non-peptidergic subpopulation of nociceptors remain poorly understood. We demonstrate that acute administration of GDNF sensitizes nociceptors and produces mechanical hyperalgesia in the rat. Intrathecal IB4–saporin, a selective toxin for IB4⁺/Ret⁺-nociceptors, attenuates GDNF but not NGF hyperalgesia. Conversely, intrathecal antisense to Trk A attenuated NGF but not GDNF hyperalgesia. Intrathecal administration of antisense oligodeoxynucleotides targeting mRNA for versican, the molecule that renders the Ret-expressing nociceptors IB4-positive (+), also attenuated GDNF but not NGF hyperalgesia, as did ADAMTS-4, a matrix metalloprotease known to degrade versican. Finally, inhibitors for all five signaling pathways known to be activated by GDNF at GFRα1/Ret: PLCγ, CDK5, PI3K, MAPK/ERK and Src family kinases, attenuated GDNF hyperalgesia. Our results demonstrate a role of the non-peptidergic nociceptors in pain produced by the neurotrophin GDNF and suggest that the IB4-binding protein versican functions in the expression of this phenotype.