Temporal expression of cytokines and their receptors mRNAs in a neuropathic pain model.

Proinflammatory mediators, such as tumor necrosis factor (TNF) alpha, interleukin (IL)-1beta and IL-6 have been found to play a key role in the propagation of persistent pain states. We investigated the temporal expressions of the mRNAs and the receptor mRNAs of TNFalpha, IL-1beta and IL-6 in rat dorsal root ganglia and spinal cord in a chronic constriction injury model of neuropathic pain. Our results show that the maximal induction of IL-6 mRNA occurred later and was more sustained than those of TNFalpha and IL-1beta mRNAs in the dorsal root ganglia and spinal cord following chronic injury. Receptors mRNAs, except TNF receptor 2 and gp130 mRNAs, showed temporal profiles that were similar to those of their cytokine mRNAs. Additionally, the induction of the mRNAs of cytokines and of their receptors in the dorsal root ganglia was more rapid than in the spinal cord.