The upregulation of EGFR in the dorsal root ganglion contributes to chronic compression of dorsal root ganglions-induced neuropathic pain in rats.

The epidermal growth factor receptor (EGFR) located in dorsal root ganglion has been found as a new target for chronic pain treatment. However, it is not clear whether the change of EGFR expression in the dorsal root ganglion contributes to neuropathic pain development. In this study, we used a chronic compression of unilateral lumbar dorsal root ganglions (CCD)-induced rat neuropathic pain model and found that CCD caused the upregulation of both phosphorylated EGFR and total EGFR expression in compressed lumbar 4/5 (L4/L5) dorsal root ganglions by western blotting and immunohistochemistry methods. Either inhibition of EGFR activation by EGFR inhibitor or knockdown of EGFR expression by EGFR small interference RNA (siRNA) relieved CCD-induced pain hypersensitivities to mechanical, thermal, and cold stimuli in rats. Moreover, EGFR knockdown reversed CCD-induced the increase of intracellular mammalian target of rapamycin (mTOR) expression as well as the activation of the satellite glial cells in the ipsilateral compressed L4/L5 dorsal root ganglions. These findings suggest that not only activated EGFR but also total EGFR contribute to CCD-induced neuropathic pain by enhancing intracellular mTOR signaling.