TNF and peripheral nerve injury: TNFα signaling in uninjured DRG neurons mediates the activation of voltage-gated sodium channels (Nav) in a dose-dependent manner by upregulating current densities of tetrodotoxin (TTX)-sensitive and TTX-resistant Nav 1.3 and Nav 1.8 in the neurons via p38 MAPK cascade following peripheral nerve injury [36, 39, 40].