TNF and Pain: Microglia can cause chronic neuropathic pain through the release of various cytokines and chemokines associated with the transmission of pain signals and also decreased microglial activity may prevent the development of chronic neuropathic pain [11]. On the other hand, it was observed that increased proinflammatory gene expression, such as tumor necrosis factor alpha (TNF-α) and IL-6, was returned to baseline values following PRF therapy [12].