Nerve injury induces long-lasting pathological pain, namely neuropathic pain (NP), which is dysfunction of the whole pain transmission process, including dorsal root ganglia (DRG) in peripheral nerve system (PNS). Melatonin is well known over a long period of time as hormone of circadian rhythm closely related with the various aspects of pain conditions. Melatonin and melatonin related receptors (MTR1A and MTR1B) exerted amazing analgesic effect in many acute and chronic pain experimental studies, including electrically induced pain, thermally induced pain, mechanical induction of pain and chemical induction of pain. However, the anti-nociceptive action of melatonin in NP is still controversial and unclear. In the present study, our research firstly demonstrated the expression of melatonin receptors in the DRGs, and what more interesting is that MTR1A and MTR1B have a completely different cell type location (MTR1A in the satellite cells and MTR1B in the neurons). In order to get a basic glance at the effects of melatonin and MTR1B on the DRG neurons, a microarray analysis is applied to screen the pain related different expression genes in the primary DRGs cultured neurons with treatment of 1mM melatonin, 100渭M MTR1B agonist 8-M-PDOT or vehicle (1% ethanol of normal saline). Subsequent examination was performed, and the finding suggested that melatonin suppressed neuropathic pain via MTR1B dependent and independent pathways in dorsal root ganglia neurons. And MTR1B in DRG may be a potential therapeutic target for NP.

RORα, NOS1, TNF-1α, IL-1β