Platelet-activating factor and pain.

Platelet-activating factor (PAF) is a phospholipid mediator that regulates the functions of a variety of cells in the peripheral tissues and in the nervous system. Findings that injection of PAF exogenously at the skin or in the spinal cord induced pain hypersensitivity gave us much attention to its role in pain signaling. Studies using pharmacological and genetic tools to control the functions of the PAF receptor (PAFR) revealed that the PAF/PAFR system plays a role in tissue injury-induced pain, but not in the acute physiological pain evoked by thermal and mechanical stimuli. Recent investigations have focused on the roles of PAFR in pathological chronic pain such as the neuropathic pain that occurs after nerve injury for which there is currently no effective therapy. Nerve injury upregulated PAFRs in dorsal root ganglion (DRG) neurons. Studies using PAFR antagonists and PAFR-deficient mice indicated a crucial role of PAFR in production of tumor necrosis factor α (TNFα) and interleukin-1β (IL-1β) in the DRG and in developing and maintaining neuropathic pain. Thus, blocking PAFRs may be a viable therapeutic strategy for treating neuropathic pain.