Purpose: Evidence shows that adenosine triphosphate (ATP) is involved in the transmission of multiple chronic pain via P 2 X 7 receptor. This study was to investigate the P 2 X 7 and microglial cells in the chronic prostatitis pain. Materials and Methods: Rats were divided into control group and chronic prostatitis group (n = 24 per group). A chronic prostatitis animal model was established by injecting complete Freund's adjuvant (CFA) to the prostate of rats, and the thermal withdrawal latency (TWL) was detected on days 0, 4, 12 and 24 (n = 6 at each time point in each group). Animals were sacrificed and the pathological examination of the prostate, detection of mRNA expression of P 2 X 7 and ionized calcium binding adaptor molecule 1 (IBA-1) and measurement of content of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the dorsal horn of L 5 -S 2 spinal cord were performed on days 0, 4, 12 and 24. In addition, the content of TNF-α and IL-1β in the dorsal horn of L 5 -S 2 spinal cord was measured after intrathecal injection of inhibitors of microglial cells and/or P 2 X 7 for 5 days. Results: The chronic prostatitis was confirmed by pathological examination. The expression of P 2 X 7 and IBA-1 and the content of TNF-α and IL-1β in rats with chronic prostatitis were significantly higher than those in the control group. On day 4, the expressions of pro-inflammatory cytokines became to increase, reaching a maximal level on day 12 and started to reduce on day 24, but remained higher than that in the control group. Following suppression of microglial cells and P 2 X 7 receptor, the secretion of TNF-α and IL-1β was markedly reduced. Conclusion: In chronic prostatitis pain, the microglial cells and P 2 X 7 receptor are activated resulting in the increased expression of TNF-α and IL-1β in the L 5 -S 2 spinal cord, which might attribute to the maintenance and intensification of pain in chronic prostatitis.
INTRODUCTIONChronic prostatitis, a common urological condition in young and middle-age men, is caused by multiple etiological factors. Pain is a major presentation of chronic prostatitis (1). Previous studies focused on the pathological changes in the prostate, while the pathways related to neurotransmission and the regulatory mechanisms of chronic prostatitis pain have not been studied. Recent studies have identified the chronic prostatitis pain as a visceral referred pain, which is usually accompanied by the dysfunction of pelvic floor muscles. The prostate is innervated largely by the pelvic nerves arising from the L 5 -S 2 spinal cord (2,3).
P2X7 receptor mediates activation of microglial cells in prostate of chemically irritated rats _______________________________________________
277It has also been shown that the transmission and regulation of pain are associated with not only the neurons but the microglia and astrocytes (4,5). Studies also demonstrated that astrocytes and microglias may secrete pro-inflammatory cytokines such as tumor necrosis factors (TNF), interleukin-1 (IL-1), nerve growth fac...