Studies On The Analgesic Effect Of Polysaccharopeptide And Its Mechanism

Objective: To study the analgesic effect of polysaccharopeptide(PSP)and discuss the mechanism of this analgesia. Methods: The tail stimulation-vocalization test and hot-plate test were used to observe the analgesic effect of PSP. Intracerebroventricular(icv)injection of interleukin-2 recepeor(IL-2R) α McAb or naloxone was performed to examine the effect on the analgesic effect of PSP. The IL-2 and IL-2R expression in mediobasal hypothalamus(MBH) was studied immunohistochemically. Nitric oxide(NO) and nitric oxide synthase(NOS) were measured in plasma as well as in brain. Results: After intragastric (ig) administration of different (high,medium and low)doses of PSP for 6 days,the pain threshold was increased significantly and a dose-effect relationship was observed.The analgesic effect of PSP was blocked by icv injection of IL-2R α McAb,but not by naloxone. PSP could increased the NO content in plasma and in brain, as well as the NOS content in the brain. After PSP administration the IL-2 expression in MBH was increased, while the IL-2R expression in MBH was decreased.Conclusion: PSP has a definite analgesic effect and its analgesic site is in the MBH.The analgesia might be produced by the binding with the IL-2R in MBH by IL-2 secreted by T cells after PSP and entered into the brain. The analgesic effect of PSP might also be mediated by the NO induced by IL-2.