Melatolin Enhanced The Immune Fuction In Intrathecal Pumping Morphine Caused Immunosuppressed Rats

As a centrally opiods analgesic, morphine was used extensively in treating on postoperative pain,inflammatory pain,chronic neuropathic pain and cancer pain.Considerable data suggest that opiods may negatively influence immune competency in pain-free subjects by skin or abdominal system administration.Some scholars have founded that melatonin may ameliorate celluar immunity and humoral immunity.Objective To evaluate the effect of melatolin on immune function in intrathecal pumping morphine caused immunosuppressed ratsMethods 32 Sprague-Dawley rats (280±30g) were randomly divided into 4 groups(n=8 in each group):saline group(NS), morphine group (M,10μg/h), morphine plus saline group (M+NS) and morphine plus melatolin group (M+MLT),Which were anesthetized with 10% Chlroral Hydrate 300～350mg/kg. A microspinal catheter(inner diameter 0.12mm,outer diameter 0.35mm)was inserted into the lumbar subarachnoid space(8cm). and after five days,an ALZET(?) osmotic minipump was connected tightly with a polyurethane catheter whose inner dimeter is about o.36mm. Melatonin (5mg/kg) was intraperitoneally injected for 7 days.Spleens were aseptically removed to obtain splenic cells. T lymphocyte function was evaluated based on Concanavalin-A(ConA) induced splenocyte proliferation. A modified lactic acid dehydrogenase release assay to assess NK cell activity. And phenotypic expression of cell surface markers of T lymphocyte subsets (CD3+,CD3+CD4,CD3+CD8+,CD4+/CD8+) and NK cell(CD161+) in the spleen were analyzed by flow cytometry.Result compare to NS group, after pumping morphine 7 days, spleen indexes and splenocyte proliferation induced by ConA and NK cell activity were significantly suppressed by intrathecal pumping morphine; Phenotypic expression of T lymphocyte subsets and NK cell assessed by flow cytometry were different from control group in all morphine group. The results showed that 5mg/kg (ip) melatonin was able to recover the lowered splenocyte proliferation, NK cell activity and T lymphocyte subsets and NK cell phenotype in immunosupressed rats.Conclusion (1) Intrathecal pumping morphine inhibited lymphocyte proliferation and NK cell activity, decreased splenic lymphocyte numbers, and altered phenotypic expression of cell surface markers dose-dependently. (2)MLT can recover NK cell activity, lymphocyte proliferative capatity and phenotypic expression of T lymphocyte subsets and NK cell, but the mechanism deserve further investigation.