Experimental Study On The Cellular Immune Function Of Intrathecal Morphine And Its Mechanism In Rats

Objective: The experiment was performed to study the effects of intrathecal morphine on cellular immune function , neuroendocrine and to investigate its mechanism .Methods: One day before experiment, Sprague-Dawley rats were inserted polyethylene catheters (PE-10) into spinal subarachnoid space. Serum corticosterone was measured by EIA using an EIA kit and PHA-induced splenic lymphocytes proliferation was measured by MTT. 1 .To evaluate the effects of intrathecal morphine on cellular immune function and neuroendocrine. The rats were randomly divided into two group: normal saline(NS) group , morphine group. 2.To investigate the mechanism of the immunosuppression by morphine. Rats were randomly divided into four groups this time: morphine group , naloxone group , naloxone antagonization group and pretreatment of RU486 (i.p) Group. At the time of experiment, naloxone antagonization group were pretreated with naloxone 140g/rat, 5 minutes later morphine (40g/50l) was injected in intrathecal .The pretreatment of RU486 group, was pretreated with RU486 (i.p), 30 minutes later, morphine was inject (i.t). 6 hours later, blood samples were taken to assay the serum corticosteron level and all rats were sacrificed and the splenocytes were harvested to assess the proliferation capacity.Results: 1 .PHA-induced splenic lymphocyte proliferation was significantly suppressed and the serum corticosterone level had elevated after morphine (40g/50l) injected in intrathecal. 2. The effects could be partially antagonize by 140g of naloxone (i.t). 3. The pretreatment with RU486 intraperitoneally had no effect on suppression of PHA-induced splenic lymphocyte proliferation produced by morphine.Conclusion: intrathecal morphine suppressed PHA-induced splenic lymphocyte proliferation and stimulated the hypothalamic-pituitary-adrenal axis. The effects of morphine were mainly by central opioid receptor and could be blocked by naloxone-an opioid receptor antagonist. The immunosuppression produced by morphine is independent of activation of the hypothalamic-pituitary-adrenal axis.