Effect Of Intrathecal PSD-93 AS ODN On Morphine Toleranced CCI Rats

Background Neuropathic pain is a series of pain syndrome originated by the injury or disease of central or peripheral nervous system. Neuropathic pain originated by the injury of peripheral nerve presents hyperpathia, allodynia, spontaneous pain and so on. The pathogenesy of neuropathic pain is not clear , and there isn't effective therapy by now. Among all the drugs, morphine is the most typical one.As an effective narcotic analgesic, morphine is used for various kinds of acute and chronic pain, but its serviceable range is greatly confined by its addiction and toleration.Referring to various neurotransmitter system and signal transduction system, the mechanism of morphine tolerance is very complicated. In recent years, the participation of NMDA-receptor in the morphine tolerance has been proposed.As one kind of the membrane-bound guanylate kinase (MAGUK) , PSD-93 can mediate the protein-protein interactions. PDZ2 domains of PSD-93 can combine with the carboxyl terminus of NMDAR2 subunits and affect its downstream signal transduction(eg. nitricoxide synthase, nNos). PSD-93 antisense oligodeoxynucleotide(PSD-93 AS DON) is a string of deoxynucleotide sequence and can down regulate the content of PSD-93 protein in postsynaptic membrane of central nervous system at gene level.Objective: To observe the effects of analgesia and morphine tolerance of intrathecal PSD-93 AS ODN on CCI rats and disscuss its mechanism.Methods: Thirty-six rats, regardless of sex, successfully inserted intrathecal cather, were randomly devided into 6 groups(n=6 each ): group F, group MS, group AS, group MA, group Mor. Ischiadic nerve was reset only after 5 minutes' exposure in the air in F group ,while CCI models were established in the rest 5 groups. 4 days after CCI surgery (heat-hyperalgesia and mechanical allodynia is appeared in rats in surgery groups ), intrathecal injection was given, saline (20ul, 2/d,at 8am, 6pm)was given in group F and group NS; morphine (20ug/5ul, bid)+PSD-93 AS DON (5ug/10ul, at 8am), saline (20ul, at 6pm) was given in group MA; PSD-93 AS DON (5ug/10ul, at 8am), saline (20ul, at 6pm) was given in group AS;PSD-93 MS DON (5ug/10ul, at 8am), saline (20ul, at 6pm) was given in group MS . Observe the heat-hyperalgesia and mechanical allodynia in rats 0.5 hour after administration on 1 d before CCI and 1d, 3d, 5d, 6d, 7d, 9d after CCI. 9 days after observation, put them to death and take the L4-6 spinal cord to have immunohistochemistry observation.Result Ethology The difference of mechanical pain threshold and thermalgia threshold before operation in each group is nonsignificant(P>0. 05). Dring the 9 days ,the threshold of mechanical pain and thermalgia of group F almost remain the same as the first day. Dring the first 3 days, The difference of mechanical pain threshold and thermalgia threshold in group AS,group MOR,group MA,group MS,group NS is nonsignificant(P>0. 05),from the 4^th day to the 9^th day after operation , the thresholds of mechanical pain and thermalgia in each group(except group F) are dropped, compared to group AS,group MOR,group MA, group MS and group NS dropped most significantly(P<0. 01). at the 7^th day after operation, the thresholds of mechanical pain and thermalgia in group MOR dropped significantly compared to group MA (P<0. 01),while at the 6^th day after operation, the thresholds of mechanical pain and thermalgia in group AS dropped significantly compared to group MA(P<0. 01). Immunohistochemistry The number of nNOS masculine cell in group AS, group MS and group NS is higher than group F(P<0. 01 ),and the number of nNOS masculine cell in group MA is lower than group AS and group MOR. The number of NMDAR1 in group MOR is higher than group AS,group MA, group MS,group F and group NS (P<0. 01). the number of NMDAR1 masculine cell in group MA is lower than group AS and group MOR.Conclusion 1.In the model of CCI, intrathecal inject 5ug PSD-93 AS ODN showed slight analgesic effect,but lasted no more than 3 days. 2. NMDA R1 and nNOS in cornu dorsale medullae spinalis are related with the central mechanism of morphine tolerance. 3. 5ug PSD-93 AS ODN has some effect on delaying the development of morphine tolerance.