鞘内注射神经激肽-1受体激动剂Sar-SP增强大鼠脊髓一氧化氮合酶表达和一氧化氮生成

探讨P物质(substance P,SP)对脊髓一氧化氮合酶(nitric oxide synthase,NOS)表达和一氧化氮(nitric oxide,NO)生成的影响。实验用热甩尾法测定大鼠痛阈的变化,分别应用NADPH-d组织化学法和硝酸还原法测定大鼠脊髓内NOS表达和NO生成的变化。结果显示,鞘内注射神经激肽-1受体(neurokinin-1 receptor,NK-1)激动剂Sar^9,Met(O2)^11]-substance P(Sar-SP)可使大鼠痛阈降低,脊髓后角浅层和中央管周围灰质内NOS表达增强,脊髓腰膨大部位NO生成增多;预先鞘内注射非选择性NK-1受体拮抗剂D—Arg^1,D-Trp^7,9,Leu^11]-substance P(spantide)可抑制上述变化。结果表明,SP可促进脊髓内NOS表达和NO生成。

Intrathecal injection of Sar9, Met(O2)11-substance P, neurokinin-1 receptor agonist, increases nitric oxide synthase expression and nitric oxide production in the rat spinal cord

In the spinal cord, nitric oxide (NO) pathway is involved in pain and hyperalgesia, and nitric oxide synthase (NOS) expression and NO production are upregulated following several noxious and lesion stimuli. However, the mechanism of the increases is yet not well understood. The present study was designed to address the question of whether substance P (SP) released in the spinal cord enhances NOS expression and NO production of the spinal cord in rats. Sar(9), Met(O2)(11)]-substance P (Sar-SP), a neurokinin-1 (NK-1) receptor agonist, was administered by intrathecal injection via L(5)-L(6) intervertebral space to induce nociception. The pain threshold was determined by hot water induced tail flick test. NOS expression of the L(5) segment of the spinal cord was determined using NADPH-d histochemical staining. NO production of the lumbar enlargement of the spinal cord was determined by assaying NO3(-) and NO2(-), the end product of NO metabolism, using the method of aqua fortis reduction. We found that (1) intrathecal injection of Sar-SP (6.5 nmol) elicited a characteristic, caudally directed, nociceptive behavioural response consisting of intense biting, licking and scratching episodes. Tail flick test showed decrease in pain threshold. (2) following the behavioural responses, the NOS expression level, including the number and the staining density of the NADPH-d reactive cells, increased in the superficial portion of the dorsal horn (Laminae I-II) and the grey matter surrounding the central canal (LaminaX) of the L(5) segment of the spinal cord after the Sar-SP intrathecal injection. At the same time, NO production in the enlargement of the spinal cord increased. (3) The decreased pain threshold and the increases in NOS expression and NO production could be substantially inhibited by intrathecal injection of D-Arg(1), D-Trp(7,9), Leu(11)]-substance P] (spantide) (5 microg), a non-selective antagonist of NK-1 receptor, 5 min prior to the Sar-SP injection. It might be concluded that the release of SP resulted from nociceptive afferents increased NOS expression and NO production of the rat spinal cord.