鞘内联合应用吗啡和氯胺酮对神经痛大鼠脊髓NOS活性和NO产量的影响

Effects of intrathecally administered morphine and ketamine on nitric oxide synthase activity and nitric oxide production in the spinal cord

目的观察鞘内联合应用吗啡和氯胺酮对神经痛大鼠脊髓一氧化氮(NO)产量和一氧化氮合酶(NOS)活性的影响。方法 32只Wistar大鼠制成慢性坐骨神经痛模型并随机分为4组,每组8只:对照组(C组),鞘内应用0.9％生理盐水10μl;氯胺酮组(K组),鞘内应用氯胺酮50 μg;吗啡组(M组),鞘内应用吗啡20 μg;吗啡加氯胺酮组(KM组),鞘内应用吗啡10 μg加氯胺酮25μg。每日给药1次,连续7 d。用药后30 min用辐射热刺痛仪测定热痛阈值(即右后肢抬足潜伏期),结果用最大镇痛效应百分率(MPE％)表示。用药7 d后动物处死,取腰段脊髓,用分光光度法测定脊髓NO产量和NOS活性。结果M组和KM组用药后MPE明显高于C组和K组(P<0.01),但随着用药次数的增加,M组的MPE逐渐下降,在用药后第5、6、7天与KM组比较差异有统计学意义(P<0,01)。K组和C组在各时点比较差异亦有统计学意义(P<0.01)。KM组脊髓NO产量和NOS活性均明显低于其他三组(P<0.01或P<0.05)。结论鞘内应用吗啡和氯胺酮可对抗神经痛大鼠对辐射热的痛觉过敏反应,对防治中枢神经敏感化的进一步形成和发展有一定作用,具有临床应用潜能。

Objective To study the effects of intrathecally administered morphine and ketamine on nitric oxide synthase (NOS) activity and nitric oxide content in the spinal cord.Methods Thirty-two male Wistar rats weighing 220-260 g were anesthetized with intraperitoneal chloral hydrate 300 mg·kg-1 . A catheter was implanted in subarachnoid space at lumbal region. Sciatic constriction injury (SCI) was produced by loose ligation of right sciatic nerve trunk with 4-0 cutgut. On the 4th postoperative day the animals were randomly divided into four groups of 8 animals :(1) control group (C); (2) morphine group (M);(3) ketamine group (K) and morphine-ketamine group (KM) . Morphine 20 μg / ketamine 20 μg / morphine 10 μg + ketamine 10 μg were injected intrathecally every day for 7 consecutive days in group M, K and KM. In control group normal saline was injected intrathecally instead of morphine and / or ketamine. The withdrawal latenvies to radiant heat focused on plantar surface were measured as radiant heat threshold before intrathecal administration of the analgesic (baseline) and 30 min after intrathecal administration of ketamine and / or morphine every day for 7consecutive days. The percentage of maximal possible effect ( MPE % ) was calculated : MPE % = (latency after intrathecal administration-baseline latency) / (radiant heat cut-off time-baseline latency) X 100% . After 7 days of intrathecal administration the animals were decapitated and the spinal cord was immediately removed and the lumbal spinal cord was dissected on ice. NOS activity and nitric oxide ( NO) content were measured by spectrophotometry. Results MPE % was significantly higher in group M and KM than in group C and K ( P < 0.01 ) . As intrathecal administration continued MPE% was gradually decreasing in group M and there was significant difference in MPE% on the 5th, 6th and 7th day between group M and KM ( P < 0.01). MPE% was significantly higher in group K than that in control group (P <0.01). NOS activity and NO content in the spiral cord were significantly lower in group KM than in the other three groups. Conclusion Morphine and ketamine administered intrathecally can reduce thermal hyperalgesia. Morphine and ketamine administered in combination provide better effect.