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目的:评价吗啡对电刺激坐骨神经诱发新生期大鼠脊髓背角浅层长时程增强(LTP)的影响。方法:雄性SD大鼠20只,日龄18-21d,体重60-65g,随机分为对照组、吗啡组(M组)、纳洛酮组(N组),纳洛酮+吗啡组(MN组),每组8例。麻醉下分离左侧坐骨神经,记录电极插于左侧T13-L1脊髓背角浅层,刺激电极刺激左侧坐骨神经,给予4V、0.5ms、1/60Hz单个方波电刺激30min以诱发场电位,抽取生理盐水10μl、吗啡10μl(15μg/μl)、纳洛酮10μl(2.5μg/μl)、纳洛酮(2.5μg/μl)和吗啡(15μg/μl)各5μl的混合液,在脊髓上方3mm,经2min内缓慢滴注,给药后5min时,给予4串条件电刺激(8V、0.5ms、100Hz、串长1s、串间隔10s)后,再给予单个方波电刺激120min以上,记录强直刺激前30min、条件电刺激后0-30,35-60,65-120min时段平均场电位幅值及潜伏期。结果:与强直刺激前30min比较,C组和N组A类特征的波在强直刺激后各时段平均场电位幅值升高,潜伏期缩短,M组A类特征的波在强直刺激后各时段平均场电位幅值降低,潜伏期延长,MN组A类特征的波在强直刺激后0-30min平均场电位幅值升高,潜伏期缩短,35-120min时段平均场电位幅值降低,潜伏期延长,以上P<0.05或0.01,C类特征的波在刺激前后变化不明显。结论:吗啡可抑制电刺激新生期大鼠坐骨神经诱发脊髓背角以A类特征波的突触LTP,可能是其所处神经发育阶段决定的。
AIM: To evaluate the effect of morphine on the long-term potentiation (LTP) of spinal dorsal horn induced by electrical stimulation of sciatic nerve in neonatal rats. Methods: Twenty male SD rats aged 18-21 days and weighing 60-65g were randomly divided into control group, morphine group (M group), naloxone group (N group), naloxone + morphine group (MN group) Group), 8 cases in each group. The left sciatic nerve was isolated under anesthesia. The recording electrode was inserted into the superficial layer of spinal dorsal horn on the left side of T13-L1. The stimulation electrode stimulated the left sciatic nerve. Single square wave stimulation of 4V, 0.5ms, 1/60 Hz for 30min was used to induce field potential. 10 μl of morphine (15 μg / μl), 5 μl of naloxone (2.5 μg / μl), 5 μl of naloxone (2.5 μg / μl) and morphine (15 μg / μl) Four minutes after the administration of 5-min electrical stimulation (8V, 0.5ms, 100Hz, string length 1s, string interval 10s), the rats were given a single square wave electrical stimulation for more than 120 minutes, The mean field potential amplitude and latency at 0-30, 35-60 and 65-120 min after the first 30 min of electrical stimulation. Results: Compared with 30 minutes before tetanic stimulation, the A-wave characteristics in group C and group N increased mean field potential amplitude and shorten the incubation period after tonic stimulation, The amplitude of field potential decreased and the latency prolonged. In group MN, the mean field potential amplitude increased from 0-30 minutes after tetanic stimulation, and the incubation period was shortened. The average field potential amplitude was decreased and the incubation period was longer in 35-120 minutes, <0.05 or 0.01, C wave characteristics before and after stimulation did not change significantly. CONCLUSION: Morphine can inhibit the synaptic LTP induced by type A characteristic wave in spinal dorsal horn induced by electrical stimulation of neonatal rat sciatic nerve, which may be determined by the neurodevelopmental stage.