鞘内预先应用N^G-硝基-L-精氨酸-甲基酯可选择性抑制坐骨神经电刺激诱发的大鼠脊髓后角深层c-fos表达

INTRATHECAL PRE-ADMINISTRATION OF L-NAME CAN SELECTIVELY INHIBIT C-FOS EXPRESSION IN DEEP LAMINAE OF SPINAL DORSAL HORN EVOKED BY ELECTRICAL STIMULATION IN SCIATIC NERVE IN RATS

目的:观察鞘内预先应用非选择性NOS抑制剂-L-NAME对电刺激坐骨神经诱发大鼠脊髓后角c-fos表达的影响。方法:选择鞘内置管后无神经损伤症状的雌性SD大鼠24只,将其随机平均分为4组。半数动物实施假手术,术前15 min向鞘内分别注射10μl生理盐水(A组)或L-NAME 250μg(B组);另一半动物实施坐骨神经电刺激1 h,术前15 min向鞘内分别注射10μl生理盐水(C组)或L-NAME 250μg(D组)。分别在鞘内给药前(T0)和术后4 h(T1)、12 h(T2)和24h(T3)测量各组大鼠的热甩尾潜伏时间(TFL);术后24 h处死动物,采用免疫组化法检测其脊髓后角内FLI神经元的数目。另取4只大鼠处死作为脊髓免疫组化检查的对照。结果:在坐骨神经电刺激后12 h和24 h,C组大鼠的TFL分别较术前缩短45%和39%;而在D组,这种降低已不再显著。与A、B两组的绝大多数FLI神经元是集中在脊髓后角浅层的情况不同,C组大鼠在脊髓后角深层亦出现了大量FLI神经元,大约占脊髓后角FLI神经元总数的33%;与C组相比,虽然D组脊髓后角浅层和固有层的FLI神经元数目降低不显著,但是其脊髓后角深层的FLI神经元数目却出现了显著降低(P<0.05)。结论:鞘内预先应用L-NAME可选择性抑制坐骨神经电刺激诱发的大鼠脊髓后角深层c-fos的表达,减弱或阻断机体热痛阈的下调。

Objective ： To observe the effect of intrathecal pre-administration of L-NAME, a non-selective NOS inhibitor, on the c-fos expression in spinal dorsal horn following electrical stimulation of sciatic nerve in rats. Method ： 24 healthy female Sprague-Dawley rats, who had no signs of neurological deficien- cy after intrathecal catheter, were divided into 4 groups equally. In half of all animals, 10 μl of normal saline （group A） or L-NAME 250 μg （group B） were injected intrathecally 15 rain before sham operation;for the other half of animals, 10μl of normal saline （group C） or L-NAME 250 μg（group D） were injected intratbecally 15 rain before electrical stimulation of sciatic nerve for one hour. The thermal threshold was observed by measuring tail-flick latency （TFL） before experiment, and 4 h, 12 h and 24 h after electrical stimulation of sciatic nerve or sham operation. 24 h later, all animals were euthanazed and the number of los-like immunoreactivity （FLI） neurons in ipsilateral spinal dorsal horn were detected by immunohistochemistry technique. 4 other rats were sacrificed and served as control of spinal immuno- histochemistry. Result： In group C, TFL at 12 h and 24 h following electrical stimulation were reduced by 45% and 39%, respectively, while such decreases did not reach statistic significance in group D. Contrary to groups A and B where the majority of FLI neurons lies predominately in the superficial laminae of spinal dorsal horn, there appeared a lot of FLI neurons in the deep laminae of spinal dorsal horn in group C, which approximately occupied 33% of the total FLI neurons. In comparison with group C, in group D, the number of FLI neurons did not decrease significantly in the superficial laminae and nucleus proprius of dorsal horn （ P 〉0.05 ） , but decreased significantly in the deep laminae of dorsal horn （ P 〈 0.05）. Conclusion ： Intrathecal pre-administration of L-NAME can selectively inhibit the c-fos expression in deep laminae of spinal dorsal horn evoked by electrical stimulation of sciatic nerve, effectively attenuating or preventing its down-regulation of thermal threshold.