Inhalation anesthetics suppress c-Fos expression evoked by noxious somatic stimulation in rat spinal cord dorsal horn neurons

本实验观察了吸入麻醉剂安氟醚、异氟醚和七氟烷对福尔马林诱导的大鼠脊髓c-Fos蛋白表达的影响。雄性SD大鼠随机分为4组：100%氧气对照组(n=6)、3.3%安氟醚(1.5MAC，N=6)、2.1%异氟醚(1.5MAC，N=6)、4.0%异氟醚(1.5MAC，N=6)、七氟醚(1.5MAC，n=6)。然后每只大鼠都接受了S.C.左侧后爪注射5/o Formahn 100μ-1，维持麻醉。三个小时后，大鼠被处死并灌胃。用抗c-Fos抗体对脊髓LL6节段进行免疫组织化学染色。在L3和L4节段，安氟醚组、异氟醚组和七氟醚组的Fos样免疫反应细胞数比对照组减少了40%~50%(p&lt；0.05)。这种减少主要出现在背角深层(III~VI层)和腹侧灰质(VII~X层)，而不是存在于浅层(I~II层)的神经元。这一结果与前人有关氟烷的研究结果一致。这些表明，大多数吸入麻醉剂对更深层的脊髓神经元有影响，其中一些直接接受伤害性输入。我们的研究未能证实先前的发现，即安氟醚和七氟烷增强了伤害性刺激引起的传入信号。

The effects of inhalation anesthetics, enflurane, isoflurane, and sevoflurane, on the expression of c-Fos protein evoked by formalin injection were studied in the spinal cord in the rat. Male Sprague-Dawley rats were allocated to four treatment groups: 100% oxygen (control, n=6), 3.3% enflurane (1.5MAC, N=6), 2.1% isoflurane (1.5MAC, N=6)4.0%, sevoflurane (1.5 MAC, n=6) for 30 nun. Each rat then received a s.c. inject of 5/o formahn 100μ1 into the left hind paw and anesthesia was maintained. Three hours later the rats were sacrificed and perfused. Section of the Ll〜6 level of spinal cord were immunostained with anti c-Fos antibody. We counted the number of Fos-like immunoreactive (FLI) cells in every specific lamina.In the sections of L3 and L4 level, the numbers of FLI labeled neurons for groups given enflurane, isoflurane, and sevoflurane were 40 to 50 % less than the control (p<0.05). The decrease occurred predominantly in the deeper layer of the dorsal horn (laminae III〜VI) and ventral gray (laminae VII〜X) but not on the neurons existed in superficial layer (laminae I〜II).This finding was consistent with the results of the previous studies concerned with halothane. These suggested that most inhalation anesthetics have effects on spinal neurons in the deeper layers, some of which directly receive noxious inputs. Our study failed to confirm previous findings that enflurane and sevoflurane augment the afferent signals evoked by the noxious stimulation.