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【目的】通过新生期母婴分离(maternal separation,MS)对幼鼠内脏痛觉敏感性影响,观察幼鼠腰骶段脊髓背角Fos表达,探讨新生期MS引起幼鼠内脏痛觉高敏的机制。【方法】按析因设计,32只SD新生大鼠分成4组,每组8只,A1B1组为MS组并在6周龄时接受结直肠压迫(colorectal distention,CRD),A1B2组为MS组,6周龄未给予CRD,A2B1组为对照组并在6周龄接受CRD,A2B2组为对照组,6周龄未给予CRD。A1B1组、A2B1组6周龄时进行CRD刺激下腹外斜肌放电波幅值检测;A1B1组、A2B1组幼鼠CRD接受刺激后2h和A1B2组、A2B2组幼鼠一起处死,留取L6至S2脊髓,应用免疫组织化学染色及计算机图像分析系统进行脊髓Fos阳性(FLI)细胞灰度积分值半定量分析。【结果】CRD压力为0、15、30、45、60、75mmHg时,A1B1组腹外斜肌放电波幅分别为(14.20±1.57)、(26.25±2.93)、(33.84±4.73)、(42.87±5.36)、(47.02±4.86)、(43.16±6.16)μV,A2B1组分别为(13.23±1.47)、(14.62±1.95)、(23.31±5.95)、(33.27±6.70)、(40.90±3.23)、(43.79±8.89)μV;随CRD增加,A1B1、A2B1两组幼鼠腹外斜肌放电波幅均增加;CRD为15、30、45、60mmHg扩张压刺激下,A1B1组腹外斜肌放电幅值显著高于A2B1组(P<0.01)。A1B1、A2B1、A1B2、A2B2组幼鼠腰骶段脊髓背角Fos蛋白阳性细胞灰度积分值分别为88.21±7.28、98.38±6.67、111.32±12.11、127.31±1.78,新生期MS和幼鼠6周龄时CRD均可使幼鼠腰骶段脊髓背角Fos蛋白阳性细胞灰度积分值显著降低,差异均有非常显著意义(F=14.303、56.608,P<0.01)。【结论】新生期MS可导致幼鼠脊髓初级中枢敏化,接受伤害性CRD刺激后能显著引起脊髓神经元Fos蛋白高表达,造成幼鼠痛阈下降,出现慢性内脏痛觉高敏感性,且没有明确的组织病理学改变。
【Objective】 To observe the effect of neonatal maternal separation (MS) on visceral hyperalgesia in young rats and to observe the expression of Fos in lumbosacral spinal dorsal horn of neonatal rats and to explore the mechanism of neonatal MS-induced visceral hyperalgesia in young rats. [Methods] By factorial design, 32 SD neonatal rats were divided into 4 groups of 8 rats each. The A1B1 group was MS group and received colorectal distention (CRD) at 6 weeks of age. The A1B2 group was MS group , 6-week-old did not give CRD, A2B1 group as control group and 6-week-old received CRD, A2B2 group as the control group, 6-week-old did not give CRD. A1B1 group, A2B1 group 6-week-old CRD stimulation of abdominal oblique muscle discharge wave amplitude detection; A1B1 group, A2B1 group of young rats after CRD stimulation 2h and A1B2 group, A2B2 group of young rats were sacrificed, L6 to S2 Spinal cord, immunohistochemical staining and computerized image analysis system were used to semi-quantitatively analyze the gray integral value of Fos-positive cells in spinal cord. 【Results】 The results showed that the amplitude of extracorporeal oblique discharge in A1B1 group was (14.20 ± 1.57), (26.25 ± 2.93), (33.84 ± 4.73) and (42.87 ± 5.32 ± 1.95, 23.31 ± 5.95, 33.27 ± 6.70 and 40.90 ± 3.23, respectively, in the A2B1 group were significantly higher than those in the A2B1 group (5.36, 47.02 ± 4.86 and 43.16 ± 6.16 μV, respectively) (43.79 ± 8.89) μV. With the increase of CRD, the amplitude of extracorporeal oblique discharge in both A1B1 and A2B1 groups was increased. Under the stimulation of 15, 30, 45 and 60 mmHg of CRD, the amplitude of extracorporeal oblique muscle discharge in A1B1 group Significantly higher than A2B1 group (P <0.01). The gray integral values of Fos protein positive cells in the lumbosacral spinal cord in A1B1, A2B1, A1B2 and A2B2 groups were 88.21 ± 7.28,98.38 ± 6.67,111.32 ± 12.11,127.31 ± 1.78, respectively. The neonatal MS and pups were 6 weeks CRD at the age can significantly reduce the integral value of Fos protein positive cells in the lumbosacral spinal dorsal horn of young rats, the differences were significant (F = 14.303,56.608, P <0.01). 【Conclusion】 Neonatal MS can lead to the primary central sensitization of spinal cord in young rats. After receiving nociceptive CRD stimulation, Fos protein expression in spinal cord neurons is significantly increased, resulting in decreased pain threshold and chronic visceral hyperalgesia in rats Clear histopathological changes.