内脏高敏感大鼠结肠特异背根神经节神经元TRPV1表达和电生理特征变化

Expression of TRPV1 and Electrophysiological Characteristics of Colon-specific Dorsal Root Ganglion Neurons in Rat Model of Visceral Hypersensitivity

背景:内脏高敏感被认为是肠易激综合征的主要病理生理机制之一。目的:探讨内脏高敏感大鼠结肠特异背根神经节(DRG)神经元上的TRPV1表达及其电生理特征。方法:20只10 d龄大鼠随机分为模型组和对照组,模型组以结直肠内灌注乙酸诱导内脏高敏感模型,对照组灌注等量0.9%NaC l溶液。以结肠壁注射DiI荧光染料逆行标记DRG神经元(即结肠特异DRG神经元),免疫荧光法检测DRG神经元上的TRPV1表达,膜片钳技术记录神经元电生理特征。结果:模型组结肠特异DRG神经元上的TRPV1表达阳性率明显高于对照组(46.1%对36.6%,P<0.01),平均阈电流值明显低于对照组[(57.80±1.32)pA对(73.45±4.51)pA,P<0.05],2倍阈电流刺激下动作电位频率明显高于对照组[(8.20±1.10)Hz对(4.54±0.66)Hz,P<0.05],差异均有统计学意义。模型组60 mm Hg结直肠扩张压力下的腹壁回撤反射(AWR)评分与TRPV1表达阳性率、2倍阈电流刺激下动作电位频率呈正相关(r=0.87和r=0.73,P<0.01),与阈电流值呈负相关(r=-0.81,P<0.01)。结论:结肠特异DRG神经元TRPV1表达上调、细胞兴奋性增加,可能是内脏高敏感形成的重要环节。

Background：Visceral hypersensitivity is considered to be one of the major pathophysiological mechanisms of irritable bowel syndrome. Aims：To investigate the expression of TRPV1 and electrophysiological characteristics of colon-specific dorsal root ganglion（ DRG）neurons in rat model of visceral hypersensitivity. Methods：Twenty 10-day-old rats were randomly divided into two groups. In model group,visceral hypersensitivity was induced by colorectal administration of acetic acid;while in control group the same amount of saline was administered. Colon-specific DRG neurons were labeled retrogradely by injection of DiI,a fluorochrome,into the colon wall. Expression of TRPV1 in DRG neurons was detected by immunofluorescence and the electrophysiological characteristics of DRG neurons was detected by using patch-clamp technique. Results：In model group,the expression rate of TRPV1 in colon-specific DRG neurons was significantly higher than that in controls（46. 1% vs. 36. 6% ,P 〈0. 01）,the average rheobase was significantly decreased[（57. 80 ±1. 32）pA vs.（73. 45 ± 4. 51）pA,P 〈 0. 05],while the frequency of action potentials（APs）in response to doubling rheobase stimulation was significantly increased[（8. 20 ± 1. 10）Hz vs. （4. 54 ± 0. 66）Hz,P 〈 0. 05]. Score of abdominal withdrawal reflex（AWR）under a 60 mm Hg colorectal distention was positively correlated with the expression rate of TRPV1 and the frequency of APs in response to doubling rheobase stimulation（r = 0. 87 and r = 0. 73,P 〈 0. 01）,but was negatively correlated with the rheobase（r = - 0. 81,P 〈 0. 01）in model group. Conclusions：Increased expression of TRPV1 and excitability in colon-specific DRG neurons might be a crucial step in formation of visceral hypersensitivity.