抑郁引起大鼠结肠动力学改变导致肠易激综合征的离子通道机制

Mechanisms of ion channel in irritable bowel syndrome caused by depression induced abnormal colon motility in rats

目的探讨抑郁引起大鼠结肠动力学改变导致 IBS 的离子通道机制。方法将 SPF级成年雄性 SD 大鼠分为对照组和抑郁组，各15只。抑郁模型制备采用慢性温和不可预知应激刺激方式，28 d 后经旷场实验和液体消耗实验（FCT ）确定抑郁模型成功。根据临床表现、粪便性状和数量确定胃肠道反应，计算腹壁回撤反射阈值，评估结直肠扩张的敏感性变化，确定 IBS 发生率。酶解法分离单个结肠平滑肌细胞，全细胞膜片钳技术记录 ICa‐L 改变及其动力学特征变化。两两比较采用 t 检验，相关性分析采用 Pearson 法。结果与对照组比较，抑郁组大鼠体质量、旷场实验和 FCT 各测试值均显著降低。抑郁组大鼠排便颗粒数及其含水量明显增加，容量阈值显著降低，与旷场实验和 FCT 呈显著负相关（r＝－0．89、0．91，P均＜0．01），IBS 发生率为14／15。与对照组比较，抑郁组大鼠结肠平滑肌细胞膜上 ICa‐L 明显增大，对照组 ICa‐L 为（－21．31±4．79） pA ，抑郁组 ICa‐L 为（－33．52±4．45） pA ，且与抑郁大鼠排便颗粒数及其含水量呈显著正相关（r ＝0．91、0．91， P 均＜0．01）。对照组电流电压特性曲线（I‐V曲线）处在中部，抑郁组处在最底部。抑郁组 L‐型钙通道激活曲线显著左移，最大半激活电压由对照组的（－7．96±5．95） mV 减小为（－14．81±3．33） mV ；失活恢复电流明显增快，最大半失活恢复时间由对照组的（393．28±41．79） ms 缩短为（163．29±27．34） ms ，提前了58．48％。结论抑郁可引起大鼠胃肠道出现明显 IBS ，其发生机制可能是抑郁引起结肠平滑肌细胞膜上 ICa‐L 异常增加，激活离子通道提前开放，失活恢复时间增快，使 L‐型钙通道发生电重构。

Objective To investigate mechanisms of ion channel in irritable bowel syndrome （IBS） caused by depression induced abnormal colon motility in rats .Methods Adult male SD SPF rats were divided into control group and depression group ,15 rats in each group . The depression models were induced by chronic unpredictable mild stress stimulation .After 28 days ,the success of depression model was confirmed by open field test （OFT） and fluid consumption test （FCT ） .The gastrointestinal reaction was determined by clinical symptoms ,fecal character and times .Abdominal contraction reflex threshold was calculated to evaluate the changes of visceral sensitivity after colorectal distention and to determine the incidence of IBS .Single rat colonic myocytes were isolated by enzyme method .The changes of L‐type calcium current （ICa‐L ） and kinetics properties were recorded via whole‐cell patch clamp technique .The t test was performed for comparison between two groups and Pearson method was for correlation analysis . Results Compared with control group ,the body weight ,OFT and FCT of the rats in depression group were significantly decreased . The rats of depression group have severe body weakness symptoms , the particle number and water content of fecal increasing ,capacity threshold significantly decreased and which was negative correlated with OFT and FCT （r= - 0 .89 and 0 .91 ,both P〈 0 .01） .The incidence of IBS was 14/15 . Compared with control group , ICa‐L of colonic myocytes of rats in depression group was significantly increased ,ICa‐L of control group was （ - 21 .31 ± 4 .79） pA and that of depression group was （ - 33 .52 ± 4 .45） pA ,and which was positive correlated with the particle number and water content of fecal of depression rats （r= 0 .91 and 0 .91 ,both P〈 0 .01） .Moreover the current‐voltage （I‐V ） curve of control group was at middle and of depression group was at the bottom .The steady‐state activation curve of ICa‐L of depression group markedly left shifted ,and the maximum half activated voltages decreased from （ - 7 .96 ± 5 .95） mV of control group to （ - 14 .81 ± 3 .33） mV .Moreover ,recovery of inactivation of ICa‐L was fast ,the recovery time of maximum half inactivation was shorten from （393 .28 ± 41 .79 ） ms of control group to （163 .29 ± 27 .34） ms ,58 .48% in advance .Conclusions Depression could induce obvious IBS in gastrointestinal of rats . The mechanisms maybe depression causes ICa‐L of colonic myocytes abnormally increasing ,steady‐state activation gate open in advance ,accelerate recovery time of inactivation and ion channel remodeling of ICa‐L .