大鼠机械通气致脑损伤时脑组织γ-氨基丁酸信号通路活性的变化

Changes in activation of γ-aminobutyric acid signaling pathway during ventilator-induced brain injury in rats

目的评价大鼠机械通气致脑损伤时脑组织γ-氨基丁酸（GABA）信号通路活性的变化。 方法清洁级成年雄性SD大鼠36只，体重280～320 g，采用随机数字表法分为3组（n＝12）：小潮气量通气组（LV组）、大潮气量通气2 h组（HV1组）和大潮气量通气6 h组（HV2组）。LV组潮气量10 ml/kg、通气频率40次/min、通气时间2 h；HV1组潮气量40 ml/kg、通气频率40次/min、通气时间2 h；HV2组潮气量40 ml/kg、通气频率40次/min、通气时间6 h。于机械通气结束时取血标本，采用ELISA法测定血清神经元特异性烯醇化酶（NSE）和S100β蛋白浓度。随后处死6只大鼠，取脑组织，采用ELISA法测定IL-1β和TNF-α含量，采用Western blot法检测谷氨酸脱羧酶（GAD）和GABAA受体（GABAAR）的表达水平。通气结束后第2天进行Morris水迷宫实验。 结果与LV组比较，HV1组与HV2组血清NSE和S100β蛋白浓度、脑组织IL-1β和TNF-α含量升高，GAD和GABAAR表达上调，逃避潜伏期延长，原平台象限游泳距离百分比降低（P〈0.05）；与HV1组比较，HV2组血清NSE和S100β蛋白浓度、脑组织IL-1β和TNF-α含量升高，GAD和GABAAR表达上调，逃避潜伏期延长，原平台象限游泳距离百分比降低（P〈0.05）。 结论机械通气诱发大鼠脑损伤时脑组织GABA信号通路活化水平增强，该变化可能参与了机械通气诱发脑损伤的病理生理机制。

Objective To evaluate the changes in activation of γ-aminobutyric acid （GABA） sig- naling pathway during ventilator-induced brain injury in rats. Methods Thirty-six pathogen-free adult male Sprague-Dawley rats, weighing 280-320 g, were divided into 3 groups （n = 12 each） using a random number table： low tidal volume group （LV group）, ventilation with high tidal volume for 2 h group （HV1 group） and ventilation with high tidal volume for 6 h group （ HV2 group）. The rats were mechanically ven- tilated for 2 h with the tidal volume set at 10 ml/kg and the respiratory rate 40 breaths/min in group LV. The rats were mechanically ventilated for 2 h with the tidal volume set at 40 ml/kg and the respiratory rate 40 breaths/min in group HV1. The rats were mechanically ventilated for 6 h with the tidal volume set at 40 ml/kg and the respiratory rate 40 breaths/min in group HV2. Blood samples were collected at the end of ven- tilation for determination of serum neuron-specific enolase （NSE） and S10013 protein concentrations by en- zyme-linked immunosorbent assay. Six rats were then sacrificed and their brains were removed for determi-nation of intedeukin-1β （IL-1β） and tumor necrosis factor-a （TNF-cx） contents （by enzyme-linked im- munosorbent assay） and expression of glutamic acid decarboxylase （ GAD ） and GABAA receptors （ by Western blot）. Morris water maze test was performed on 2nd day after the end of ventilation. Results Compared with group LV, the serum concentrations of NSE and S10013 protein and contents of IL-lβ and TNF-a were significantly increased, the expression of GAD and GABAA receptors was up-regulated, the es- cape latency was prolonged, and the percentage of swimming distance at the original platform was decreased in HV1 and HVz groups （P〈0. 05）. Compared with group HV1, the serum concentrations of NSE and S10013 protein and contents of IL-lβ and TNF-a were significantly increased, the expression of GAD and GABAA receptors was up-regulated, the escape latency was prolonged, and the percentage of swimming distance at the original platform was decreased in group HV2 （ P〈0. 05）. Conclusion Activation of GABA signaling pathway is enhanced during ventilator-induced brain injury, which may be involved in the patho- physiological mechanism of ventilator-induced brain irjury in rats.