下丘脑室旁核小电导钙激活钾通道过表达降低慢性心衰大鼠肾交感神经兴奋性

 目的：研究下丘脑室旁核小电导钙激活钾通道亚型2（SK2）过表达对慢性心衰大鼠心率、血压和肾交感神经活性的影响，揭示心衰大鼠下丘脑室旁核对交感系统的调节机制。方法：构建SK2重组腺病毒穿梭载体pDC316-mCMV-EGFP-rKCNN2。采用SD大鼠，手术组用左冠状动脉前降支结扎术制作慢性心衰模型，假手术组大鼠左冠状动脉前降支下穿线但不结扎，术后6周用超声心动图测定心功能。心衰组和假手术组分别在室旁核微量注射 SK2 腺病毒pDC316-mCMV-EGFP-rKCNN2和对照腺病毒pDC316-mCMV-EGFP，7 d后通过超声心动图检测心功能的改变；运用免疫组织化学、RT-PCR和Western blotting方法检测SK2重组腺病毒转染情况及表达。室旁核微量注射SK通道阻滞剂apamin,通过PowerLab 8/30系统采集信号记录心率、血压和肾交感神经活性的变化。结果: 心衰大鼠SK2表达较假手术组减少，下丘脑室旁核微量注射SK2腺病毒导致心衰大鼠肾交感神经兴奋性明显降低，下丘脑室旁核微量注射对照腺病毒对假手术大鼠交感神经兴奋性的改变不明显。结论：SK通道蛋白在心衰状态下表达降低并可能导致其功能减弱，进而促成由SK2通道介导的中枢负性交感调节通路的降低，增加了交感神经兴奋性，从而加重心衰的发展。SK2过表达减弱了心衰大鼠的肾交感神经活性，为治疗心衰提供了新的方向。

Over-expression of SK2 channel in PVN reduces renal sympathetic nerve activity in chronic heart failure rats

AIM：To investigate the effect of over-expression of small-conductance calcium-activated potassium channel subtype 2 (SK2) in the paraventricular nucleus (PVN) of hypothalamus on heart rate(HR), mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA)  of the rats with chronic heart failure (CHF). METHODS：Adenovirus vector encoding SK2 (pDC316-mCMV-EGFP-rKCNN2) was constructed.The  CHF model of the male Sprague Dawley (SD) rats was established by the ligation of anterior descending coronary artery. Echocardiogram was used at the 6th week after the operation to identify the CHF model. Adenovirus vector encoding SK2 (pDC316-mCMV-EGFP-rKCNN2) or control adenovirus vector (pDC316-mCMV-EGFP) were transfected into the PVN in vivo. The cardiac function was monitored by echocardiogram. The expression of SK2 at mRNA and protein levels was determined by RT-PCR, Western blotting and immunofluorescence. The HR, MAP and RSNA were measured by PowerLab 8/30 in anesthetized rats with bilateral PVN microinjection of SK channel blocker apamin. RESULTS：Treatment with pDC316-mCMV-EGFP-rKCNN2  significantly decreased the renal sympathetic nerve activity in the rat with CHF. Injection of pDC316-mCMV-EGFP  did not change the renal sympathetic nerve activity in the rats in sham group. CONCLUSION：The expression and function of SK channels in PVN in the heart failure rats were decreased, suggesting a  reduced  negative regulation of sympathetic activity in central neural system. Increased expression of SK2 in the PVN leads to a reduction in sympathetic outflow under the condition of CHF, which may provide a new target for the treatment of heart failure.