银杏内酯通过激活Nrf2和CREB核转位促进抗氧化和抗凋亡基因表达发挥抗脑缺血再灌注损伤作用

目的研究银杏二萜内酯葡胺注射液(DGMI)抗大鼠脑缺血再灌注损伤的作用及机制。方法建立大鼠脑缺血再灌注损伤模型,缺血1.5 h,再灌注24 h后对神经行为学缺损程度评分,TTC测定大鼠脑梗死体积,Western印迹和免疫荧光测定大鼠脑组织中蛋白表达。结果 DGMI能够显著改善脑缺血再灌注损伤导致的大鼠神经行为学缺损症状,提高运动神经功能,减小脑梗死体积及水肿程度,抑制受损脑区的神经元凋亡。一方面,DGMI能够激活PI3K/Akt/Nrf2通路,促进Nrf2的核转位,增加HO-1蛋白的表达,提高受损脑区中Neu N与Nrf2双阳性细胞的百分比。另一方面,DGMI也能够激活PI3K/Akt/CREB通路,提高CREB磷酸化水平和受损脑区中Neu N与p-CREB双阳性细胞的百分比。结论 DGMI通过激活PI3K/Akt/Nrf2和PI3K/Akt/CREB通路共同发挥抗脑缺血再灌注损伤作用。     

C3G通过PKA/CREB信号通路减轻成年小鼠SAH后早期脑损伤

目的 探讨矢车菊素-3-O-葡萄糖苷（C3G）对小鼠蛛网膜下腔出血（SAH）后早期脑损伤（EBI）的影响及作用机制。方法 取72只雄性C57小鼠随机分成6组:假手术组、SAH组、溶剂组、低剂量C3G组（10 mg/kg）、中剂量C3G组（（20 mg/kg）、高剂量C3G组（30 mg/kg）;每组12只。应用颈动脉穿刺法制作小鼠SAH模型,术后24 h进行Garcia评分和平衡木评分评估神经功能;每组小鼠随机取6只取外周血检测活性氧（ROS）和丙二醛（MDA）含量,然后取出完整脑组织进行SAH出血评分、脑水含量检测;每组剩余6只小鼠取外周血检测GSH/GSSG水平,然后取脑组织应用免疫印迹法检测PKA、p-PKA、CREB、p-CREB和GCLC表达水平。结果 与假手术组相比,SAH组小鼠神经功能评分明显下降（P<0.05）,脑水含量、SAH出血评分、外周血ROS和MDA含量均显著增加（P<0.05）,外周血GSH/GSSG比值明显下降（P<0.05）,脑组织p-PKA、p-CREB和GCLC表达明显上调（P<0.05）。C3G明显增加小鼠神经功评分（P<0.05）,明显降低SAH评分降低、脑含水量（P<0.05）,明显降低外周血ROS、MDA含量（P<0.05）,明显增加外周血GSH/GSSG比值（P<0.05）,明显下调脑组织p-PKA、p-CREB和GCLC表达（P<0.05）。结论 C3G明显改善小鼠SAH后EBI,其机制可能是抑制PKA/CREB信号通路,下调GCLC表达,进而抑制氧化应激损伤。     

Chronic antidepressant treatment selectively increases expression of plasticity-related proteins in the hippocampus and medial prefrontal cortex of the rat

Antidepressants protect against hippocampal volume loss in humans and reverse stress-induced atrophic changes in animals thus supporting the hypothesis that the pathophysiology of stress-related disorders such as depression involves reductions in neuronal connectivity and this effect is reversible by antidepressant treatment. However, it is unclear which brain areas demonstrate such alterations in plasticity in response to antidepressant treatment. The aim of the present study was to examine the effect of antidepressant treatment on the expression of three plasticity-associated marker proteins, the polysialylated form of nerve cell adhesion molecule (PSA-NCAM), phosphorylated cyclic-AMP response element binding protein (pCREB) and growth-associated protein 43 (GAP-43), in the rat brain. To this end, rats were treated either acutely (60 min) or chronically (21 days) with imipramine (30 and 15 mg/kg, respectively) and the expression of PSA-NCAM, pCREB, and GAP-43 was assessed using immunohistochemistry. Initial mapping revealed that chronic imipramine treatment increased expression of these plasticity-associated proteins in the hippocampus, medial prefrontal cortex and piriform cortex but not in the other brain regions examined. Since PSA-NCAM and pCREB are expressed in recently-generated neurons in the dentate gyrus, it is likely that chronic imipramine treatment increased their expression in the hippocampus at least partially by increasing neurogenesis. In contrast, since chronic imipramine treatment is not associated with neurogenesis in the medial prefrontal cortex, increased expression of PSA-NCAM and pCREB in the prelimbic cortex implicates changes in synaptic connectivity in this brain region. Acute treatment with imipramine increased the number of pCREB positive nuclei in the hippocampus and the prefrontal cortex but did not alter expression of GAP-43 or PSA-NCAM in any of the brain regions examined. Taken together, the results of the present study suggest that antidepressant treatment increases synaptic plasticity and connectivity in brain regions associated with mood disorders.     

Dynamic interplays between memory systems depend on practice: the hippocampus is not always the first to provide solution

Previous studies showed that the optimization of behavioral performance through extended training depends on a switch from hippocampus-based memory to striatum-based habit. Here we investigate whether the amount of training within one learning session influences the retention of memory for hippocampal versus striatal strategies. Mice were trained to search for a submerged cue-marked platform which remained in the same spatial location in the water-maze for each of three training regimens (4, 12 or 22 trials). Subsequently, they were either tested for retention of memory 1 h or 24 h later on a probe test or killed at different time points over a 7-h period to determine the kinetic of cAMP response element binding protein (CREB) phosphorylation in both memory systems. During the probe test mice had to choose between a submerged platform located in the same position as during the acquisition phase (spatial solution) and a platform marked by the cue but located in the opposite quadrant of the pool (cue-guided solution). Results showed that the animals first preferred the cue-marked platform, which represents a strategy that was selectively impaired by lesions of the dorsolateral caudate-putamen. With further practice, or context pre-exposure, animals transiently favored the hippocampus-dependent place solution but finally, both strategies became interchangeable and insensitive to either lesion. CREB phosphorylation increased in both memory systems following acquisition but training-dependent changes selectively occurred in the hippocampus wherein biphasic activation was initiated by the four-trial training and blocked by training for 22 trials. These findings indicate that learning in one session consists of three acquisition stages with parallel engagement of multiple memory systems at the beginning of learning. They suggest, however, that, in a later phase, dynamic interplays promote the use of the most adapted brain system depending on practice and this is accompanied by specific patterns of CREB phosphorylation in the hippocampus.