The effect of α7 nicotinic receptor activation on glutamatergic transmission in the hippocampus

Nicotinic acetylcholine receptors (nAChRs) are expressed widely in the CNS, and mediate both synaptic and perisynaptic activities of endogenous cholinergic inputs and pharmacological actions of exogenous compounds (e.g., nicotine and choline). Behavioral studies indicate that nicotine improves such cognitive functions as learning and memory, however the cellular mechanism of these actions remains elusive. With help from newly developed biosensors and optogenetic tools, recent studies provide new insights on signaling mechanisms involved in the activation of nAChRs. Here we will review α7 nAChR’s action in the tri-synaptic pathway in the hippocampus. The effects of α7 nAChR activation via either exogenous compounds or endogenous cholinergic innervation are detailed for spontaneous and evoked glutamatergic synaptic transmission and synaptic plasticity, as well as the underlying signaling mechanisms. In summary, α7 nAChRs trigger intracellular calcium rise and calcium-dependent signaling pathways to enhance glutamate release and induce glutamatergic synaptic plasticity.     

高压氧治疗对阿尔茨海默病大鼠海马内神经元凋亡及p38丝裂原蛋白激酶表达的影响

目的 评价高压氧治疗对阿尔茨海默病(alzheimer's disease,AD)大鼠海马内神经元凋亡及p38丝裂原蛋白激酶(p38 mitogenactivated protein kinases,p38MAPK)表达的影响. 方法 18只雄性SD大鼠,体重260 g～290 g,采用随机数字表法分为3组(每组6只):生理盐水组(NS组),海马区注射生理盐水;阿尔茨海默病组(AD组),海马区注射Aβ1-40;高压氧组(HBO组),海马区注射Aβ1-40,并于术后1 d～7d行每天1次的高压氧治疗.应用脑立体定位仪于大鼠海马区注射Aβ1-40制备AD模型.于术前1d和术后1、7、14、21 d行水迷宫行为学测试.于术后21 d水迷宫行为学测试结束后处死大鼠,采用苏木精-伊红染色(hematoxylin-eosin,HE)方法染色海马组织病理结构,TUNEL法标记检测凋亡细胞,免疫印迹法(Western bolt)法测定海马内p38MAPK蛋白磷酸化水平. 结果 术后21 d时,与NS组比较,AD组大鼠上台前路程和逃避潜伏期增加[(379±41)、(1 978±120) cm,(16.0±2.8)、(78.4±10.8)s](P＜0.05);与AD组比较,HBO组大鼠上台前路程和逃避潜伏期减少[(1978±120)、(1 246±96) cm,(78.4±10.8)、(51.7±6.2)s](P＜0.05).与NS组比较,AD组和HBO组大鼠海马组织细胞凋亡率[(6.3±13)％,(45.2±5.1)％]及p38MAPK蛋白磷酸化表达升高(0.16±0.06),(0.54±0.10)(P＜0.05);与AD组比较,HBO组海马组织细胞凋亡率[(45.2±5.1)％,(22.5±3.7)％]及p38 MAPK蛋白磷酸化表达下降[(0.54±0.10),(0.31±0.08)](P＜0.05).结论 高压氧治疗可有效缓解AD大鼠认知功能障碍,且能够抑制海马内神经元凋亡,其机制与降低p38MAPK的磷酸化水平有关.     

Effect of tube feeding on hippocampal-dependent memory in SAMP1 mice

This study examined the effect of tube feeding on hippocampal Fos induction and spatial performance in a water maze task in senescenceaccelerated mice (SAMP1). Tube feeding accelerated the age-related decline in spatial memory and decreased Fos induction in the hippocampal CA1 region in aged SAMP1 mice. The results suggest that tube feeding in aged SAMP1 mice reduces input activity in the hippocampus, thereby leading to senile memory deficits.     

Anterior thalamic nuclei deep brain stimulation inhibits mossy fiber sprouting via 3′,5′-cyclic adenosine monophosphate/protein kinase A signaling pathway in a chronic epileptic monkey model

BackgroundAnterior thalamic nuclei (ATN) deep brain stimulation (DBS) is an effective method of controlling epilepsy, especially temporal lobe epilepsy. Mossy fiber sprouting (MFS) plays an indispensable role in the pathogenesis and progression of epilepsy, but the effect of ATN-DBS on MFS in the chronic stage of epilepsy and the potential underlying mechanisms are unknown. This study aimed to investigate the effect of ATN-DBS on MFS, as well as potential signaling pathways by a kainic acid (KA)-induced epileptic model.MethodsTwenty-four rhesus monkeys were randomly assigned to control, epilepsy (EP), EP-sham-DBS, and EP-DBS groups. KA was injected to establish the chronic epileptic model. The left ATN was implanted with a DBS lead and stimulated for 8 weeks. Enzyme-linked immunosorbent assay, Western blotting, and immunofluorescence staining were used to evaluate MFS and levels of potential molecular mediators in the hippocampus. One-way analysis of variance, followed by the Tukey post hoc correction, was used to analyze the statistical significance of differences among multiple groups.ResultsATN-DBS is found to significantly reduce seizure frequency in the chronic stage of epilepsy. The number of ectopic granule cells was reduced in monkeys that received ATN stimulation (P < 0.0001). Levels of 3′,5′-cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) in the hippocampus, together with Akt phosphorylation, were noticeably reduced in monkeys that received ATN stimulation (P = 0.0030 and P = 0.0001, respectively). ATN-DBS also significantly reduced MFS scores in the hippocampal dentate gyrus and CA3 sub-regions (all P < 0.0001).ConclusionATN-DBS is shown to down-regulate the cAMP/PKA signaling pathway and Akt phosphorylation and to reduce the number of ectopic granule cells, which may be associated with the reduced MFS in chronic epilepsy. The study provides further insights into the mechanism by which ATN-DBS reduces epileptic seizures.     

电针胃俞募配穴对胃扩张模型大鼠海马c-fos表达水平及神经细胞活动的影响

目的 探讨海马参与电针胃俞募配穴调节胃扩张模型大鼠胃运动的中枢机制。 方法 将40只7周龄SD大鼠随机分为模型组、胃俞组、中脘组、中脘+胃俞组、非经非穴组,每组8只。采用胃内球囊扩张法复制胃扩张模型。模型组不予针刺,其余各组进行电针干预,每日1次,每次20 min,连续干预7 d。采用压力换能器检测大鼠胃内压,用双导智能胃肠电图仪测定大鼠体表胃电。采用免疫荧光法检测大鼠海马c-fos的表达水平,采用微阵列电极技术记录大鼠海马神经细胞放电变化。结果 与模型组比较,中脘组、胃俞组及中脘＋胃俞组大鼠胃内压、胃电振幅均显著升高（P<0.05）,海马CA1区c-fos表达水平及海马CA1区神经细胞放电频率均显著增加（P<0.05）,但非经非穴组上述指标均无明显变化（P>0.05）。与中脘组、胃俞组比较,中脘+胃俞组大鼠胃内压、胃电振值均显著上升（P<0.05）,海马CA1区c-fos表达水平显著增加（P<0.05）,海马CA1区神经细胞放电频率显著增加（P<0.05）。结论 海马CA1区神经细胞参与电针胃俞募配穴对胃运动的调节机制。     

催产素减轻新生大鼠海马神经元缺氧缺血性损伤

目的:探讨催产素(oxytocin)对新生大鼠缺氧缺血性损伤后海马CA1区神经元的作用及机制。方法:采用氧糖剥夺(OGD)制备体外缺氧缺血模型,取8只7~10日龄新生大鼠的急性分离脑片(6~8片/只)随机分为4组,即对照组、OGD 20 min组、OGD 40 min组和OGD+oxytocin组,进行TO-PRO-3染色实验观察催产素对神经元的作用。另取20只新生大鼠脑片随机分为4组,分别是OGD组、OGD+oxytocin组、OGD+d VOT(催产素受体阻断剂)+oxytocin组和OGD+bicuculline(GABAA受体阻断剂)+oxytocin组,用全细胞膜片钳记录不同药物作用下海马神经元缺氧去极化的出现时间。结果:TO-PRO-3染色结果显示海马CA1区神经元死亡数量随着氧糖剥夺时间延长而增加,催产素能显著减少OGD所致的死亡神经元数目(P0.05)。全细胞膜片钳记录结果显示,催产素可使缺氧去极化时间显著延长;d VOT及bicuculline可以消除这种效应。结论:催产素能减轻新生大鼠海马CA1区神经元缺氧缺血性损伤,其机制可能是通过结合催产素受体,增强抑制性神经传递,从而产生神经保护作用。     

Functional implications of hippocampal volume and diffusivity in mild cognitive impairment

Hippocampal atrophy has been related to mild cognitive impairment (MCI) and early Alzheimer disease (AD), but the diagnostic significance of cross-sectionally determined hippocampal volumes is still ambiguous. Diffusion-Tensor-Imaging (DTI) in MCI patients revealed an association of microstructural changes in hippocampal areas with verbal memory decline. MRI volumetry and DTI were combined to investigate 18 MCI patients attending a memory clinic, and 18 carefully age- and gender-matched healthy controls. Neuropsychological testing, high resolution T1-weighted volume MRI scans, and DTI scans with regions-of-interest in hippocampal areas were applied. Left hippocampal volume was significantly lower (-11%, P = 0.02) in MCI patients than in control subjects. No significant differences were found for the right hippocampus (-4%). Mean diffusivity (MD) was significantly elevated in MCI patients vs. controls in left (+10%, P = 0.002) and right hippocampal areas (+13%, P = 0.02). Hippocampal volume and MD values were not significantly correlated. Combining left hippocampal volume and MD measures showed that lower left hippocampal volumes were associated with poor verbal memory performance particularly when co-occurring with high MD values. No comparable associations could be found regarding the right hippocampal formation and with respect to non-verbal memory function. The results demonstrate that microstructural abnormalities as revealed by DTI are very sensitive early indicators of hippocampal dysfunction. The combination of macro- and microstructural parameters in hippocampal areas could be promising in early detection of neurodegenerative processes.     

电刺激对海马表达Nogo-A蛋白的影响

目的 探讨慢性电刺激对大鼠海马表达Nogo=A蛋白表达的影响，以了解海马Nogo-A蛋白升高与癫痫发生的因果关系。方法 70只大鼠随机分为5组，即4个电刺激组，1个假电刺激组，分别电刺激1，3，6，9d，对海马进行免疫组织化学染色和蛋白印迹实验，检测海马表达Nogo-A蛋白的情况。结果 假电刺激组14只大鼠行为均无异常；电刺激1d与3d组大鼠亦未发生抽搐；电刺激6d组有3只发生抽搐，电刺激9d组在刺激6d时，有1只发生抽搐，刺激9d时有13只发生抽搐。同时，免疫组织化学实验发现，在电刺激3，6，9d后，海马Nogo-A蛋白表达量与假电刺激组相比均有显著升高（P〈0．05或P〈0．01），其升高趋势呈电刺激时间的依赖性（r=0．775），蛋白印迹实验结果基本相同。结论 海马Nogo-A蛋白表达的量与电刺激的时间呈正相关，而在发生癫痫之前大鼠海马Nogo-A蛋白表达已经升高。     

早期运动干预对脑缺血缺氧幼鼠海马区突触素蛋白表达的影响

目的 观察早期运动干预对缺血缺氧性脑损伤（HIBD）幼鼠大脑海马区神经元突触素(Syn)蛋白表达及尼氏体的变化,探讨HIBD早期运动干预的疗效机制。 方法 取3窝新生7d的幼鼠35只,按随机数字表法分为对照组（11只）、干预组（13只）和假手术组（11只）。制作新生Wistar大鼠幼鼠HIBD模型。干预组造模成功后7d开始早期运动干预,每天游泳10min,持续14d;对照组只造模不进行运动干预;假手术组只分离左侧颈总动脉但不结扎,不进行运动干预。采用免疫印迹（Western blot）法检测大脑海马区Syn蛋白的表达水平,以Syn和β带灰度值的比值表示syn蛋白相对表达量;采用尼氏染色方法依据形态学结果观察幼鼠海马区神经元尼氏体数量和细胞形态。 结果 对照组病灶侧海马组织Syn表达(0.447±0.141)较假手术组左侧海马组织Syn表达(1.027±0.035)显著降低(P<0.01)、海马区神经元尼氏体明显减少;干预组病灶侧海马区Syn表达(0.772±0.121)较对照组病灶侧海马组织Syn表达(0.447±0.141)明显升高(P<0.05)、海马区神经元尼氏体显著增多。 结论 早期运动干预可增强缺血缺氧幼鼠病灶侧海马区Syn蛋白的表达和增加神经元内尼氏小体数量。     

Age differences in neural correlates of route encoding and route recognition

Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18-29 years old) and 20 healthy old adults (53-78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that age-related navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region.