低氧预处理中Kv1.4和Kv4.2对海马和皮质的保护作用及其机制的研究

目的观察低氧预处理中Kv1.4和Kv4.2对海马和皮质的保护作用及机制。方法将35只雄性Wister大鼠随机分成低氧预处理组、严重低氧组和空白组。采用低压氧舱造模,低氧预处理组先置于低压氧舱4000米,每天2 h,连续3 d后再置于7000米,3 h;严重低氧组置于低压氧舱7000米,3 h;空白组不给予低氧处理。造模成功后于0 h、3 h、24 h 3个时间点,分别取材海马和皮质,采用Q-PCR的方法分别检测各组Wister大鼠海马和皮质Kv1.4和Kv4.2的基因表达,采用统计软件进行数据分析。结果 (1)低氧预处理组、严重低氧组大鼠海马中KV1.4和Kv4.2、大鼠皮质中Kv4.2的mRNA表达,在3 h、24 h均较空白组高,大鼠皮质中Kv1.4的mRNA表达在24 h高于空白组,有显著性差异(P<0.01),说明低氧时出现脑损害。(2)低氧预处理组大鼠海马和皮质中Kv1.4和Kv4.2的mRNA表达,与严重低氧组比较有下降,尤其是24 h明显降低,有显著性差异(P<0.01),说明低氧预处理过程可抑制Kv1.4和Kv4.2的mRNA过度表达,具有脑保护作用。结论低氧预处理对脑的保护作用可能与抑制Kv1.4和Kv4.2的mRNA表达有关。     

A型钾通道Kv1.4在致痫大鼠海马区的表达

目的 通过检测A型钾通道Kv1.4在戊四唑(PTZ)致痈大鼠海马CA1、CA3及齿状同区的表达变化,探讨A型钾通道与癫痫发病的关系.方法 SD大鼠40只,随机分为对照组、致痫后1h、24h、72h组,每组各10只.腹腔注射PTZ制备大鼠癫痫模型,应用免疫组化及Western Blot技术检测Kv1.4在各时间段海马CA1、CA3及齿状回区的蛋白表达.结果 致痫组大鼠海马区Kv1.4蛋白水平在致痫后1h、24h、72h 3个时间段均明显低于正常组(P<0.05);各致痫组之间Kv1.4蛋白水平均无明显差异(P>0.05).结论 (1)A型钾通道Kv1.4在SD大鼠海马中广泛分布.表达丰富,以轴突处最为明显.(2)大鼠癫痫模型海马区A型钾通道Kv1.4蛋白表达减少,提示Kv1.4的表达下调可能与癫痫的发病相关.     

蛇床子素对癫痫大鼠电压门控钾通道Kv1.2表达的影响

目的通过检测大鼠海马区钾通道Kv1.2蛋白表达的差异,探讨蛇床子素(osthole,OST)对海人酸(KA)致痫大鼠神经元的保护作用及其机制。方法 60只SD雄性大鼠随机分成空白对照组、模型组、OST组各20只。OST组首先给予OST灌胃,对照组、模型组给予等量的生理盐水灌胃,10d后,OST组与模型组通过颈内皮下注射KA致痫,对照组经颈内皮下注射等量的生理盐水。用免疫组化法和Western blot方法检测大鼠海马CA3区瞬时外向钾离子通道Kv1.2蛋白表达。结果模型组大鼠海马CA3区Kv1.2蛋白表达水平低于空白对照组(P<0.05);OST组大鼠海马CA3区Kv1.2蛋白表达水平高于模型组(P<0.05);且与空白对照组比较无明显差异(P>0.05)。结论大鼠海马CA3区神经元Kv1.2表达减少与KA导致大鼠痫样发作有关;OST对KA致痫大鼠神经元有保护作用,其作用的发挥可能与OST可增加海马CA3区神经元Kv1.2的表达有关。     

雷公藤内酯醇对癫痫大鼠电压门控钾通道kv1.1表达的影响

目的 探讨雷公藤内酯醇(TL)对癫痫大鼠神经的保护作用及其机制.方法 60只SD大鼠分成对照组、模型组、雷公藤组,每组各20只.雷公藤组大鼠腹腔注射TL(每日15μg/kg),模型组大鼠腹腔注射等量生理盐水,注射7d后,雷公藤组与模型组通过颈内皮下注射海人酸(KA)致痫,对照组则颈内皮下注射等量的生理盐水.用免疫组化和Western blot方法检测大鼠海马CA3区瞬时外向钾离子通道kv1.1蛋白表达.结果 模型组大鼠海马CA3区kv1.1蛋白表达水平低于对照组(P＜0.05);雷公藤组海马CA3区kv1.1蛋白表达高于模型组(P＜0.05);雷公藤组与对照组大鼠kv1.1蛋白表达水平无明显差异(P＞0.05).结论 TL对KA致痫大鼠神经元有保护作用,其作用的发挥可能与TL可增加海马CA3区神经元kv1.1的表达有关.     

癫痫持续状态后大鼠海马区钾离子通道Kv1.3的表达研究

目的研究氯化锂-匹罗卡品致癫痫持续状态(status epilepticus,SE)后大鼠海马区钾离子通道Kv1.3的表达及分布变化,探讨钾离子通道Kv1.3与癫痫发作的相关性。方法 48只健康雄性sprague-dawley大鼠随机平分为实验组和对照组,每组继续随机分为6 h、1 d、2 d和3 d 4个观察时间点亚组(n=6)。通过大鼠脑电监测记录大鼠脑电变化情况,通过尼氏染色观察脑组织病理改变,采用免疫组织化学染色和Western-blot方法检测各时间点大鼠海马区Kv1.3的表达及分布变化。结果 (1)脑电监测:正常大鼠脑电图表现为波幅较均匀一致的α波,痫性发作后开始出现慢波、棘波,波幅、节律不规则,SE过程中表现为长程的棘波活动。(2)尼氏染色:SE后6 h未发现明显形态学及神经元数量改变;SE后1 d,海马区神经元结构松散,神经元数量减少;SE后2 d、3 d,海马区神经元进一步减少,且出现神经元肿胀、变形、尼氏小体减少甚至消失。(3)免疫组织化学染色和Western-blot检测:SE后2 d,Kv1.3在海马CA_3和CA_1区表达较对照组明显减少(P0.05)。SE后6 h、1 d、3 d,Kv1.3在海马CA_3和CA_1区表达较对照组无明显变化(P0.05)。SE后6 h、1 d、2 d、3 d,Kv1.3在海马DG区表达较对照组无明显差异(P0.05)。结论 Kv1.3的表达下调可能与癫痫发作相关。     

缺氧抑制脑动脉Kv2.1通道作用机制的研究

目的探讨缺氧对脑动脉Kv通道抑制作用的机制是否由内源性15-羟二十碳四烯酸(15-HETE)介导。方法选取健康Wistar大鼠,通过酶法分离培养脑动脉和颈内动脉平滑肌细胞,分为正常对照组、缺氧组和去甲二氢愈创木酸(NDGA)缺氧组,正常对照组平滑肌细胞常规培养48h、缺氧组在缺氧箱内培养48h、NDGA缺氧组加入50μmol/L的NDGA后在缺氧箱内培养48h,使用RT-PCR和Western blotting技术检测大鼠脑动脉和颈内动脉平滑肌细胞上Kv2.1通道mRNA及蛋白质的表达情况。结果缺氧可以抑制大鼠脑动脉和颈内动脉平滑肌细胞上Kv2.1通道的表达,缺氧组与正常对照组相比,Kv2.1通道mRNA及蛋白质的表达下调(P<0.05);采用NDGA抑制15-脂氧化酶(15-LOX)后,导致脑动脉和颈内动脉平滑肌细胞上Kv2.1通道的表达上调,NDGA可以保护缺氧对于Kv通道的抑制,NDGA缺氧组与缺氧组相比,Kv2.1通道mRNA及蛋白质的表达明显上调(P<0.05)。结论缺氧可能通过内源性15-HETE发挥对Kv通道的抑制作用,15-HETE可能是影响脑动脉张力的重要中介因素。     

钾通道Kv1.2与致痫大鼠发病相关性的研究

目的通过检测戊四唑(PTZ)致痫大鼠钾通道Kv1.2蛋白表达,探讨钾通道Kv1.2与癫痫发病的相关性。方法 40只SD大鼠分成实验组30只和正常对照组10只。实验组30只大鼠通过腹腔注射PTZ建立全身强直阵挛发作大鼠癫痫模型,取成功致痫鼠24只均分成3组,分别于致痫后3个时间段(1h、24h、48h)取脑组织。用免疫组化法和Western blot法检测大鼠钾通道Kv1.2蛋白。结果实验组大鼠海马区钾通道Kv1.2蛋白表达水平在致痫后3个时间段(1h、24h、48h)均明显低于对照组(P0.05)。实验组大鼠海马区钾通道Kv1.2蛋白表达水平在致痫后3个时间段(1h、24h、48h)之间无显著性差异(P0.05)。结论大鼠海马区钾通道Kv1.2表达的减少与全身强直阵挛发作大鼠癫痫发病密切相关。     

A型钾通道Kv4.1在戊四唑致痫大鼠海马区的表达

目的通过检测A型钾通道Kv4.1在戊四唑(PTZ)致痫大鼠海马CA1、CA3及齿状回区的表达变化,探讨A型钾通道在癫痫发病机制中的作用。方法 SD大鼠40只,随机分为正常组、致痫后1 h、24 h、72 h组。腹腔注射PTZ制备大鼠癫痫模型,应用免疫组化及Western Blot技术检测Kv4.1在各时间段海马CA1、CA3及齿状回区的蛋白表达情况。结果致痫组大鼠海马区Kv4.1蛋白表达水平在致痫后1 h、24 h、72 h三个时间段均明显高于正常组(P<0.05);各致痫组之间Kv4.1蛋白表达水平无明显差异(P>0.05)。结论大鼠癫痫模型海马区A型钾通道Kv4.1蛋白表达增多,Kv4.1的表达上调可能在癫痫的发生中起作用。     

雌激素调控瞬时外向钾通道对大鼠慢性颞叶癫发作的影响

目的探讨雌激素对大鼠慢性颞叶癫发作的影响及其与瞬时外向钾通道(kv4.2)之间的关系。方法 SD雌性大鼠随机分为正常对照组、去势对照组、正常致组、去势致组。应用毛果芸香碱诱导大鼠癫持续状态(SE),观察大鼠行为学变化。经4周后成为慢性颞叶癫大鼠。Western bolt方法检测大鼠海马瞬时外向钾通道Kv4.2蛋白表达水平。结果与正常致组比较,去势致组达到SE的潜伏期延长、死亡率降低,但差异无统计学意义(P0.05);去势致组的癫发作强度较正常致组轻,差异有统计学意义(P0.05)。去势致组和正常致组在SE 4周后海马Kv4.2均较正常对照组显著升高,均差异有统计学意义(P0.05和P0.01)。去势对照组和去势致组比较,均未见对Kv4.2蛋白表达产生影响,说明Kv4.2蛋白表达升高为癫发作所致。结论大鼠癫发作后Kv4.2表达增加、瞬时外向钾电流增强、神经冲动的发放频率减慢,可能是产生代偿性自我保护反应的结果;虽然去势雌性大鼠未对Kv4.2表达产生影响,但出现潜伏期延长和死亡率降低、发作强度降低的行为学趋势,提示低剂量雌激素可能存在对癫发作的保护作用。     

文拉法辛对抑郁症模型大鼠海马神经元细胞凋亡的影响

目的 探讨文拉法辛对抑郁症模型大鼠海马神经元细胞凋亡相关基因表达的影响.方法 将SD大鼠随机分为抑郁模型组、文拉法辛干预组和正常对照组.以慢性轻度不可预见性的应激结合孤养建立抑郁症动物模型,应激同时文拉法辛干预组给予文拉法辛(15mg/kg)、抑郁模型组给予蒸馏水灌胃干预.采用敞箱实验和糖水消耗实验观察大鼠行为改变.用逆转录聚合酶链反应(RT-PCR)检测海马神经元细胞凋亡相关基因Bax、Bel-xl mRNA表达情况.结果 抑郁模型组与正常对照组比较,抑郁模型组海马神经元细胞Bax mRNA表达升高[(1.97±0.79)vs(1.28 4±0.49),P<0.01],Bcl-xl mRNA表达降低[(1.06 4±0.42)vs(1.51±0.48),P<0.01];与抑郁模型组比较,文拉法辛干预组海马神经元细胞Bax mRNA表达降低[(1.61±0.68)vs(1.97±0.79),P<0.05],Bcl-xl mRNA表达升高[(1.39±0.51)vs(1.06±0.42),P<0.05].结论 抑郁症模型大鼠存在海马损害,而文拉法辛对Bax mRN和Bcl-xl mBNA的表达具有干预作用,这可能为文拉法辛对抑郁症海马损害具有保护作用的机制之一.     

Activation of the Akt/GSK3beta signaling pathway mediates survival of vulnerable hippocampal neurons after transient global cerebral ischemia in rats.

Recent studies have revealed that the phosphatidylinositol 3-kinase (PI3-K) pathway is involved in apoptotic cell death after experimental cerebral ischemia. The serine-threonine kinase, Akt, functions in the PI3-K pathway and prevents apoptosis by phosphorylation at Ser473 after a variety of cell death stimuli. After phosphorylation, activated Akt inactivates other apoptogenic factors, including glycogen synthase kinase-3beta (GSK3beta), thereby inhibiting cell death. However, the role of Akt/GSK3beta signaling in the delayed death of hippocampal neurons in the CA1 subregion after transient global cerebral ischemia (tGCI) has not been clarified. Transient global cerebral ischemia for 5 mins was induced by bilateral common carotid artery occlusion combined with hypotension. Western blot analysis showed a significant increase in phospho-Akt (Ser473) and phospho-GSK3beta (Ser9) in the hippocampal CA1 subregion after tGCI. Immunohistochemistry showed that expression of phospho-Akt (Ser473) and phospho-GSK3beta (Ser9) was markedly increased in the vulnerable CA1 subregion, but not in the ischemic-tolerant CA3 subregion. Double staining with phospho-GSK3beta (Ser9) and terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling showed different cellular distributions in the CA1 subregion 3 days after tGCI. Phosphorylation of Akt and GSK3beta was prevented by LY294002, a PI3-K inhibitor, which facilitated subsequent DNA fragmentation 3 days after tGCI. Moreover, transgenic rats that overexpress copper/zinc-superoxide dismutase, which is known to be neuroprotective against delayed hippocampal CA1 injury after tGCI, had enhanced and persistent phosphorylation of both Akt and GSK3beta after tGCI. These findings suggest that activation of the Akt/GSK3beta signaling pathway may mediate survival of vulnerable hippocampal CA1 neurons after tGCI.     

Transient expression of A-type K channel alpha subunits Kv4.2 and Kv4.3 in rat spinal neurons during development

A-type K(+) currents (I(A)s) have been detected from the ventral horn neurons in rat spinal cord during embryonic day (E) 14 to postnatal day (P) 8 but not in adulthood. It is not known which types of neurons and which A-type K(+) channel alpha subunits express the I(A)s and what the possible function might be. Here, we examined the expression of two A-type K(+) channel alpha subunits, Kv4.2 and Kv4.3, in rat spinal cord at various developmental stages by immunohistochemistry. We found a transient expression of Kv4.2 in somatic motoneurons during E13.5-P8 with a peak around E17.5, which coincides temporally with the natural selection of motoneurons. Transient expression of Kv4.2 and Kv4.3 was also observed in the intermediate gray (IG) interneurons. During E19.5-P14, some IG interneurons express Kv4.2, some express Kv4.3 and a subset co-express Kv4.2 and Kv4.3. Peak expression of Kv4.2 and Kv4.3 in the IG interneurons was detected around P1, which coincides temporally with the developmental selection of IG interneurons. In contrast to the I(A)-expressing subunits Kv4.2 and Kv4.3, a delayed-rectifier K(+) channel alpha subunit Kv1.6 is persistently expressed in somatic motoneurons and IG interneurons. Together, these data support the hypothesis that expression of I(A)s may protect I(A)-expressing somatic motoneurons, and possibly also IG interneurons, from naturally occurring cell death during developmental selection.     

Postconditioning mitigates cell death following oxygen and glucose deprivation in PC12 cells and forebrain reperfusion injury in rats

Postconditioning mitigates ischemia‐induced cellular damage via a modified reperfusion procedure. Mitochondrial permeability transition (MPT) is an important pathophysiological change in reperfusion injury. This study explores the role of MPT modulation underlying hypoxic postconditioning (HPoC) in PC12 cells and studies the neuroprotective effects of ischemic postconditioning (IPoC) on rats. Oxygen‐glucose deprivation (OGD) was performed for 10 hr on PC12 cells. HPoC was induced by three cycles of 10‐min reoxygenation/10‐min rehypoxia after OGD. The MPT inhibitor N‐methyl‐4‐isoleucine cyclosporine (NIM811) and the MPT inducer carboxyatractyloside (CATR) were administered to selective groups before OGD. Cellular death was evaluated by flow cytometry and Western blot analysis. JC‐1 fluorescence signal was used to estimate the mitochondrial membrane potential (△Ψ_m). Transient global cerebral ischemia (tGCI) was induced via the two‐vessel occlusion and hypotension method in male Sprague Dawley rats. IPoC was induced by three cycles of 10‐sec reperfusion/10‐sec reocclusion after index ischemia. HPoC and NIM811 administration attenuated cell death, cytochrome c release, and caspase‐3 activity and maintained △Ψ_m of PC12 cells after OGD. The addition of CATR negated the protection conferred by HPoC. IPoC reduced neuronal degeneration and cytochrome c release and cleaved caspase‐9 expression of hippocampal CA1 neurons in rats after tGCI. HPoC protected PC12 cells against OGD by modulating the MPT. IPoC attenuated degeneration of hippocampal neurons after cerebral ischemia. © 2014 Wiley Periodicals, Inc.     

Arachidonic acid potently inhibits both postsynaptic-type Kv4.2 and presynaptic-type Kv1.4 IA potassium channels

Arachidonic acid (AA) is a free fatty acid membrane‐permeable second messenger that is liberated from cell membranes via receptor‐ and Ca²⁺‐dependent events. We have shown previously that extremely low [AA]_i (1 pm ) inhibits the postsynaptic voltage‐gated K⁺ current (I_A) in hippocampal neurons. This inhibition is blocked by some antioxidants. The somatodendritic I_A is mediated by Kv4.2 gene products, whereas presynaptic I_A is mediated by Kv1.4 channel subunits. To address the interaction of AA with these α‐subunits we studied the modulation of A‐currents in human embryonic kidney 293 cells transfected with either Kv1.4 or Kv4.2 rat cDNA, using whole‐cell voltage‐clamp recording. For both currents 1 pm [AA]_i inhibited the conductance by > 50%. In addition, AA shifted the voltage dependence of inactivation by ?9 (Kv1.4) and +6 mV (Kv4.2), respectively. Intracellular co‐application of Trolox C (10 μm ), an antioxidant vitamin E derivative, only slowed the effects of AA on amplitude. Notably, Trolox C shifted the voltage dependence of activation of Kv1.4‐mediated I_A by ?32 mV. Extracellular Trolox for > 15 min inhibited the AA effects on I_A amplitudes as well as the effect of intracellular Trolox on the voltage dependence of activation of Kv1.4‐mediated I_A. Extracellular Trolox further shifted the voltage dependence of activation for Kv4.2 by +33 mV. In conclusion, the inhibition of maximal amplitude of Kv4.2 channels by AA can explain the inhibition of somatodendritic I_A in hippocampal neurons, whereas the negative shift in the voltage dependence of inactivation apparently depends on other neuronal channel subunits. Both AA and Trolox potently modulate Kv1.4 and Kv4.2 channel α‐subunits, thereby presumably tuning presynaptic transmitter release and postsynaptic somatodendritic excitability in synaptic transmission and plasticity.     

The importance of immunohistochemical analyses in evaluating the phenotype of Kv channel knockout mice

To gain insights into the phenotype of voltage-gated potassium (Kv)1.1 and Kv4.2 knockout mice, we used immunohistochemistry to analyze the expression of component principal or α subunits and auxiliary subunits of neuronal Kv channels in knockout mouse brains. Genetic ablation of the Kv1.1 α subunit did not result in compensatory changes in the expression levels or subcellular distribution of related ion channel subunits in hippocampal medial perforant path and mossy fiber nerve terminals, where high levels of Kv1.1 are normally expressed. Genetic ablation of the Kv4.2 α subunit did not result in altered neuronal cytoarchitecture of the hippocampus. Although Kv4.2 knockout mice did not exhibit compensatory changes in the expression levels or subcellular distribution of the related Kv4.3 α subunit, we found dramatic decreases in the cellular and subcellular expression of specific Kv channel interacting proteins (KChIPs) that reflected their degree of association and colocalization with Kv4.2 in wild-type mouse and rat brains. These studies highlight the insights that can be gained by performing detailed immunohistochemical analyses of Kv channel knockout mouse brains.