快速老化小鼠海马神经元电压门控离子通道特点

目的：观察快速老化小鼠（Senescence-accelerated mouse,SAM)海马神经元的基本离子通道特点，并对抗快速老化亚系（SAM－resistance/1,SAMR1)与快速老化亚系（SAM－prone/8,SMAP8)的基本离子通道特点进行了比较，探讨了离子通道变化在衰老中的可能角度，方法：应用全细胞记录方式，观察并比较原代培养SAMR1和SAMP8海马神经元的电压门控离子通道及膜参数。结果：原代培养SAMR1和SAMP8海马神经元电压门控Na^2 通道电流（INa)和电压门控延迟整流K^ 通道电流（IK）的电学特点和幅度基本一致。SAMP8的电压门控Ca^2 通道电流（ICa)和瞬时外向K^ 通道电流（IA）的幅值则大于相同培养天数的SAMR1。经膜电容校正所得的ICa电流密度也表现出增大的变化规律。结论：SAMP8与SAMR1神经元间IA和ICa的差异可能与其神经系统变异而产生的学习记忆功能下降有关。     

8-oxo-G在快速老化小鼠SAMP8海马中表达的增龄性变化研究

目的观察8-氧鸟嘌呤核苷(8-oxo-G)在SAMP8品系快速老化小鼠海马不同区域的表达,以探讨其与SAMP8小鼠增龄性变化的关系。方法选用1、4、8、12月龄的快速老化小鼠SAMP8以及同龄抗快速老化小鼠SAMR1(对照组),每组各6只,采用免疫组化方法检测小鼠海马不同区域8-oxo-G的表达。结果8-oxo-G主要在SAM小鼠海马神经元胞浆内表达。对照组SAMR1 1月龄小鼠海马CA1和CA3区8-oxo-G表达显著高于其他月龄组(P<0.05),4、8、12月龄小鼠间其表达差异无统计学意义(P>0.05);SAMP8 12月龄小鼠海马8-oxo-G的表达显著高于1、4、8月龄组(P<0.05);SAMP8和SAMR1小鼠之间比较,1、4月龄间差异无统计学意义(P>0.05),8、12月龄间差异有统计学意义(P<0.05)。结论SAMP8小鼠海马8-oxo-G的表达除1月龄外随月龄增加而增加,提示8-oxo-G的表达增加与SAMP8小鼠的快速老化相关,有可能为增龄,甚至AD的生物学标志。     

快速老化模型小鼠学习记忆行为及有关脑区单胺递质水平的增龄性变化

目的 研究快速老化模型小鼠(senescence accelerated mice，SAM)学习记忆能力及其大脑皮层、海马和下丘脑单胺递质含量的增龄性变化及它们之间的关系。方法 分别采用跳台实验和穿梭箱实验测定SAM的被动和主动回避反应能力，采用高效液相色谱电化学检测法测定脑内单胺递质的含量。结果 2月龄快速老化亚系SAM-prone/8(SAMP8)的被动和主动回避反应能力已较同龄抗快速老化亚系SAM-resistance／1(SAMR1)明显降低，且其主动回避反应能力随增龄进一步降低。同时，SAMP8大脑皮层、海马及下丘脑内单胺递质水平多明显高于同龄SAMR1，且随增龄明显增高。结论 SAMP8学习记忆能力的衰退可能与其相关脑区单胺递质的变化密切相关。     

8-氧鸟嘌呤脱氧核苷在快速老化小鼠SAMP8海马中表达的增龄性变化研究

目的观察8-氧鸟嘌呤脱氧核苷（8-oxo-7,8-dihydroguanine,8-oxo-dG）在快速老化小鼠SAMP8海马不同区域的表达,探讨其变化与SAMP8增龄的关系。方法选用1、4、8、12月龄快速老化小鼠SAMP8（每组各6只）,对照组为同龄抗快速老化小鼠SAMR1（每组各6只）,用免疫组化法检测海马不同区域内8-oxo—dG的表达水平。结果8-oxo-dG在海马不同区域均有表达,且主要在海马神经细胞胞核内表达。对照组SAMR1小鼠海马各区域8-oxo-dG的吸光度定量结果显示各月龄组间无统计学差异（P〉0．05）;1、4月龄组SAMP8小鼠海马各区域8-oxo-dG的吸光度定量结果与同龄匹配的SAMR1小鼠间无统计学差异（P〉0．05）;8、12月龄组SAMP8小鼠海马各区域8-oxo-dG的吸光度定量结果分别显著高于1月龄和4月龄组（P〈0．05）,也分别显著高于同龄SAMP1对照组（P〈0．05）。结论8-oxo-dG在SAMP8快速老化小鼠海马中的水平随增龄而显著增高。     

快速老化痴呆模型小鼠SAMP8学习记忆能力的增龄性变化

目的对快速老化痴呆模型小鼠SAMP8学习记忆能力的增龄性变化进行较系统的研究,为利用该模型进行其他研究提供实验依据。方法此实验选用1、4、8、12月龄的快速老化痴呆模型小鼠SAMP8,与同龄的正常老化小鼠SAMR1作对照,从老化度评分、避暗实验、Morris水迷宫实验和自主活动实验等方面观察了SAMP8小鼠学习记忆能力的增龄性变化。结果与对照组SAMR1相比,SAMP8小鼠随月龄增加老化度评分呈增高趋势,在8、12月龄的老化度评分值显著高于同龄对照组(P<0.05);避暗实验中,8、12月龄的SAMP8小鼠在电击24h后进入暗箱的潜伏期比同龄SAMR1小鼠显著缩短(P<0.05);Morris水迷宫实验中,1、4月龄SAMP8小鼠找到暗台的潜伏时间与同龄SAMR1小鼠相比差异无显著性,而8、12月龄SAMP8小鼠与同龄对照组相比,潜伏时间显著延长(P<0.05);从自主活动实验看,1、4、8月龄SAMP8小鼠单位时间内自主活动次数与同龄SAMR1小鼠相比无显著变化,而12月龄SAMP8小鼠与同龄对照组相比单位时间内自主活动次数显著减少(P<0.05)。结论SAMP8小鼠随月龄增长学习记忆能力逐渐减退;与同龄对照组相比,8、12月龄SAMP8小鼠出现明显衰老特征,表现出学习记忆能力明显低下,故可作为老化痴呆的动物模型用于痴呆有关研究。     

硬脑膜炎性刺激对三叉神经节小直径神经元电压门控钾电流的影响

目的通过炎性介质(IM)和降钙素基因相关肽(CGRP)诱发偏头痛反复发作,运用全细胞膜片钳的方法观察大鼠三叉神经节小直径神经元电压门控性钾电流的变化。方法雄性SD大鼠15只,分为空白组(不做任何干预)、生理盐水组和IM+CGRP组(大鼠硬脑膜上埋置PE-10管,连续7 d给予等量生理盐水和IM+CGRP)。用Von Frey毛测定大鼠眶周皮肤机械痛阈。在急性分离的三叉神经节小直径神经元上,通过全细胞膜片钳方法记录延迟外向钾电流(IK)和瞬时外向钾电流(IA)的变化。结果给药7 d后,IM+CGRP组大鼠的眶周机械痛阈明显降低,生理盐水组眶周机械痛阈无明显改变。生理盐水组三叉神经节神经元膜上总钾电流、IK、IA与空白组比较无明显差异;IM+CGRP组三叉神经节神经元膜上总钾电流、IK、IA与空白组和生理盐水组比较明显减小。结论 IM和CGRP诱发偏头痛反复发作模型大鼠的三叉神经节中急性分离神经元的IK和IA明显降低,提示电压门控性钾通道可能参与了外周机械痛阈的降低。     

大鼠背根神经节神经元S-型与O-型H+-门控离子通道外向电流研究

目的 在前期工作的基础上,从药理学敏感性的角度出发,初步探讨S-型与O-型H+-门控离子通道外向电流的离子成分及其药理学特性.方法 采用全细胞膜片钳技术记录急性分离的大鼠背根神经节神经元H+-门控离子通道电流,测定S-型与O-型离子通道外向电流的药理学特性,分析其成分组成.结果 高浓度的胞外K+、CsC1、BaCl2、4-氨基吡啶(4-AP)、四乙基溴化铵(TEABr)、CdCl2、阿米洛利等抑制S-型与O-型H+-门控离子通道外向电流,而Ca2+络合剂EGTA和高浓度的胞外Ca2+则增强该外向电流;胞外Na+浓度的变化对该外向电流无明显影响.结论 S-型和O-型H+-门控离子通道电流的外向电流离子成分可能为钙依赖性钾电流.     

增龄性脑血管相关改变对阿尔茨海默病模型小鼠SAMP8认知能力的影响

目的 探讨脑血流量、血脑屏障(BBB)通透性、脑葡萄糖跨膜转运蛋白表达情况随年龄增大对阿尔茨海默病(AD)模型小鼠SAMP8认知能力的影响. 方法 选择SAMP8小鼠及正常同源抗快速老化小鼠R1(SAMR1)各10只进行观察.采用Morris水迷宫测定小鼠的学习记忆能力,激光多普勒仪测定脑血流量,荧光分光光度计法测定BBB通透性,Western blotting测定葡萄糖转运蛋白(GLUT)1和3的表达. 结果 与SAMR1相比,SAMP8的认知能力早在4月龄时即已出现明显损伤,表现为思维僵化、学习过程减慢.随着年龄增大,SAMP8脑血流明显下降,BBB渗漏更为严重,皮层和海马的GLUT1和GLUT3表达也有不同程度地改变.脑血流、BBB完整性、GLUT1和GLUT3表达受年龄和品系影响明显,并与认知能力高度相关. 结论 衰老及缺血引起的血管损伤、能量供给不足是造成AD神经元功能异常及导致认知障碍的主要原因.     

第三讲 电压门控离子通道

在所有可兴奋细胞的细胞膜上都有许多蛋白通道。这些通道打开时 ,允许各种离子通过。其中 ,有些通道的打开由跨膜电压控制 ,称为电压门控离子通道。它们的特点是对某一种离子有特别高的通透性 ,根据离子通透的选择性可鉴别与区分离子通道。神经细胞中第一个被识别的电压门控离子通道是钠通道 (VDSC)和钾通道 (VDKC) ,它们决定着膜动作电位的变化。 Alan Hidgkin和 Andrew Huxley应用电压钳 (Voltageclamping)并结合药理学技术在枪鸟贼轴突上首先研究了钠通道和钾通道 ,证明动作电位由早期流入细胞的钠电流和晚期流出的钾电流组成。钠…     

新型FKBPs配体HD5-6对SAMP8小鼠的抗老化研究

目的观察FKBPs(FK506 blinding proteins)配体噻嗪酰胺衍生物(HD5-6)对SAMP8快速老化小鼠学习记忆能力和海马神经元的影响,以及对SAMP8小鼠海马神经元基因表达谱的影响。方法选用10月龄快速老化的SAMP8小鼠20只,随机分为痴呆组、HD5-6组;另选10月龄正常老化的SAMR1小鼠10只作为正常对照组。各组分别腹腔注射药物35 d,并于29 d采用Morris水迷宫实验评价各组小鼠学习记忆能力的变化。HE染色观察海马区神经元形态;TUNEL观察海马神经元凋亡情况,用基因芯片技术检测HD5-6组和痴呆组小鼠海马神经元基因表达谱的变化差异。结果与正常对照组相比,痴呆组在定位航行实验中表现出明显的学习记忆障碍,逃避潜伏期显著延长(P0.05),HD5-6组自3 d开始逃避潜伏期比痴呆组明显缩短(P0.05);空间探索实验中HD5-6组跨平台次数、原平台象限停留时间明显多于痴呆组(P0.05)。与正常对照组相比,痴呆组海马区神经元数量明显减少,细胞排列紊乱,大量的神经元细胞核固缩,深染、坏死,其神经元凋亡指数(51.73±4.48)%明显高于正常对照组(28.02±11.25)%(P0.05),HD5-6干预的SAMP8小鼠海马区神经元病理改变明显改善,海马神经元凋亡指数(20.47±2.25)%明显降低(P0.01)。HD5-6组与痴呆组海马神经元基因表达谱相比,表达差异在2倍以上的基因有118条,表达上调的为9条,表达下调的为109条。其中有功能的mRNA中,表达上调的有4条,表达下调的有21条。结论 HD5-6能够改善快速老化小鼠SAMP8的学习记忆能力和海马神经元病理改变,并可能通过对基因表达谱产生影响而发挥明显的抗衰老作用。     

Denervation study of synapses of organ of corti of old world monkeys

Fine structural characteristics of synapses in the spiral organ of Corti were examined, with reference to differences between inner and outer haircell systems, and to location of neurons of origin of efferent axons. Surgical interruption of crossed olivocochlear bundle, of vestibular nerve, of facial nerve, and excision of superior cervical ganglia were used to determine the pathways of efferent axons. Interruption of the vestibular nerve near the brainstem results in degeneration of all efferent terminals on outer hair cells. Mid-line lesions at, and caudal to, the facial colliculus result in degeneration of about half of these efferent terminals. Efferent synaptic bulbs to the inner hair-cell system are small, of the order of one micron, and form type 2 junctions with afferent dendrites. They tend to have more large dense-core vesicles (about 80 nm) than the large efferent terminals of the outer hair-cell system, and appear to be the terminals of axons in the habenula perforata, which exhibit varicosities laden with large dense core vesicles. The varicosities are unaffected by excision of the superior cervical ganglia. So far as our material can reveal, it appears that the varicosities in the habenula perforata do not survive vestibular root interruption, nor do the efferent processes in the internal spiral bundle or at the base of inner hair cells. Most interestingly, the afferent processes of the inner hair-cell system, as identified for example by their relation to pre-synaptic bodies in the inner hair cells, are subject to a trans-synaptic reaction after severance of the vestibular root. They undergo a dramatic cytological transformation, characterized by increase of volume, engorgement with microtubules, microfilaments, microvesicles of various sizes, and clusters of lysosomes. Thus, both the efferent and afferent terminals of the inner hair-cell system show marked cytological differences from the corresponding terminals of the outer hair cell system.     

Mechanism of action of tubocurarine on nicotinic cholinoreceptors of neurons of the sympathetic ganglia of rats

Tubocurarine (Tc) effect on membrane currents elicited by acetylcholine (ACh) was studied in isolated superior cervical ganglion neurons of rat using patch-clamp method in the whole-cell recording mode. The "use-dependent" block of ACh current by Tc was revealed in the experiments with ACh applications, indicating that Tc blocked the channels opened by ACh. Mean lifetime of Tc-open channel complex, tau, was found to be 9.8 +/- 0.5 s (n = 7) at -50 mV and 20-24 degrees C. tau exponentially increased with membrane hyperpolarization (e-fold change in tau corresponded to the membrane potential shift by 61 mV). Inhibition of the ACh-induced current by Tc (3-30 microM/1) was completely abolished by membrane depolarization to the level of 80-100 mV. Inhibition of ACh-induced current was augmented at increased ACh doses. It is concluded that the open channel block produced by Tc is likely to be the only mechanism for Tc action on nicotinic acetylcholine receptors in superior cervical ganglion neurons of rat.     

The effect of age of onset of PD on risk of dementia

Background Dementia occurs in the majority of patients with Parkinson’s disease (PD). Late onset of PD has been reported to be associated with a higher risk for dementia. However, age at onset (AAO) and age at baseline assessment are often correlated. The aim of this study was to explore whether AAO of PD symptoms is a risk factor for dementia independent of the general effect of age. Methods Two community-based studies of PD in New York (n = 281) and Rogaland county, Norway (n = 227) and two population-based groups of healthy elderly from New York (n = 180) and Odense, Denmark (n = 2414) were followed prospectively for 3–4 years and assessed for dementia according to DSM-IIIR. All PD and control cases underwent neurological examination and were followed with neurological and neuropsychological assessments. We used Cox proportional hazards regression based on three different time scales to explore the effect of AAO of PD on risk of dementia, adjusting for age at baseline and other demographic and clinical variables. Findings In both PD groups and in the pooled analyses, there was a significant effect of age at baseline assessment on the time to develop dementia, but there was no effect of AAO independent of age itself. Consistent with these results, there was no increased relative effect of age on the time to develop dementia in PD cases compared with controls. Interpretation This study shows that it is the general effect of age, rather than AAO that is associated with incident dementia in subjects with PD. Received in revised form: 22 December 2005     

Limits of deinstitutionalization--perspectives of relatives of psychiatric patients

After a hopeful beginning, the social process of the reintegration of those with severe mental illness has come to a standstill. I am led to wonder whether "the community" really wants to live together with people suffering from severe mental illness, and if so, how closely? As long as the medical treatment of mental illness provided by the general practitioners is fundamentally deficient, as they are not able to prescribe the necessary interventions--such as out-patient psychiatric nursing, and service providers in the out-patient sector are content with offering increasingly intensive forms of care for the less seriously ill at the cost of the Social Welfare System--the reintegration of those with serious mental illness remains an illusion--which is mainly to the benefit of providers of residential care in homes and hostels.