大鼠视皮层神经元电生理和形态学特性在发育中的变化

为研究大鼠不同发育阶段视皮层神经元电的生理学与形态学特性,实验观察了神经元电生理和形态学特性的变化与年龄的同步化程度,探讨视皮层视觉依赖性突触的形成和重新分布的细胞内机制。应用脑片膜片钳全细胞记录技术和细胞内生物家标记相结合的方法,记录4—28d SD大鼠视皮层神经元的突触后电流(postsynaptic currents,PSCs)。共记录156个大鼠视皮层神经元,睁眼前与睁眼后组中无反应型细胞数量,多突触反应型细胞数量、细胞的输入阻抗有显著性差异。成功标记23例神经元,不同年龄的神经元的形态学成熟度不同。低输入阻抗神经元在形态学上属成熟型,高输入阻抗神经元属幼稚型。该结果表明,大鼠在发育过程中,视皮层神经元功能的成熟表现为在形觉刺激以及局部神经元网络的整合作用下的视觉依赖性突触的形成和重新分布。在视觉发育可塑性关键期内,视皮层神经元形态和电生理特性的变化与年龄的同步化程度大于皮层下结构。     

猫内侧膝状体年龄相关性形态学变化

目的比较青年猫和老年猫内侧膝状体神经元及S100蛋白与波形蛋白表达的年龄相关性变化。方法Nissl染色显示内侧膝状体结构及神经元,免疫组织化学方法示S100免疫反应阳性（S100-IRS100-immunoreactive）细胞及波形蛋白免疫反应阳性（Vimentin-IR Vimentin-immunoreactive）细胞。光镜下观察,利用图像分析软件进行图像采集分析。结果青年猫和老年猫内侧膝状体神经元数量及胞体直径无明显改变（P〉0.05）;与青年猫相比,老年猫内侧膝状体各分区中S100-IR细胞与Vimentin-IR细胞密度均显著增大,且免疫阳性反应强度增强（P〈0.01）,提示老年会导致内侧膝状体S100与波形蛋白表达显著增强。结论在衰老过程中,内侧膝状体处于静息和激活状态的星形胶质细胞均出现明显的增生,这对维持老年个体内侧膝状体神经元的正常形态和功能,从而延缓老年性听觉功能衰退可能具有重要作用。     

全细胞膜片钳研究离体小鼠内侧膝状体亚核神经元电生理特性

内侧膝状体(medial geniculate body,MGB)是听觉通路在丘脑的重要中继站,为了探究小鼠MGB亚核神经元的电生理特性,使用离体全细胞膜片钳技术记录到99个MGB神经元,其中腹侧核(ventral division of MGB,MGBv)神经元36个,背侧核(dorsal division of MGB,MGBd)神经元34个,内侧核(medial division of MGB,MGBm)神经元29个。结果表明,神经元对去极化电流的反应具有爆发型(bursting)(16.2%,16/99)和紧张型(tonic)(83.8%,83/99)两种发放模式,并且所有MGB神经元在超极化电流刺激结束后均有去极化反弹(rebound),而仅有少数神经元(17.2%,17/99)在超极化刺激过程中有超极化激活的内向电流(hyperpolarization-activated inward current,I_h)。此外,MGB各亚核神经元的静息膜电位(resting membrane potential,RMP)和激活阈值(active threshold)存在显著性差异(P0.05)。以上表明MGB各亚核的电生理特性存在差异,该结果有助于理解MGB各亚核在听觉信息处理中产生不同功能的原因。     

内侧膝状体解剖与生理学研究进展

内侧膝状体 (medialgeniculatebody ,MGB)是听觉系统在丘脑的重要接替核团。MGB的丘脑 皮层神经元 (thalamocorticalneuron)发出上行性纤维投射至听皮层 ,同时接受听皮层的皮层 丘脑神经元 (corticothalamicneuron)发出的下行性纤维投射。因此 ,听觉信息既受到MGB上行听觉通路的编码和整合 ,也接受皮层下行通路的调控。同时 ,MGB还参与声音定位、听觉可塑性等过程。本文总结近年MGB的解剖与生理学研究进展 ,着重叙述MGB与听皮层的纤维联系及其在听觉信息调控中的作用。     

猫外侧膝状体年龄相关性形态学变化

目的比较青年猫与老年猫外侧膝状体(lateral geniculate nucleus,LGN)神经元及γ-氨基丁酸(gama-aminobutyric acid,GABA)能神经元的年龄相关性变化,探讨老年个体视觉功能衰退的相关神经机理。方法Nissl染色示猫外侧膝状体分层结构(A、A1、C3层)及神经元,免疫组织化学法示GABA免疫阳性神经元。光镜下观察、拍照,Nissl染色切片测量外侧膝状体各层厚度、神经元胞体直径并计数神经元数量;免疫组化染色切片测量外侧膝状体各层中GABA阳性神经元胞体直径并计数GABA阳性神经元数量。结果青年猫及老年猫外侧膝状体各层厚度、神经元数量及胞体直径无明显改变(P>0.05);与青年猫相比,老年猫外侧膝状体各层中GABA阳性神经元数量及胞体直径均有不同程度的显著下降(P<0.01),且GABA免疫阳性反应减弱。结论在动物个体衰老进程中,外侧膝状体总体神经元保持相对稳定可能对老年个体维持视觉功能具有一定意义;老年个体外侧膝状体GABA能神经元对视觉信息传递及整合过程的抑制性调节功能削弱,可能是外侧膝状体水平上导致老年个体视觉功能衰退的原因之一。     

猫外侧膝状体周核神经元对正弦光栅刺激的反应特性

以正弦光栅研究了猫外侧膝状体周核(Perigeniculate Nuclells,PGN)神经元的空间频率和朝向调谐特性,以及空间总和性质.通常,PGN神经元空间频率调谐可分带通和低通二类.朝向特性可分为较宽范围朝向选择、无朝向选择和不规则朝向选择三类.用对比度翻转(ContrastReversal Grating(的光栅刺激时,少部分细胞存在零相位位置(Null Phase Positions),大多数呈现“二倍频”反应(Frequency Doubling Response).实验说明PGN神经元可能存在-X类型和-Y类型.     

发育中小鼠运动皮层锥体神经元电生理特性的变化

目的:研究小鼠生后发育过程中运动皮层锥体神经元电生理特性的变化。方法:选取出生后不同发育阶段的小鼠共计36只,随机分为1、2、3周龄组(1-, 2-, 3-Week)、1、2、3月龄组(1-, 2-, 3-Month)(n=6)。应用全细胞膜片钳及生物胞素细胞内标记技术区分锥体神经元与中间神经元,同时记录各组小鼠脑片运动皮层锥体神经元的被动膜特性、动作电位(AP)及兴奋性突触后电流(sEPSCs)。结果:与中间神经元相比,小鼠运动皮层锥体神经元的AP放电特征表现为规则放电(RS),放电频率较为缓慢。小鼠运动皮层锥体神经元的被动膜特性在出生后发育期间表现为：与1周龄组小鼠相比,2周龄组的静息膜电位(RMP)表现为显著超极化(P<0.01),2周后再无明显改变;1月龄组的膜输入阻抗(R_in)呈现显著下降的趋势(P<0.01),在1月龄后无明显变化;膜电容(Cm)无明显变化。AP在发育早期的变化表现为：与1周龄组小鼠相比,3周龄组AP阈电位绝对值和幅值显著增加(P<0.01),2周龄组AP半波宽显著降低(P<0.05),在此之后无显著变化。sEP...     

大鼠海马CA1区锥体神经元I_A和I_K在出生后早期的变化

大脑快速发育期(brain growth spurt,BGS)是神经元生长、突触连接的关键时期;电压门控性K+通道是维持细胞兴奋性和神经元间信息传递的关键通道。本文旨在探究BGS期内大鼠海马CA1区锥体神经元电压门控性K+通道电流及其通道动力学特性的变化,以期找出大鼠海马CA1区锥体神经元电压门控性K+通道发育的关键期。采用全细胞膜片钳技术,研究出生后0~4周大鼠海马CA1区脑片上的锥体神经元全细胞电压门控性K+通道电流及其通道动力学特性。结果显示:在测试电压为+90mV下,以出生后0周为参照,出生后1~4周的瞬时外向K+通道电流(IA)的最大电流密度的增幅分别为(16.14±0.51)%、(81.73±10.71)%、(106.72±5.29)%、(134.58±8.81)%(n=10,P<0.05);延迟整流K+通道电流(IK)的最大电流密度增幅分别为(16.75±3.88)%、(134.01±2.85)%、(180.56±8.49)%、(194.5±8.53)%(n=10,P<0.05),显示K+通道电流密度于1~2周增幅最大;IA的激活曲线向左移,半数激活电压随周龄增加逐渐减小,分别为14.67±0.75、13.46±0.64、8.39±0.87、4.60±0.96、0.54±0.92(mV,n=10,P<0.05);IK的激活曲线向左移,半数激活电压随周龄增加逐渐减小,分别为8.94±0.85、6.65±0.89、0.47±1.15、1.80±0.89、8.56±1.08(mV,n=10,P<0.05)。IA的失活曲线向左移,0周龄与1周龄之间的半数失活电压没有显著性差异,而出生后1~4周随周龄增加半数失活电压逐渐减小(P<0.05),分别为45.68±1.26、46.81±0.78、48.64±0.81、51.96±1.02、58.31±1.35(mV,n=10)。以上结果表明,随着鼠龄的增加,IA和IK电流密度逐渐增加,电压门控性K+通道半数激活、失活电压降低,尤其是出生后1周至2周变化明显,上述变化与海马神经元的逐渐发育成熟及其功能的完善有关。     

S100蛋白与GFAP在猫外侧膝状体表达的年龄相关性变化

目的 比较青年猫与老年猫外侧膝状体（lateral geniculate nucleus,LGN）星形胶质细胞（astrocyte,AS）中S100蛋白与胶质原纤维酸性蛋白（glial fibrillary acidic protein,GFAP）表达的年龄相关性变化,探讨导致相关变化的原因及其在动物视觉功能衰老中的意义。方法 免疫组织化学方法（SABC法）示S100蛋白阳性细胞及GFAP阳性细胞。光镜下观察、拍照,计数外侧膝状体各层中S100蛋白阳性细胞及GFAP阳性细胞数量。结果 与青年猫相比,老年猫外侧膝状体各层中S100蛋白与GFAP表达均有不同程度的显著增强（P〈0.01）。结论 动物视觉衰老进程中,外侧膝状体星形胶质细胞存在着明显的反应性胶质化（reactive gliosis）,这种胶质化与老年动物视觉功能之间关系将在文中讨论。     

经脂多糖(LPS)处理免疫应答大鼠离体脑片视上核神经元对细胞因子敏感性的变化

实验采用离体脑片全细胞膜片箝记录方法 ,观察了细胞因子白介素 1β(IL 1β)和IL 2对大鼠离体脑片视上核神经元膜电位及自发放电的影响 ,以期探明免疫应答大鼠视上核神经元对细胞因子敏感性的变化。结果显示 ,用 10 0U/mlIL 1β灌流脑片 ,正常对照的 (n =15 )和脂多糖 (lipopolysaccharideLPS)腹腔注射 9d的大鼠视上核神经元 (n =2 0 )超极化 ,同时伴有自发放电频率的下降 ;应用 10 0U/mlIL 2 ,大部分正常对照视上核神经元 (n =14)表现为超极化 ,自发放电减少 ,剩余部分 (n =3)变化不明显 ;在LPS免疫 9d大鼠离体脑片上的 45个视上核神经元中 ,10 0U/ml的IL 2使其中 19个表现为去极化并伴有自发放电频率增加 ,16个变化不明显 ,其余 10个表现为超极化伴放电频率下降。以上结果表明 ,在免疫应答中 ,视上核神经元对细胞因子IL 2的敏感性 ,在一定的程度上发生了改变 ,细胞因子IL 2可能参与了视上核神经元的功能调节 ,进而在免疫应答过程中发挥了调节作用。     

Changes of the caecal villi during postnatal development in rats

Summary The villi of the caecal mucosa in postnatal rats were studied using both scanning electron and light microscopy.On the day of birth, numerous villi of various sizes and shapes were present on the caecal mucosa. After the 5th day, the villi decreased very rapidly in length and in number. A strong constriction was observed at the basal region of the caecal villi. During postnatal days 5 9 the villi probably separated and disappeared from the caecal mucosa. No villi were observed in rats that were over 10 days of age.     

生物组织切片图像的计算机三维重建技术现状及其在植物体细胞胚发生中的应用

本文阐述了植物组织切片的三维计算机重建技术研究现状 ,分析了它在植物体细胞胚发生专题中的应用     

Effects of toxin II from the scorpion Androctonus australis Hector on sodium current in neuroblastoma cells and their modulation by oleic acid

The effects of toxin II (AaH II) isolated from the scorpion Androtonus australis Hector on sodium current in neuroblastoma X glioma NG 108-15 hybrid cells were analysed under patch clamp conditions in the whole cell configuration. AaH II (70 nM)_induced a maintained sodium current, as well as increasing both fast and slow inactivation time constants and the amplitude of the peak current. This latter effect occurred via a shift of the activation-voltage curve towards negative voltage values by about 9 mV. Oleic acid (5 M), which had no effect on I_Na under control conditions, decreased the AaH II-induced maintained current. It also reversed, or prevented the increase of the peak current induced by AaH II. However, it neither prevented nor modified the AaH II-induced increase in inactivation time constants. The binding of the toxin to its specific site and the number of binding sites for AaH II were not significantly modified by oleic acid. The oleic acid-induced effects could not be related to the activation of protein kinase C since PMA, a potent activator of this enzyme, did not produce oleic acid-like effects. From these results, it is concluded that AaH II has several independent effects on sodium channels, some of which could be modulated by the lipid environment of sodium channels in the membrane.     

Changes in brain amine levels associated with the morphological and behavioural development of the worker honeybee

Summary Changes in biogenic amine levels associated with the morphological and behavioural development of the worker honeybee are examined.A significant increase in amine levels in the head of the honeybee is associated with transition from the larval to pupal stage. Adult emergence is also accompanied by a significant increase in 5-HT levels in the brain, but no significant change in brain dopamine (DA) levels. NADA (N-acetyldopamine) levels increase during larval and pupal development, but in contrast to both DA and 5-HT, drop significantly during the transition from pupa to adult.Levels of DA in the brain of nectar and pollen forager bees, presumed to be among the oldest adults sampled, were found to be significantly higher than in nurses, undertakers or food storers. These results suggest that an age-dependent change in amine levels occurs in the brain of the worker bee. In the optic lobes, levels of DA and 5-HT were found to be significantly higher in pollen forager bees than in all other behavioural groups. Significant differences in amine levels in the optic lobes of nectar foragers and pollen foragers indicate that some differences in amine levels occur independent of worker age. The functional significance of differences in brain amine levels and whether or not biogenic amines play a direct role in the control of honeybee behaviour has yet to be established.Abbreviations DA dopamine - 5-HT 5-hydroxytryptamine or serotonin - NADA N-acetyldopamine     

Changes in the intracellular accumulation and distribution of metallothionein in rat liver and kidney during postnatal development

Metallothionein (MT) bound to zinc and copper was detected in high concentration in fetal and newborn rat livers by a cadmium saturation method. The levels of both hepatic zinc and MT remained high for the first 14 days after birth and decreased to adult levels by 24 days of age. There was a direct linear relationship between hepatic metallothionein and zinc concentrations during the first 31 days after birth. The ratio of MT to zinc levels also decreased with age suggesting a rapid degradation of MT during postnatal development. Immunohistochemical localization of MT by peroxidase-antiperoxidase technique, using a specific antibody to MT, showed intense intranuclear staining for MT in fetal and newborn rat liver which persisted until Day 9. The nuclear MT staining decreased with age; at 11 days it was equal both in nucleus and cytoplasm and at 14 days, MT was localized mainly in the cytoplasm, similar to adult rat liver pattern. The intranuclear localization of MT in neonates could be considered as a typical fetal-neonatal morphological pattern and its subsequent presence in the cytoplasm, an adult pattern.     

Changes in regional brain synaptosomal high affinity choline uptake during the development of hypertension in spontaneously hypertensive rats

The high-affinity uptake of choline (HAChU) by freshly prepared crude synaptosomal fractions was employed as relative measure of regional brain cholinergic activity. TheV _max for uptake as determined by the accumulation of a tracer amount of³H-choline in the presence of unlabeled choline (0.2–2 M) varied 6 fold depending upon the region examined (striatum>hypothalamus>medulla-pons). HAChU was hemicholinium-3-sensitive and linear at 37°C from 1 to 8 min in all brain regions. Respective brain synaptosomal fractions derived from adult (12 week old) spontaneously hypertensive (SH) rats and normotensive Wistar Kyoto (WK) rats revealed no difference in theV _max for HAChU from synaptosomes derived from the striatum of either strain. However, there was a significant increase in theV _max for HAChU measured from the medulla-pons of SH rats compared with WK rats. In older (22 weeks) rats, theV _max for HAChU was 78% greater than age-matched WK control rats. In addition, a highly significant correlation was found between resting systolic blood pressure and theV _max for HAChU both in the medulla-pons (r=0.76) and hypothalamus (r=0.48). That the increase in HAChU in SH rats was not a consequence of elevated pressure, was indicated by the lack of effect of prolonged i.v. infusion of pressor agents in normotensive rats on HAChU. These findings are consistent with a role for brain cholinergic neurons in the maintenance of hypertension in SH rats.     

Control of K+ conductance by cholecystokinin and Ca2+ in single pancreatic acinar cells studied by the patch-clamp technique

Summary The effect of cholecystokinin (CCK) and internal Ca²⁺ on outward K⁺ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 × 10^–10 M) applied to the bath evoked a marked increase in the outward K⁺ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca²⁺. When strongly buffered Ca²⁺-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca²⁺ concentration ([Ca²⁺] _i ) from 5 × 10^–10 M to 10^–7 and 5 × 10^–7 M mimicked the effect of CCK. It would appear therefore that CCK controls K⁺ conductance in the acinar cells via changes in the internal free ionized Ca²⁺ concentration.     

Physiological properties and response modulations of mushroom body feedback neurons during olfactory learning in the honeybee, Apis mellifera

Mushroom bodies are central brain structures and essentially involved in insect olfactory learning. Within the mushroom bodies γ-aminobutyric acid (GABA)-immunoreactive feedback neurons are the most prominent neuron group. The plasticity of inhibitory neural activity within the mushroom body was investigated by analyzing modulations of odor responses of feedback neurons during olfactory learning in vivo. In the honeybee, Apis mellifera, feedback neurons were intracellularly recorded at their neurites. They produced complex patterns of action potentials without experimental stimulation. Summating postsynaptic potentials indicate that their synaptic input region lies within the lobes. Odor and antennal sucrose stimuli evoked excitatory phasic-tonic responses. Individual neurons responded to various odors; responses of different neurons to the same odor were highly variable. Response modulations were determined by comparing odor responses of feedback neurons before and after one-trial olfactory conditioning or sensitisation. Shortly after pairing an odor stimulus with a sucrose reward, odor-induced spike activity of feedback neurons decreased. Repeated odor stimulations alone, equally spaced as in the conditioning experiment, did not affect the odor-induced excitation. A single sensitisation trial also did not alter odor responses. These findings indicate that the level of odor-induced inhibition within the mushroom bodies is specifically modulated by experience. Accepted: 9 September 1999