神经元活动控制胼胝体纤维投射模式的研究取得新进展

2007年10月17日,Journal of Neuroscience杂志在线发表了中科院上海生科院神经所丁玉强研究员课题组关于神经元活动控制胼胝体纤维投射模式的最新研究成果。 胼胝体是脑内最大的联合系统,由两侧大脑皮层锥体细胞发出的轴突集合而成,负责两侧大脑半球之间的信息交换。一个重要的问题是：从一侧大脑皮层发出的胼胝体纤维是以怎样的方式投射到对侧皮层？这种投射模式是受哪些因素调控的？     

金鱼再生的视神经在顶盖投射精确化的DiI顺行标记研究

本文用微量显微注射法,在金鱼视网膜的背侧用亲脂类荧光染料DiI标记少量神经节细胞,通过顺行标记研究了视神经再生过程中视网膜顶盖投射的精确化过程。在损伤视神经后的不同时期观察了再生视神经纤维在顶盖整装片上的分布。在再生早期它们以超出正常的途径由背腹两侧进入顶盖,广泛分布。但其中大部分仍分布于顶盖腹侧的靶区。在再生晚期通过精确化,重建如正常鱼一样精确的视网膜顶盖投射。这个精确化过程表现在以下三方面:(1)再生于顶盖错误区域的再生视神经纤维的消失;(2)再生早期视神经纤维主干上生长的侧部分支的消失;(3)到达靶区的再生视神经纤维形成重迭的终末分支。由以上结果推测,顶盖中可能存在两类不同的因子:一类是普通诱向因子,存在于整个顶盖中,它在再生早期引导再生的视神经纤维长入顶盖。另一类是神经营养因子,它具区域特异性,在再生晚期引导视神经纤维到达顶盖靶区,形成精确的视网膜顶盖投射。     

非鸣禽丘脑听区和内分泌下丘脑区神经通路的免疫组织化学研究

应用神经示踪物BDA(biotinylated dextran amine)和免疫组织化学方法对环鸽(streptopelia risoria)丘脑听区和下丘脑内分泌脑区间的神经通路进行了研究。结果发现,丘脑卵形核壳 (Ov shell)及周围区域存在丰富脑啡肽免疫反应神经元。丘脑卵形核尾侧(Ovp)有传出纤维直接投射至Ov壳和下丘脑腹内侧核(VMN)。卵形核壳周围和下丘脑内分泌脑区间的传出神经通路显示了丰富的脑啡肽阳性免疫反应细胞和终末标记,在下丘脑腹内侧核中亦存在大量脑腓肽终末标记。结果提示Ov周围的部分脑啡肽神经元发出的传出纤维可能参与了鸽丘脑听区向内分泌下丘脑区投射的神经通路。     

损毁丘脑腹内侧核对大鼠行为的影响

黑质(SN)-纹状体多巴胺(DA)能神经元系统在调节躯体运动方面起着重要作用;但这一作用的传出神经通路尚无定论。在大鼠,丘脑腹内侧核(VM)是基底神经节的传出投射之一,主要接受SN网状部(SNR的投射纤维。本实验观察电损毁VM后,腹腔注射去水吗啡对大鼠姿势与行为的影响,以探讨SN-纹状体DA能神经元系统与VM在调节躯体运动中的功能联系。1 材料与方法 实验采用Sprague-Dawley系雄性大鼠,体重为200～300g,分为对照组(n=10)和实验组(n=11)。在1％成巴比妥钠麻醉下,将动物固定于立     

植物性神经中的肽能纤维

植物性神经是指支配心脏、腺体及内脏平滑肌的传出神经,分为交感神经和副交感神经。植物性神经的一个重要特点就是由二级神经元组成,节前神经元的胞体位于各自相应的中枢,发出节前神经纤维到达神经节。节后神经元的胞体位于神经节,发出的节后神经纤维直达所支配的效应器。植物性神经节前纤维末     

双斑蟋触角传入神经纤维在脑内投射分布研究

目的:研究昆虫触角感受器传入神经末梢在脑内投射的空间布局,揭示触角感觉信息传入的神经结构.方法:使用氯化镍神经元示踪标记技术,对双斑蟋触角感受嚣传入神经纤维进行可视化标记,观察研究触角传入神经末梢在脑内的走行形态及分布规律.结果:双斑蟋触角感受器传入神经纤维进入中脑后大量的神经末梢终止在同侧的触角叶和触角机械感觉运动中枢,部分神经纤维向前走行,其神经末梢终止在前脑,还有部分神经纤维向后下行,经同侧神经索,其神经末梢终止在食道下神经节.结论:双斑蟋触角感受器传入神经纤维进入脑后主要投射到触角叶和触角机械感觉运动中枢,少部分投射到前脑和食道下神经节.这种多重投射模式可能在双斑蟋嗅觉信息传递整合、触角运动调节、味觉和摄食活动等方面发挥重要作用.     

Bmal1对小鼠胚胎期皮层神经元放射状迁移和轴突投射的影响

大脑皮层的发育是脑结构形成与功能建立的重要基础,在此过程中,皮层神经元放射状迁移及胼胝体区的轴突投射是必不可少的关键环节,该环节受基因转录的调控,但相关的分子机制目前仍不明确。转录因子BMAL1 (brain and muscle Arnt-like protein1)是体内重要的生物钟节律因子之一,最新研究发现其还参与调节海马神经祖细胞增殖,提示其与神经发育存在潜在的相关性。为明确Bmal1基因在大脑皮层发育中的具体作用,本研究首先通过RT-PCR和Real-timePCR检测Bmal1基因在神经系统中的表达情况。结果表明,Bmal1基因在神经系统中表达丰富,并且在发育期的大脑内呈现特定的表达规律:在胚胎后期和出生后早期脑内表达水平相对较高,以出生后第3 d为高峰。进一步通过联合使用小鼠子宫内胚胎电转和RNAi干扰方法敲减脑内神经元中Bmal1的表达水平,结果发现胚胎期皮层神经元的放射状迁移发生了延迟,延迟程度与RNAi的敲减效率呈正相关,存在一定的基因剂量-效应关系。进一步观察发现,在胚胎期脑内神经元中降低Bmal1表达水平以后,胼胝体轴突向对侧大脑半球的投射也出现了明显的缺陷。上述研究结果表明,BMAL1是大脑皮层神经元的放射状迁移以及轴突投射发育过程中的一个重要的调控分子,为从转录因子角度深入理解大脑皮层发育的分子调节机制和寻找调控靶点提供了新的线索。     

THE IMMUNOHISTOCHEMICAL STUDIES OF PROJECTIONS LINKING THE AUDITORY THALAMUS AND NEUROSE- CRETORY HYPOTHALAMUS IN THE BRAIN OF NON - SONGBIRD

应用神经示踪物ＢＤＡ（ｂｉｏｔｉｎｙｌａｔｅｄｄｅｘｔｒａｎａｍｉｎｅ）和免疫组织化学方法对环鸽（ｓｔｒｅｐｔｏｐｅｌｉａｒｉｓｏｒｉａ）丘脑听区和下丘脑内分泌脑区间的神经通路进行了研究。结果发现,丘脑卵形核壳（Ｏｖｓｈｅｌ）及周围区域存在丰富脑啡肽免疫反应神经元。丘脑卵形核尾侧（Ｏｖｐ）有传出纤维直接投射至Ｏｖ壳和下丘脑腹内侧核（ＶＭＮ）。卵形核壳周围和下丘脑内分泌脑区间的传出神经通路显示了丰富的脑啡肽阳性免疫反应细胞和终末标记,在下丘脑腹内侧核中亦存在大量脑腓肽终末标记。结果提示Ｏｖ周围的部分脑啡肽神经元发出的传出纤维可能参与了鸽丘脑听区向内分泌下丘脑区投射的神经通路。     

大鼠中脑、内脏和躯体传入在旁巨细胞外侧核神经元的聚合

用细胞外记录的方法观察大鼠巨细胞旁外侧核（ＰＧＬ）对刺激中脑导水管周围背侧部（ｄＰＡＧ）及腹外侧部（ｖＰＡＧ）、腓深神经（ＤＰＮ）、正中神经（ＭＮ）和内脏大神经（ＧＳＰＬ）的反应。这些神经元不仅对某一处刺激部位起反应,而且倾向于对其它任一刺激部位也起反应。８９％（７３／８２）的神经元接受两处或两处以上来源的汇聚投射。６０％（２１／３５）的神经元由于具有压力敏感性,并且其下行投射到脊髓的轴突具有慢的     

视神经是真正的神经吗?

神经由神经纤维组成,位于神经系统的周围部,神经纤维的外面包以神经内膜,许多条神经纤维集合成神经束,神经束外面包以神经束膜,许多神经束集合成神经,神经外面包以神经外膜. 视神经由视网膜内节细胞轴突构成.视网膜分为三层细胞.第一层为视杆细胞和视锥细胞,二层为双极细胞,第三层为节细胞.从其结构组成和功能上看,视杆细胞和视锥细胞只是光感受器细胞,双极细胞和节细胞才是真正的神经元.节细胞的轴突组成视神经. 从胚胎学角度看神经系统的发生:视神经来自脑泡,在胚胎发育第四周,前脑泡的腹     

5-HYDROXYTRYPTAMINE, HISTAMINE AND N-ACETYLHISTAMINE IN THE NERVOUS SYSTEM OF DOSIDICUS GIGAS

Abstract— The optic ganglia, cerebral ganglia and mantle nerve of the squid Dosidicus gigas were examined for possible amines. Histamine was detected in all three tissues. The optic ganglia were also found to contain 5-HT and N -acetylhistamine, an infrequently found derivative of histamine.     

Structure of visual pathways in the nervous system of fresh water pulmonary molluscs

The central nervous system of freshwater pulmonary molluscs Lymnaea stagnalis and Planorbarins corneus was stained by the method of neurobiotin retrograde transport along optic nerve fibers. In the animals of both species, bodies and fibers of stained neurons are found in all ganglia except for the buccal ones. Afferent fibers of the optic nerve form a dense sensor neuropil located in a small volume of cerebral ganglia. Characteristic groups of neurons sending their processes into optic nerves both of ipsi- and of contralateral half of the body are described. Revealed among them are neurons of visceral and parietal ganglia, which simultaneously innervate both eyes as well as give projections into peripheral nerves. It is suggested that these neurons can perform function of integration of sensor signals and, on its base, regulate photosensitivity of retina as well as activity of peripheral organs. There is established the presence of bilateral connections of the mollusc eye with cells of pedal ganglia and statocysts, which seems to be the structural basis of manifestation of the known behavior forms associated with stimulation of visual inputs of the studied gastropod molluscs.     

Neurofilament phosphorylation in development. A sign of axonal maturation?

Monoclonal antibodies to the 200K neurofilament (NF) protein selectively decorated axons in tissue sections. Dilution of the antibodies in phosphate buffer and digestion with phosphatase abolished the stain. With conventional monoclonal and polyclonal NF antibodies, i.e. antibodies decorating NF regardless of their location (axons, perikarya and dendrites), the staining was not affected by this treatment. With all antibodies, axon-specific and conventional, the staining was abolished by trypsin digestion. Subsequent digestion with phosphatase did not restore the staining. Compared with conventional NF antibodies, staining with axon-specific anti-NF 200K was a late phenomenon in chick embryo development. NF 200K immunoreactivity was first observed in peripheral nerves and in the anterior columns of the spinal cord on day 10. Sensory ganglia and optic nerve fibers were negative. With conventional NF antibodies these structures were stained on days 4 and 5, respectively. In the following days of development the study was confined to the retina, optic nerves, cranial peripheral nerves and sensory ganglia. Up to day 16, bundles of thin peripheral nerve fibers, strongly decorated by conventional NF antibodies, did not stain with anti-NF 200K in double labelling experiments. Nerve bundles emerging from the ganglia were also negative, although some thick nerve fibers within the ganglia were stained. NF 200K immunoreactivity was first observed on day 17 in the optic nerve and in the layer of optic nerve fibers. At this time, staining was confined to the bundle emerging from the temporal side of the retina. In newborn chicken, only few fibers stained with anti-NF 200K in the nasal bundle, while the temporal bundle was well stained. It is suggested that the NF 200K antibodies reacted with a phosphorylated epitope in the axon, and that NF phosphorylation is a late event in ontogenesis probably related to axonal maturation.     

Neuronal pathways of three neurosecretory cells from the lateral lobes in Helisoma (Mollusca): innervation of the dorsal body

The neurite distribution of three large neurosecretory cells, namely one canopy cell and two lateral-lobe cells from each lateral lobe of the cerebral ganglia in Helisoma duryi were studied by thick and thin plastic serial sections. These cells from only the right lateral lobe innervate the dorsal body. Neurites from the canopy cell innervate the cell-bodies whereas those from the lateral-lobe cells innervate the cell-processes of the dorsal body. Neurosecretory granules from these neurites are released at their sites of innervation. The neurites of the optic nerve form synapses with lateral-lobe cell(1), and synapse-like contacts with lateral-lobe cell(2) while a neurite of each canopy cell is found within its collateral optic nerve. Based on the anatomy of the lateral-lobe nerve cells and the optic nerve, it is argued that the stimulatory effect of long days on the dorsal body and on egg production is mediated through the lateral-lobe cells and the canopy cell.     

In vitro studies on the control of nerve fiber growth by the extracellular matrix of the nervous system

1. Cultured neurons from embryonic chick sympathetic ganglia or dorsal root ganglia grow nerve fibers extensively on simple substrata containing fibronectin, collagens (types I, III, IV), and especially laminin. 2. The same neurons cultured on substrata containing glycosaminoglycans grow poorly. Glycosaminoglycans (heparin) inhibit nerve fiber growth on fibronectin substrata. 3. Proteolytic fragments of fibronectin support nerve fiber growth only when the cell attachment region is intact. For example, a 105 kD fragment, encompassing the cell attachment region, supports growth when immobilized in a substratum, but a 93 kD subfragment, lacking the cell attachment region, is unable to support fiber growth. When it is added to the culture medium, the 105 kD fragment inhibits fiber growth on substrata containing native fibronectin. 4. In culture medium lacking NGF, DRG neurons extend nerve fibers only on laminin and not on fibronectin, collagen or polylysine. Studies with radioiodinated laminin indicate that laminin binds with a relatively high affinity (kd approximately equal to 10(-9) M) to DRG neurons, and to a variety of other neural cells (NG108 cells, PC12 cells, rat astrocytes, chick optic lobe cells). We have isolated a membrane protein (67 kD) by affinity chromatography on laminin columns and are characterizing this putative laminin receptor. 5. Dissociated DRG neurons or ganglionic explants cultured on complex substrata consisting of tissue sections of CNS or PNS tissues extend nerve fibers onto the PNS (adult rat sciatic nerve) but not CNS (adult rat optic nerve) substrata. Other tissue substrata which support fiber growth in vivo (embryonic rat spinal cord, goldfish optic nerve) support growth in culture. While substrata from adult CNS, which support meager regeneration in vivo (adult rat spinal cord) support little fiber growth in culture. 6. Ganglionic explants cultured in a narrow space between a section of rat sciatic nerve and optic nerve grow preferentially onto the sciatic nerve suggesting that diffusible growth factors are not responsible for the differential growth on the two types of tissues. 7. Dissociated neurons adhere better to sections of sciatic nerve than optic nerve. Laminin, rather than fibronectin or heparan sulfate proteoglycan, is most consistently identifiable by immunocytochemistry in tissues (sciatic nerve, embryonic spinal cord, goldfish optic nerve) which support nerve fiber growth. Taken together, these data suggest that ECM adhesive proteins are important determinants of nerve regeneration.     

Hyalomma dromedarii (Acari: Ixodoidea: Ixodidae): Central and peripheral nervous system anatomy

TheHyalommadromedarii central nervous system, the synganglion, is an integrated nerve mass concentrated around the esophagus and formed by fusion of a small anterodorsal supraesophageal part an a large posteroventral subesophageal part. The supraesophageal part consists of the protocerebrum including a pair of optic ganglia, a pair of cheliceral ganglia, a pair of pedipalpal ganglia, and the stomodeal pons. The subesophageal part includes four paired pedal ganglia and the complex opisthosomatic ganglion. The peripheral nervous system includes the following pairs of nerves: optic, cheliceral, pedipalpal, primary and accessory (histologically traced); also unpaired pharyngeal and recurrent nerves, four pairs of pedal nerve trunks, each with a hemal branch, and two pairs of opisthosomatic nerves. Each peripheral nerve is traced distally to the innervation site. The salivary glands are innervated anteriorly by branches of the pedipalpal nerve and medially by branches of the hemal nerves associated with the third pedal nerves.Reprint request should be sent to: Medical Zoology Department, NAMRU-3, Fleet Post Office, New York 09527, U.S.A.     

化学损毁交感神经后大鼠心内神经节生长抑素的变化

应用免疫组织化学和原位杂交方法研究了大鼠心内神经节细胞中SS的分布及其mRNA表达。结果发现,大鼠心内神经节中有SS－IR阳性神经纤维和细胞,心内神经部分细胞浆中有SSmRNA表达,表明大鼠心内神经节细胞有SS合成和贮存。用小剂量6－OH－DA选择性损毁心内交感神经纤维后,心内神经节中SS－IR阳性神经纤维和细胞的积分光密度均有不同程度增强,反映了心内交感神经和付交感神经的相互抑制作用。     

Structure of visual pathways in the nervous system of freshwater pulmonate molluscs

Central nervous system of freshwater pulmonate molluscs Lymnaea stagnalis and Planorbarius corneus was stained using retrograde transport of neurobiotin in the optic tract fibers. In both species, perikarya and fibers of the stained neurons are found in all ganglia except the buccal ones. Afferent fibers of the optic nerve form dense sensory neuropil located in relatively small volume of cerebral ganglia. Typical neuronal groups sending their processes into the optic nerves of ipsilateral and contralateral body halves are described. Among them, neurons of visceral and parietal ganglia innervating both eyes concurrently as well as sending projections into peripheral nerves are revealed. These neurons, supposedly, have a function to integrate sensory signals, which may be a basis for regulation of light sensitivity of retina and functioning of peripheral organs. Bilateral links of the molluscan eye with the pedal ganglia cells and statocysts are found, which is, likely, a structural basis of certain known behavioral patterns related to stimulation of visual inputs in the studied gastropod molluscs.     

Analysis of mutual circadian pacemaker coupling between the two eyes of Bulla

The eyes of Bulla, a marine snail, express a circadian rhythm in the frequency of optic nerve compound action potentials (CAPs). The two ocular pacemakers are mutually coupled, and their interaction can be observed in vitro. The evidence for mutual coupling, as demonstrated in the present experiments, was as follows: (1) When intact Bulla were placed into darkness for up to 72 days, the two pacemakers did not desynchronize. (2) The free-running period of the ocular rhythm in the intact system (24.4 hr) was longer than the free-running period of the rhythm recorded from isolated eyes (23.7 hr). (3) When the two ocular pacemakers were experimentally desynchronized in vitro, resynchronization occurred if the pacemakers were allowed to interact for 48 hr. The coupling signals are most likely the CAPs. These impulses are conducted through the central ganglia and emerge as efferent impulses in the opposite optic nerve. Ocular-derived efferent impulse activity affects spontaneous impulse production in the target eye and alters the waveform of the circadian rhythm. The coupling pathway mediating syncrhonization consists of the two optic nerves, the cerebral ganglia, and the cerebral commissure. The demonstration of coupling in vitro provides a new opportunity for studying the cellular mechanisms underlying mutual pacemaker entrainment.     

Levels of choline intermediates in the visual system structures and in peripheral nerve of the rat: Comparison with neural tissues of a lower vertebrate (Mustelus canis) and an invertebrate (Loligo pealei)

The levels of choline intermediate endogenous pools in structures of the visual system (retina, optic nerve, lateral geniculate body, superior colliculus) and in sciatic nerve of adult (4-month-old) and young (30-day-old) rats were measured. The amounts were also obtained from retina, optic nerve, optic tectum and cranio-spinal nerves of a primitive elasmobranch, the smooth dogfish Mustelus canis, and from related nervous structures (retina, optic lobe, fin nerve, stellar nerve and stellate ganglia) of a marine invertebrate, the squid Loligo pealei. In all regions of rat nervous system, the pool size of CDP-choline was much smaller than that of free choline, whereas GroPCho was present in a relatively higher content. The pool sizes of choline intermediates in 30- and 120-day-old rats were nearly the same. In nervous system regions of the dogfish and squid, the values followed the same general trend as observed for rat. Squid nervous tissues had the lowest choline and GroPCho contents. The rat retina showed the lowest glycerophosphorylcholine phosphodiesterase activity. The chemical studies described here confirm the basic similarity in the pattern of choline intermediate pool sizes among animal species widely different in phylogenetic position. The data highly reinforce the idea that the precursor role of choline and catabolic pathways for the maintenance of the PtdCho membraneous pool seem highly conserved during evolution.