猫孤束核胶状质亚核的突触构筑学研究

用透射电镜对猫的孤束核胶状质亚核(SNG)的突触型式进行了观察,除看到已报导的轴—树突触、轴—体突触、树—树突触外,还发现该核内含有轴—轴突触及突触球等结构。SNG内轴—树突触最常见,而轴—体突触、轴—轴突触和树—树突触则较少。各类突触中的突触囊泡多为圆形清亮囊泡,而扁平清亮囊泡和大颗粒囊泡较少。扁平清亮囊泡多与圆形清亮囊泡共存于同一轴—轴突触终末内。轴—轴突触均为对称型突触,有时与树突或胞体相连形成轴—轴—树突触或轴—轴—体突触。突触球多为以树突和棘为中心的中心树突型突触球。此外在SNG内还观察到嵴突触,并联突触等连接形式。SNG内突触的复杂性表明传入冲动在该核中可能经过扩散、汇聚和突触前抑制等多种复杂的整合过程调节内脏活动。     

家兔脊髓腰骶部中间外侧核区的超微结构——神经纤维网和突触

本实验用家兔7只,取腰髓2～4和骶髓2～4节中间外侧核区,做超薄切片,电镜观察。此区的神经纤维网内含树突、轴突、轴突终末、终端树突、突触和突触球。胶质细胞的突起穿行其间。树突散在,形态和大小多变。轴突则常成束分布。突触连接以轴树和轴体突轴为多见,偶见轴轴突触。多数突触单独存在,部分形成以树突或轴突为中心的突触球。突触内的突触小泡有清亮的圆形、椭圆形、扁平形和不规则形,还有相当多见的大致密核心小泡和少数有衣小泡。依终末囊内突触小泡的形态和突触前后膜的对称与不对称,所见突触可分为三类:1.圆形小泡不对称型;2.扁平小泡对称型;3.其它中间类型。     

SP,CGRP,ENK样阳性纤维终末在猫骶髓后连合核内的分布特征及超微结构

本实验用免疫组化电镜技术对骶髓后连合核中SP祥、CGRP样、L-ENK样阳性终末进行了观察,结果表明:SP样阳性终末主要含圆形清亮小泡,间有少量颗粒囊泡,主要与中、小树突形成不对称型轴-树突触(93%);还可见到不对称型轴-体突触(5%);也可见到少量的轴-轴突触(2%),SP样阳性终末为突触后成分。CGRP样阳性终末以含圆形清亮小泡为主,有的终末内混有颗粒囊泡。大多数终末(89%)与树突构成轴-树突触,但以远侧树突为主;也有少数(6%)的CGRP样阳性终末与胞体形成轴-体突触;还观察到由阴性终末与CGRP样阳性终末构成的轴-轴突触。L-ENK样阳性终末以含圆形清亮小泡为主,有时可见散在的颗粒囊泡,多与中、小树突形成不对型轴-树突触(92%);也观察到轴-体突触(5%)和轴-轴突触(3%)。     

三叉神经尾侧脊束核内突触的亚显微结构

在电镜下观察家兔和小白鼠三叉神经尾侧脊束核,于突触前膜上可见突触活性点;在突触前,后膜上有致密物质堆积,尤以突触后膜显著,偶尔在后膜下方的胞浆面见有突触下致密小体。在突触裂之间可见突触间丝。突触小泡有圆形和椭圆形、透明与颗粒小泡之分。尾侧脊束核内有大量轴突终末与树突。树突又分Ⅰ型(无突触小泡)和Ⅱ型(有少量突触小泡)。该核内的突触类型多数为轴-树突触,其次为轴-体突触和轴-轴突触,还见有树-树突触;按照突触小泡形状区分该核突触,则有 S 型、F 型、S-F 型与 F-S 型。突触丝球出现率为20%。本文讨论了突触类型、突触丝球与突触小泡的机能意义。     

降钙素基因相关肽、甘丙肽免疫反应在大鼠臂旁外侧核分布的超微结构特征分析

应用免疫电镜包埋前染色技术对降钙素基因相关肽、甘丙肽免疫反应在大鼠臂旁外侧核分布的超微结构特征进行了研究。在臂旁外侧核腹外侧区中,常见降钙素基因相关肽阳性轴突终末与阴性树突及树突棘形成轴-树或轴-棘突触,大多为非对称型,少数为对称型;也可见阳性树突或阳性胞体与阴性轴突终末形成的轴-树或轴-体突触。阳性轴突终末含清亮小泡和致密核心小泡。臂旁外侧孩腹外侧部中甘丙肽阳性结构大多为阳性轴突终末,部分为阳性树突及阳性胞体。阳性树突常呈丛状分布于血管附近,阳性轴突常与阴性树突,阳性树突常与阴性轴突形成轴-树突触,大多为非对称型。臂旁外侧核腹外侧亚核的甘丙肽阳性结构分布基本与前者相似,但轴-树突触大多为对称型,而且一些阳性轴突与血管基膜紧贴。     

三叉神经尾侧脊束核内P物质纤维终末的超微结构

目的　进一步探讨三叉神经尾侧脊束核内SP免疫反应阳性纤维在感觉传递中的可能作用。方法　SP采用免疫细胞化学方法和电子显微镜方法 ,观察大鼠三叉神经尾侧脊束核内SP阳性标记纤维的超微结构和突触联系。结果　SP轴突终末分布于树突间 ,这些轴突终末含有大量的透明小泡、少量大致密芯小泡和线粒体。经过秋水仙素处理后 ,可见到SP免疫反应阳性树突。多数SP轴突终末与非标记树突 ,以及个别SP轴突终末与SP树突形成轴 树突触。含SP的突触复合体较为多见 ,为会聚型。其中可见SP轴突终末与中心的非标记树突形成GrayⅡ型轴 树突触 ;另有非标记的轴突终末与中心SP树突形成 (扁平小泡形 )F型轴 树突触。结论　三叉神经尾侧脊束核接受多种纤维传入 ,SP纤维只是多种传入纤维中的一种。形态学证明 ,在痛调制活动中 ,三叉神经尾侧脊束核内有SP纤维构成的突触后抑制类型 (GrayⅡ )突触参与。     

大鼠三叉神经脊束核尾侧亚核胶状质突触小球的超微结构

用透射电镜观察了大鼠三叉神经脊束核尾侧亚核胶状质突触小球的各种突起成分及突触联系。突触小球的中央轴突终未与周围两类 (一、二型)树突棘,树突干形成非对称的轴树突触。含突触小泡的二型树突棘、树突干与不含小泡的一型树突棘、树突干形成对称的树树突触,并与中央轴突终末形成树轴突触。周围轴突终末(P)与中央轴突终末形成对称的轴轴突触,并与小球内的树突形成对称的轴树突触。     

大白鼠下丘脑腹内侧核突触的电镜观察

本文报告大白鼠下丘脑腹内侧核内突触的类型和突触亚显微结构的形态特征。共观察了1005个突触,其中轴-树突触占96.6%;轴-体突触占2.8%;轴-轴突触占0.5%。在下丘脑腹内侧核中还观察到1例嵴突触,以往未见报道。嵴突触的突触后成分来自树突,呈杵指状突起。突触后膜明显增厚,具有突触下致密小体。两个内含圆形清亮小泡的轴突并列于嵴的两侧壁上,构成嵴突触。在轴-体、轴-树突触中尚观察到并联突触(包括突触复合体)、切线突触及串联突触等复杂的联接形式。本文对某些复合突触的机能也作了讨论。     

大鼠海马结构在空间辨别性学习记忆时的突触形态学观察

目的：探讨学习记忆活动是否可以引起大鼠海马结构发生突触可塑变化。方法：电子显微镜下对模型大鼠和对照大鼠的海马结构内突触复合体的形态进行了对比观察。结果：(1)模型大鼠海马CJ43区多形层内多为神经纤维，其中无髓纤维占多数，有髓纤维很少。在无髓纤维间见到形状不规则的轴突终末与周围的树突和树突棘分别形成轴—树突触和轴棘突触，后者多见。突触前膨大内充满圆形清亮、无核心的突触小泡和线粒体。突触后成分多为树突棘并在多处与突触前膜形成活性区，树突棘内见到棘器。(2)对照大鼠海马CA3区多形层内含有大量无髓纤维并见到较少的轴—树突触。该突触形状规则且活性带面积较小，突触后成分多为一个，突触小泡清亮、圆形无核心，偶见线粒体。(3)经Timm染色的两组大鼠海马CA3区多形层的超微结构特点是银颗粒仅沉积在苔藓纤维的髓鞘内和苔藓纤维的大终扣内，线粒体、树突干和树突棘内均无银颗粒。结论：正常生理活动和空间辨别性学习记忆活动均可引致大鼠海马CA3区多形层突触可塑性变化，但两者在形态上有所不同。     

大鼠中脑导水管周围灰质腹外侧区5-羟色胺样、P物质样和亮氨酸-脑啡肽样免疫反应阳性亚微结构的电镜观察

本文用免疫电镜技术研究了大鼠中脑导水管周围灰质腹外侧区内5-HT样、SP样和L-ENK样的免疫反应阳性亚微结构。5-HT样免疫反应阳性的胞体较多,常见5-HT样阳性树突与阴性轴突终末形成多为非对称性的轴-树突触;偶见阳性轴突终末与阴性树突以及阴性轴突终末与阳性胞体分别构成轴-树和轴-体突触.SP样阳性胞体数目较少,可见少量含多形性小泡的阴性轴突终末与之形成轴-体突触;由阴性轴突终末与阳性树突所形成的轴-树突触最常见;阳性轴突终末与阴性胞体和阳性树突分别构成轴-体突触和轴-树突触。L-ENK样阳性胞体数目也较少,L-ENK样阳性树突与阴性轴突终末所形成的轴-树突触最多见,可见L-ENK样阳性胞体与阴性轴突终末构成轴-体突触;偶见阳性轴突终末与阴性树突形成轴-树突触。上述各种突触均主要含圆形小泡,有时有少量扁平小泡、椭圆形小泡和颗粒囊泡。     

Ultrastructural study of cholecystokinin-like immunoreactive nerve terminals in the rat nucleus accumbens

The cholecystokinin (CCK)-like immunoreactive nerve terminals were studied in the caudal and medial parts of the rat nucleus accumbens (NA), using the indirect immunoperoxidase technique, at the electron microscopic level. In the labelled axon terminals the immunoprecipitate is localized inside large dense-cored vesicles which are occasionally present, and surrounds small and medium-sized, round, clear synaptic vesicles. The immunoreactive nerve terminals participate in synapses of both asymmetrical and symmetrical types containing mostly small synaptic vesicles. The asymmetrical synapses are much more numerous and mainly axo-spinous. The symmetrical synapses are less frequent and are axo-dendritic or axo-somatic.     

Catecholamine-containing axon terminals in the hypoglossal nucleus of the rat: an immuno-electronmicroscopic study

Summary A correlative light and electron microscopic investigation was undertaken to determine the morphology and distribution of catecholamine (CA)-containing axon terminals in the hypoglossal nucleus (XII) of the rat. This was accomplished immunocytochemically with antibody to tyrosine hydroxylase (TH). The major findings in this study were the following: 1) Immunoreactive profiles were found throughout XII and included unmyelinated axons, varicosities, axon terminals and dendrites; 2) Nonsynaptic immunoreactive profiles (preterminal axons, varicosities) were more frequently observed (55.2%) than synaptic profiles (43.5%); 3) CA-containing axon terminals ending on dendrites were more numerous (71.8%) than those synapsing on somata (25.4%) or nonlabeled axon terminals (2.7%); 4) The morphology of labeled axon terminals was variable. Axodendritic terminals typically contained numerous small, round agranular vesicles, a few large dense-core vesicles and were associated with either a symmetric or no synaptic specialization, axosomatic terminals were often associated with a presynaptic membrane thickening or a symmetric synaptic specialization and contained small, round and a few elliptical-shaped vesicles, while axoaxonic synapses formed asymmetric postsynaptic specializations; and 5) CA-positive dendritic processes were identified in XII. These findings confirm the CA innervation of XII, and suggest a complex, multifunctional role for CA in controlling oro-lingual motor behavior.     

A light and electron microscopic analysis of the convergent insular cortical and amygdaloid projections to the posterior lateral hypothalamus in the rat, with special reference to cardiovascular function

The synaptic organization between and among the insular cortex (IC) axons, central amygdaloid nucleus (ACe) axons and posterolateral hypothalamus (PLH) neurons was investigated in the rat using double anterograde tracing and anterograde tracing combined with postembedding immunogold analysis. After ipsilateral injections of biotinylated dextran amine (BDA) into the IC and Phaseolus vulgaris-leucoagglutinin (PHA-L) into the ACe, the conspicuous overlapping distribution of BDA-labeled axon terminals and PHA-L-labeled axon terminals was found in the PLH region just medial to the subthalamic nucleus ipsilateral to the injection sites. At the electron microscopic level, approximately two-thirds of the IC terminals made synapses with small-sized dendrites and the rest did with dendritic spines of the PLH neurons, whereas about 79%, 16% and 5% of the ACe terminals established synapses with small- to medium-sized dendrites, somata, and dendritic spines, respectively, of the PLH neurons. In addition, the IC axon terminals contained densely packed round clear vesicles and their synapses were of asymmetrical type. On the other hand, most of the ACe terminals contained not only pleomorphic clear vesicles but also dense-cored vesicles and their synapses were of symmetrical type although some ACe terminals contained densely packed round clear vesicles and formed asymmetrical synapses. Most of the postsynaptic elements received synaptic inputs from the IC or ACe terminals, and some of single postsynaptic elements received convergent synaptic inputs from both sets of terminals. Furthermore, almost all the ACe terminals were revealed to be immunoreactive for gamma-aminobutyric acid (GABA), by using the anterograde BDA tracing technique combined with immunohistochemistry for GABA. The present data suggest that single PLH neurons are under the excitatory influence of the IC and/or inhibitory influence of the ACe in the circuitry involved in the regulation of cardiovascular functions.     

大鼠延髓后角神经降压肽(NT)的亚细胞定位和胞吐释放

神经降压肽(NT)广泛分布于哺乳动物的中枢神经系统,具有明显的镇痛作用,为了探索其镇痛机理的形态学基础,本文应用电镜免疫组化技术,对大鼠延髓后角NT的超微结构和胞吐释放进行了研究。超微结构显示延髓后角浅层NT轴突终末形态多样,大小不一,含有圆形或多形性清亮小泡及数量不等的大颗粒小泡,它们主要与未标记的树突形成轴-树突触,其突触后成分有的还含有少量清亮小泡。NT免疫反应阳性树突可分为两类:一类主要含微管;另一类主要含大颗粒小泡,有的尚可见少量清亮小泡。这两类NT树突可成为未标记的含圆形小泡终末、多形性小泡终末以及突触小球中央轴突终末的突触后成分,提示后角浅层NT神经元可接受不同种类轴突终末(包括一级伤害性传入纤维)的传入(?)动,然后可能再通过一个抑制性中间神经元,抑制痛觉的传递。本文还观察到有少量NT终末内的大颗粒小泡靠近突触活性区处,而更多见它们沿非突触部位轴膜分布,并与其融合,形成胞吐。本文认为NT既可在突触活性区处又可能在非突触部位释放。     

Large dense-core vesicle exocytosis and membrane recycling in the mossy fibre synapses of the rabbit hippocampus during epileptiform seizures

Summary The ultrastructure of the hippocampal mossy fibre layer was studied in ultrathin sections and freeze-fracture preparations of rabbits under deep Nembutal anaesthesia, after recovery from ether anaesthesia, and 40 min after a single injection of methoxypyridoxine, that is, during the second generalized seizure discharge. The giant mossy fibre boutons contain two types of vesicles: evenly distributed, small round clear vesicles (50 nm) and a few scattered large dense-core vesicles (100 nm). In rare instances fusion of dense-core vesicles with the presynaptic membrane was observed. No differences in the morphology of the mossy fibre synapses were found between anaesthetized and unanaesthetized animals. During epileptiform seizures, however, the size and shape of clear and dense-core vesicles varied greatly. The active synaptic zones were covered with large, core-containing omega profiles or bumps and indentations. Only dense-core vesicles seem to undergo exocytosis. A fusion of clear vesicles with the presynaptic membrane was not observed.Various explanations for the fact that only dense-core vesicles seem to undergo exocytosis are discussed. The hypothesis is put forward that in the mossy fibre bouton two morphologically and functionally distinct populations of synaptic vesicles exist and that only one of them undergoes visible irreversible exocytosis, whereas the majority, that is, the small vesicles discharge their transmitter by reversible fusion.After MP injection features of membrane retrieval were also prominent. Frequently, at the borders of the active synaptic zones coated membrane convolutes of both pre- and postsynaptic membranes had invaded the terminals as well as the postsynaptic spine. Thus, in contrast to electrical stimulation, the self-sustained seizures allow energy-expensive processes such as extensive membrane internalization to take place during the interictal pauses.     

Synapses upon the axon origin of dorsal horn neurons in the rat spinal cord

Axon terminals synapsing with axon hillocks or origins of Golgi-impregnated and gold-toned neurons in the dorsal horn of the rat were shown in serial electron micrographs. Synapses occurred irrespective of the site (perikaryon or dendrite) and mode (with or without an axon hillock) of the axon origin. The synapsing axon terminals contained 3 populations of vesicles: pleomorphic and flattened synaptic vesicles and a combination of pleomorphic and dense-core vesicles. The membrane thickening in the axon-axon hillock synapses was of the symmetrical type.     

Neuronal and synaptic organization of the centromedian nucleus of the monkey thalamus: a quantitative ultrastructural study, with tract tracing and immunohistochemical observations

Summary The ultrastructure of the centromedian nucleus of the monkey thalamus was analysed qualitatively and quantitatively and projection neurons, local circuit neurons, and synaptic bouton populations identified. Projection neurons were mostly medium-sized, with oval-fusiform or polygonal perikarya, few primary dendrites, and frequent somatic spines; local circuit neurons were smaller. Four basic types of synaptic boutons were distinguished: (1) Small- to medium-sized boutons containing round vesicles (SR) and forming asymmetric contacts, identified as corticothalamic terminals. (2) Heterogeneous medium-sized boutons with asymmetric contacts and round vesicles, similar to the so-called large round (LR) boutons, which were in part of cortical origin. (3) Heterogeneous GAD-positive small- to medium-sized boutons, containing pleomorphic vesicles and forming symmetric contacts (F1 type), which included pallidothalamic terminals. (4) Presynaptic profiles represented by GAD-positive vesicle-containing dendrites of local circuit neurons. Complex synaptic arrangements, serial synapses and triads with LR and SR boutons engaging all parts of projection neuron dendrites and somata, were seen consistently, whereas classical glomeruli were infrequent. LR and SR boutons also established synapses on dendrites of local circuit neurons. F1 boutons established synapses on projection neuron somata, dendrites and initial axon segments. Compared to other previously studied motor-related thalamic nuclei, differences in synaptic coverage between proximal and distal projection neuron dendrites were less pronounced, and the density of synapses formed by local circuit dendrites on projection neuron dendrites was lower. Thus, compared to other thalamic nuclei, the overlap of different inputs was higher on monkey centromedian cells, and centromedian inhibitory circuits displayed a different organization.     

Synaptic circuitry in the retinorecipient layers of the optic tectum of the lamprey (Lampetra fluviatilis). A combined hodological, GABA and glutamate immunocytochemical study

The ultrastructure of the retinorecipient layers of the lamprey optic tectum was analysed using tract tracing techniques combined with GABA and glutamate immunocytochemistry. Two types of neurons were identified; a population of large GABA-immunonegative cells, and a population of smaller, highly GABA-immunoreactive interneurons, some of whose dendrites contain synaptic vesicles (DCSV). Five types of axon terminals were identified and divided into two major categories. The first of these are GABA-immunonegative, highly glutamate-immunoreactive, contain round synaptic vesicles, make asymmetrical synaptic contacts, and can in turn be divided into AT1 and AT2 terminals. The AT1 terminals are those of the retinotectal projection. The origin of the nonretinal AT2 terminals could not be determined. AT1 and AT2 terminals establish synaptic contacts with DCSV, with dendrites of the retinopetal neurons (DRN), and with conventional dendritic (D) profiles. The terminals of the second category are GABA-immunoreactive and can similarly be divided into AT3 and AT4 terminals. The AT3 terminals contain pleiomorphic synaptic vesicles and make symmetrical synaptic contacts for the most part with glutamate-immunoreactive D profiles. The AT4 terminals contain rounded synaptic vesicles and make asymmetrical synaptic contacts with DRN, with DCSV, and with D profiles. A fifth, rarely observed category of terminals (AT5) contain both clear synaptic vesicles and a large number of dense-core vesicles. Synaptic triads involving AT1, AT2 or AT4 terminals are rare. Our findings are compared to these of previous studies of the fine structure and immunochemical properties of the retinorecipient layers of the optic tectum or superior colliculus of Gnathostomes.     

Immunoelectron microscopic observations of hypothalamic TRH-containing neurons in rats

Summary Immunoreactive TRH-containing neurons and their synaptic associations were studied electron microscopically in the paraventricular nucleus (PVN) and dorsomedial nucleus (DMH) of the rat hypothalamus. In propylthiouracil (PTU)-treated rats, the immunoreactive cell bodies in the PVN appeared to be activated, showing a hypertrophic perikaryon, well developed Golgi bodies and numerous secretory granules. No such alterations were evident in the TRH neurons in the DMH. These findings suggest that the PVN-TRH neurons are involved in the hypothalamic-hypophysial-thyroid axis. Further, it was shown that unlabeled nerve terminals containing small and large clear vesicles make synaptic contacts with the TRH perikarya in the PVN. Thus it is likely that PVN-TRH neurons are regulated both by thyroid hormones and by other neuronal signals. In the DMH, unlabeled nerve terminals containing small and large clear vesicles, and immunoreactive terminals form synapses with TRH neurons. Thus the DMH-TRH neurons may be under dual neuronal control. It was further noted that in the DMH and PVN, TRH nerve terminals make synaptic contacts with other unlabeled neurons. It is evident that TRH acts as a neurotransmitter or neuromodulator, although the origin of TRH terminals should be elucidated.