Synaptic organization of cortico-cortical connections from the primary visual cortex to the posteromedial lateral suprasylvian visual area in the cat

The synaptic organization of the projection from the cat striate visual cortex to the posteromedial lateral suprasylvian cortical area (PMLS) was examined. The anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) was iontophorectically delivered into area 17, and anterogradely labeled fibers were revealed in PMLS by means of an immunocytochemical detection method. Most axons and presumptive terminal swellings were found in layers III and IV. The neuronal elements (n = 190) that were postsynaptic to anterogradely labeled boutons were quantitatively analyzed. All anterogradely labeled cortico-cortical boutons (n = 182) established type 1 synapses. The results show that 83% of the postsynaptic targets were dendritic spines, probably belonging to pyramidal cells. Dendritic shafts constituted 17% of the targets. The dendritic shafts postsynaptic to cortico-cortical boutons were studied for the presence of gamma-aminobutyric acid (GABA) with a postembedding immunogold method. Most dendritic shafts (85%) that were tested were found to be GABA-positive, demonstrating that they originate from local inhibitory neurons. Taking into account that most postsynaptic targets were spines and extending the results of the immunocytochemical testing to the total population of postsynaptic dendrites, it was calculated that at least 14% of targets originated from GABA-positive cells. Thus cortico-cortical axons establish direct monosynpatic connections mainly with pyramidal and to a lesser extent with GABAergic nonpyramidal neurons in area PMLS, providing both feedforward excitation and feedforward inhibition to a visual associational area known to be involved in the processing of motion information. The results are consistent with previously demonstrated deficits in physiological properties of neurons in PMLS following removal of cortico-cortical afferents.     

Synaptic reorganization in the medial amygdaloid nucleus after lesion of the accessory olfactory bulb of adult rat. II. New synapse formation in the medial amygdaloid nucleus by fibers from the bed nucleus of the stria terminalis

The rearrangement of terminations from the bed nucleus of stria terminalis (BST) was examined in the medial amygdaloid nucleus (MAN) at 2 months following the lesion of the accessory olfactory bulb (AOB) using an electron microscopy and degeneration study. At 2 days following a BST lesion, the number of degenerating synapses was 0.7 ± 0.1 (mean±S.E.M.) per unit area (2500 μm² in the molecular layer, and 3/0 ± 0.3 in the cellular part. At 2 months after an AOB lesion, the degenerating synapses from the AOB had completely disappeared from the MAN. The BST was then lesioned at 2 months after the AOB lesion and, 2 days following this BST lesion, the degenerating synapses were counted in MAN. The numbers observed were 3.3 ± 0.6 per unit area in the molecular layer and 4.5 ± 0.4 in the cellular part. Therefore, the number of these degenerating synapses increased significantly within the molecular layer, though, in the cellular part the number of synapses was not significantly elevated over control. No differences in postsynaptic profiles (ratio of synapses on dendritic spine to dendritic shaft) were observed after the AOB lesion. These results indicate that the BST fibers formed new synapses in the molecular layer following the denervation of AOB fibers. The possibility of new synapse formation by other afferent fibers in addition to the AOB fibers is discussed as is the relationship between lesion induced synaptic reorganization and functional recovery after injury.     

Ultrastructure of the periaqueductal grey matter of the rat: an electron microscopical and horseradish peroxidase study.

The neurons of the mesencephalic periaqueductal grey substance (PAG) in the rat are small and medium sized. The cells are frequently located in small clusters, without interdigitating glial elements and may be connected by direct membrane appositions or by gap junctions. The inner zone of the PAG is cell poor. In many cases, the cytoplasm of the cells is filled with extensive rough endoplasmic reticulum, free ribosomes, Golgi apparatus, and large lysosome-like granules. The nuclei show large indentations. The cells have a high nucleus-cytoplasm ratio. The neuropil is very extensive and particularly rich in large numbers of small unmyelinated axons, dendrites, axonal varicosities, and synaptic connections. Myelinated fibres are relatively scarce. The orientation of the fibres was studied in transverse and horizontal sections, in combination with HRP track tracing experiments. It appeared that throughout the PAG most of the fibres were orientated longitudinally. Quantitation showed that most fibres were present in the inner zones of the PAG. Moreover, the diameter of the fibres adjacent to the aqueduct was smaller than that of the fibres in the peripheral parts of the PAG. The thin unmyelinated fibres made extensive synaptic connections within the PAG. Many synaptic varicosities were found in the neuropil of the PAG. There were four types of synaptic varicosities, characterized by different populations of clear and dense-core secretory granules and by the different morphology of the synaptic specializations. In general, the different types of varicosity were homogeneously distributed in the different parts of the PAG. Electron dense secretory granules, when present, were located at some distance from the synaptic junction. Serial sections revealed varicosities which contained only dense-core secretory granules, without synaptic specializations. The dendrites of PAG neurons generally lacked synaptic spines. Many dendrites, particularly those of neurons located in the peripheral parts of the PAG, were directed toward the aqueduct. The present study shows that the PAG is a very complex brain area. The crisscrossing of axons and dendrites with synaptic connections at considerable distances from the cell bodies render it very difficult to unravel the relationships between the possible sources and destinations of ongoing information. This structure complicates the search for relationships between the functional organization and the cytoarchitectural borders in the PAG area.     

突触功能必需基因参与线虫衰老的调控(英文)

目的鉴定参与线虫衰老的神经内分泌调控的新基因。方法鉴于神经系统在衰老调控中的重要作用,通过寿命分析和脂褐质自发荧光的检测,从编码突触蛋白的遗传位点中筛选参与衰老调控的基因。我们还进一步检查了这些遗传位点相应的突变体的永久性幼虫形成情况,探讨它们是否可能受胰岛素样信号通路的调控。结果遗传位点 unc-10,syd-2,hlb-1,dlk-1,mkk-4,scd-2,snb-1,ric-4,nrx-1,unc-13,sbt-1,unc-64 可能参与线虫衰老的调控。而且在衰老的调控中,unc-10,syd-2,hlb-1,dlk-1,mkk-4,scd-2,snb-1,ric-4,nrx-1 的功能可能与unc-13,sbt-1,unc-64相反。肠道脂褐质自发荧光的检测进一步证明了筛选出的各基因对应突变体的长寿或短寿表型,是由减慢或缩短的组织衰老所致。在筛选出的基因中,syd-2,hlb-1,mkk-4,scd-2,snb-1,ric-4,unc-64 也参与了永久性幼虫形成的调控。另外,daf-2突变增强了syd-2和hlb-1的表达,降低了mkk-4,nrx-1,ric-4,sbt-1,rpm-1,unc-10,dlk-1,unc-13 的表达。daf-16突变提高了syd-2和 hlb-1 的表达,降低了mkk-4,nrx-1,sbt-1,rpm-1,unc-10,dlk-1,unc-13 的表达. 结论突触功能可能在个体寿命和永久性幼虫形成的调控机制中具有重要的作用。     

Parvalbumin immunoreactivity reveals layer IV of monkey cerebral cortex as a mosaic of microzones of thalamic afferent terminations

Correlative light and electron microscopic immunocytochemical methods were used to study the pattern of staining for the calcium-binding protein parvalbumin (PV) in the primary visual area (area 17) and area 3b of the first somatic sensory area of the monkey cerebral cortex. A conspicuous feature of the light microscopic staining pattern is the presence of focal aggregations of immunoreactive terminal-like puncta within the major thalamic recipient layers (IV and VI). At the electron microscopic level these aggregations of puncta are found to be immunoreactive terminals most of which form asymmetric synapses, principally on dendritic spines and, to a lesser extent, on dendritic shafts. Outside the aggregations, most PV-immunoreactive terminals form symmetric synapses. Correlative observations in the present and other studies indicate that the aggregations of PV-immunoreactive terminals forming asymmetric synapses arise from thalamic afferent fibers while those forming symmetric synapses arise from intrinsic gamma-aminobutyric acid neurons. The aggregations of PV immunoreactivity in layers IV and VI form microzones of preferred thalamic afferent terminations which may contribute to the formation of functional columns based upon focussed thalamic inputs.     

电针对大鼠海马兴奋性突触后电位长时程增强的作用

目的 观察电针对麻醉状态下正常和东莨菪碱引起的学习记忆减退模型大鼠海马突触EPSP长时程增强(LTP)的作用。方法 引导大鼠海马齿状回颗粒细胞层突触后兴奋性电位群(EPSPs)，强直刺激(HFS)大脑皮层前穿质区引起海马突触LTP反应；用东莨菪碱制备学习记忆障碍模型；观察电针大椎和肾俞穴对正常和模型大鼠海马LTP的影响。结果 电针对HFS诱发的海马突触LTP效应，其作用强于未电针组，部分参数和时段有统计学意义(P＜0．05)，且维持时间长于后者；东莨菪碱i．p可显著抑制HFS诱发的海马突触LTP(P＜0．01)，电针能显著对抗这一抑制作用(P＜0．01；P＜0．05)。结论 电针对HFS引起的海马突触LTP有一定的易化作用，并对东莨菪碱引起的学习记忆障碍有显著的对抗作用。     

Characterization of HPC-1 antigen, an isoform of syntaxin-1, with the isoform-specific monoclonal antibody, 14D8

We raised polyclonal and monoclonal antibodies against rat recombinant HPC-1/syntaxin 1A lacking a transmembrane domain. The polyclonal antibody recognized two major bands at 35 and 40 kDa from rat brain membranes. A hybridoma clone designated 14D8, however, recognized only one band at 35 kDa. A polyclonal antibody detected recombinant syntaxin 1B, as well as HPC-1/syntaxin 1A on an immunoblot, whereas 14D8 recognized recombinant HPC-1/syntaxin 1A, but not syntaxin 1B. Therefore, 14D8 is specific for HPC-1/syntaxin 1A. Using this monoclonal antibody, we investigated the expression of HPC-1/syntaxin 1A in the rat hippocampal membranes. HPC-1/syntaxin 1A was present even in the embryonic d 19 (E19) hippocampal membranes, and it increased during the next two postnatal wk. Pyramidal cell axons were intensely stained with the 14D8 monoclonal antibody, suggesting that HPC-1/syntaxin 1A was not restricted to the presynaptic terminal. Furthermore, we investigated the phosphorylation of HPC-1/syntaxin 1A in the rat brain membranes. HPC-1/syntaxin 1A affinity-purified on a 14D8 IgG-coupled column was recognized by antiphophoserine antibody, but not by antiphosphotyrosine and phosphothreonine antibodies.     

Distribution of input synapses from processes exhibiting GABA- or glutamate-like immunoreactivity onto terminals of prosternal filiform afferents in the locust

The locust prosternum carries a population of long filiform hairs that are very sensitive to air currents. The sensory afferent neurons that innervate the hairs make strong monosynaptic connections with an identified intersegmental interneuron (A4I1) which is known to contact motor neurons that supply muscles controlling wing angle during flight. In order discover how the synapse between the afferents and interneuron A4I1 might be modulated, the afferents were labelled intracellularly by backfilling with horseradish peroxidase to reveal their central terminals which lie in the prothoracic ganglion. A postembedding immunogold method was used to make a quantitative assessment of the prevalence of immunoreactivity for GABA and glutamate in processes presynaptic to the afferent terminals. In one afferent neuron, where 77 synapses were examined, 40 (52%) of the presynaptic processes were immunoreactive for GABA. When adjacent sections through the same terminal branches were labelled with the two antibodies, it was demonstrated that GABA- and glutamate-like immunoreactivity was present in different populations of presynaptic processes. A series of 110 ultrathin sections was cut through one set of afferent terminal branches and alternate grids were stained with GABA and glutamate antibodies. From these sections, the terminals were reconstructed and the position of 35 input and 21 output synapses mapped. Of the 35 input synapses, 18 (51%) were immunoreactive for GABA, 14 (40%) were immunoreactive for glutamate and 3 (9%) were unlabelled by either antibody. On these terminals, the different classes of input synapses appeared to be intermingled at random with the output synapses made by the afferent, and no pattern govering synapse distribution could be discerned. © 1994 Wiley-Liss, Inc.