摘要:

AbstractWe used light and electron microscopic immunocytochemical methods to examine the structure of neuronal perikarya and processes containing cholecystokinin‐like immunoreactivity (CCK‐IR) in area CA1 of the rat hippocampus. The morphology of stained perikarya, their positions within all laminae, and the orientation of their dendrites indicate that CCK‐IR is located in interneurons. These cells were seen in the electron microscope to have deeply folded nuclei and to receive both symmetric and asymmetric synaptic junctions on their cell somata and dendritic shafts. Their dendrites are essentially spine‐free, but form bulges at the site of some asymmetric synaptic junctions. Axonal varicosities containing CCK‐IR make symmetric synaptic junctions with cell somata and dendritic shafts of both pyramidal and non‐pyramidal neurons. In addition, CCK‐IR varicosities form symmetric junctions with unstained non‐pyramidal neurons and with CCK‐IR cells, suggesting either recurrent innervation of one cell on itself or interaction between interneurons. The presence of CCK‐IR varicosities and synaptic junctions on pyramidal cells is in agreement with physiological data which indicate that CCK has a direct postsynaptic action. The observation of CCK‐IR varicosities forming synaptic junctions on non‐pyramidal cells suggests that CCK might also modify the r

ISSN:0092-7317    

DOI:10.1002/cne.902330202

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was injected intracellularly into single, physiologically‐identified X‐ and Y‐cell geniculocortical axons projecting to area 17 of the cat. This injection anterogradely labeled the axon terminal fields in cortex and retrogradely labeled the somata of these same axons in laminae A and A1 of the lateral geniculate nucleus (LGN). The laminar projections of 21 X‐ and 15 Y‐cell axons were analyzed. For these, the laminar terminations of ten X‐ and seven Y‐cell axons were also related to their cells' positions in the A‐laminae.The terminal fields of X‐ and Y‐cell axons overlapped substantially in layers IV and VI of area 17. Some X‐cells terminated mainly in IVb, others mainly in IVa, and still others throughout IVa and IVb. The latter two groups also projected up to 100 μm into lower layer III. Y‐cells terminated primarily in layer IVa and projected up to 200 μm into lower layer III. Some also arborized throughout the depth of layer IVb. Both X‐ and Y‐cell axons terminated throughout the depth of layer VI, although more so in the upper half. We found no relationship between the diameter of the parent axon and its sublaminar projection within layer IV.Within layer IV, X‐cell axons generally terminated within a single, continuous clump and had surface areas of 0.6 to 0.9 mm2. Axons of Y‐cells often terminated in two to three separate clumps, separated by terminal free gaps 400 to 600 μm wide. Their total surface areas, including gaps, were 1.0 to 1.8 mm2, roughly 1.6 times the surface areas of X‐cell axons. Despite considerable overlap, Y‐cell arbors contained significantly more boutons than did X‐cell arbors.The sublaminar projections of the X‐ and Y‐cell axons within layer IV reflected the locations of the cells' somata within the depth of the A‐laminae. X‐cells located in the dorsal or ventral thirds of the depths of the laminae projected mainly to layer IVa or throughout layer IV in cortex. Those located in the central thirds projected mainly to layer IVb. Y‐cells showed a similar positional relationship, but they appeared to follow different rules. Y‐cells in the outer thirds of the A‐laminae projected mainly to layer IVa; those in the central thirds, in addition, expanded their projections to include layer IVb.In general, larger sized somata in the LGN gave rise to more widely spreading terminal arbors and greater numbers of boutons in cortex than did smaller somata. However, we found no significant relationship between soma size and terminal arbor extent or total boutons within each cell class (X or Y), and thus the correlation noted may result from Y‐cells having larger somata and terminal arbor extents than do X‐cells.Our results demonstrate considerable heterogeneity in the laminar projections of X‐ and Y‐cell axons within area 17. This heterogeneity reflects an underlying sublaminar organization of the parent somata within the depths of the LGN A‐laminae. The functional significance of this organization, both in the LGN and cortex, is unknown. It is clear, however, that the result of the geniculocortical projection upon layer IV is not to segregate X‐ and Y‐ afferents into lower and upper tiers. Rather, it may be to re‐establish a

ISSN:0092-7317    

DOI:10.1002/cne.902330203

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase was injected intracellularly into single, physiologically identified X‐ and Y‐cell geniculocortical axons that projected to area 18, to the 17/18 border region, or to both areas 17 and 18 via branching axons. The axon terminal fields in cortex were labeled anterogradely, and the cell bodies of the axons in the A‐laminae, lamina C. and the medial interlaminar nucleus (MIN) of the dorsal lateral geniculate nucleus (LGN) were labeled retrogradely.The laminar projections in area 18 of eight Y‐cells and one geniculate, non‐Y‐cell were analyzed. Most of the cells arborized densely within layer IVa and the lower 200 to 400 m̈m of layer III. Most provided little or no input to layer IVb or layer VI. Thus, the laminar projections of Y‐cells to layer IV of area 18 were similar to those of their area 17 counterparts, although the input to layer III was greater and rose much higher in area 18 than in area 17. The terminal arbors in area 18 were two to three times larger in lateral extent than those in area 17. They spread over 2.0 to 2.8 mm2of layer IV and occupied proportionately much greater regions of area 18 than the Y‐cell arbors in area 17. This may partially account for the large receptive fields of cortical cells in area 18, and it indicates that a small region of area 18 may receive converging inputs from a relatively wide retinotopic region of the LGN. The terminal arbors were also highly asymmetric, generally being two to four times longer anteroposteriorly than mediolaterally. These asymmetric arbors may form the structural basis for the anisotropic organization of the retinotopic map in area 18.We recovered three cells (two Y, one X) whose axons arborized in the border zone between areas 17 and 18. One Y‐cell axon had a receptive field located in the ipsilateral visual hemifield and it arborized in a small region restricted almost exclusively to the border zone. The other two cells had receptive fields on or adjacent to the vertical meridian, and they terminated on either side of the 17/18 border region as well as within it. Thus, geniculate afferents representing the ipsilateral hemifield or the vertical meridian appear to have different patterns of termination on and adjacent to the 17/ 18 border zone. Also, some X‐cell input may invade area 18 in the region immediately adjacent to the border zone.Some Y‐cell axons bifurcated in the white matter to innervate areas 17 and 18, but the majority innervated one area or the other. The bifurcations occurred at the level of the lateral sulcus or higher in cortex, within 1 to 5 mm of the termination zones in the gray matter. Of 12 well‐labeled Y‐cell axons arising from the A‐laminae of the LGN, two branched to areas 17 and 18, nine projected to area 17 only, and one projected to area 18 only. Of four lamina C Y‐cells, two branched and two projected only to area 18. Two Y‐ cells from the MIN projected to only area 18. Thus, within the A‐ and C‐ laminae there are substantial and dedicated populations of Y‐cells that project to one cortical area or the other, as well as some that project to both areas via branching axons.Finally, our data indicate little or no input of X‐cells to area 18, except across the 17/18 border zone. Of 23 axons projecting to area 18, 22 were Y‐ cells and one was unclassified. Of 35 X‐cell axons that were traced to their terminations, all p

ISSN:0092-7317    

DOI:10.1002/cne.902330204

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractBased on a gold‐toning, Golgi‐electron microscope examination of 12 small and medium‐sized spiny stellate neurons in laminae 4A, 4B, and 4C of the monkey visual cortex (area 17), the ultrastructure of the cell somata, dendrites, and axons of these neurons is described. Particular attention is paid to the synapses involving the surface of different parts of these neurons. Only symmetric synapses occur on the somata of spiny stellate neurons, and these occur with a frequency of 11.0–15.9 synapses/100 μm2perikaryal surface. Symmetric synapses also occur on dendritic shafts and, occasionally, on dendritic spines. Asymmetric synapses are occasionally present along the dendritic shafts of spiny stellate neurons, but the majority of asymmetric synapses (75–95%) occur on their dendritic spines. The initial axon segments of the smallest spiny stellate neurons possess no axo‐axonal synapses, but several symmetric synapses are present along the initial segment of a medium‐sized, spiny stellate neuron in layer 4B. Fifty‐three synapses made by boutons of the axons of these spiny stellate neurons have been identified, and all are asymmetric. Sixty per cent of the synapses are formed by boutons en passant and the remainder by the terminal swellings of spine‐like axonal appendages, boutons terminaux. Of the synapses formed by the axons of spiny stellate cells, axo‐spinous synapses outnumber axo‐dendritic synapses two to one, and axo‐dendritic synapses involve both spinous and aspinous dendrites. Evidence is presented which suggests that many of the axon terminals forming asymmetric synapses with the dendritic shafts and spines of spiny stellate neurons are derived from othe

ISSN:0092-7317    

DOI:10.1002/cne.902330205

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractA detailed description is given of the distribution of vasopressin‐immunoreactive structures in the brain of intact adult male rats. By application of a modified immunocytochemical procedure, vasopressin‐ immunoreactive fibers were detected in many new areas.In adult male rats which were castrated 15 weeks before death, vasopressin‐immunoreactive cell bodies had disappeared from the bed nucleus of the stria terminalis and the medial amygdaloid nucleus. No obvious changes were found in vasopressin‐immunoreactive cell bodies in other areas. Furthermore, a very strong reduction was seen in the density of vasopressin‐immunoreactive fibers in the olfactory tubercle, nucleus of the diagonal band and its immediate surroundings, ventral pallidum, basal nucleus of Meynert, lateral septum, septofimbrial nucleus, ventral hippocampal formation, amygdaloid area, pre‐ and supramammillary nucleus, supramam‐millary decussation, (inter)dorsomedial, parafascicular, and ventral aspect of paraventricular thalamic nuclei, zona incerta, lateral habenular nucleus, ventral tegmental area, substantia nigra, periventricular gray, dorsal and median raphe nucleus, and locus coeruleus. No changes were observed in other areas containing vasopressin‐immunoreactive fibers. These changes following gonadectomy were not observed in castrated rats which had been treated with testosterone.The results suggest that vasopressin projections from the bed nucleus of the stria terminalis and possibly from the medial amygdaloid nucleus require the presence of gonadal hormones for their normal appearance. This is in contrast to pathways arising from the hypothalamic vasopressin‐producing nuclei, which fail to show obvious changes fol

ISSN:0092-7317    

DOI:10.1002/cne.902330206

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe excitatory amino acids, aspartate and glutamate, have been proposed as retinal neurotransmitters. Aspartate aminotransferase (AAT) is an enzyme which is involved in the routine metabolism of these amino acids and may be involved in the specific synthesis of glutamate and/or aspartate for use as a neurotransmitter. On the basis of the hypothesis that increased levels of aspartate aminotransferase may reflect a transmitter role for aspartate and/or glutamate, we have localized aspartate aminotransferase in the guinea pig and cynamolgus monkey retinas with light and electron microscopic immunohistochemical techniques. AAT‐like immunoreactivity is localized to the cones of guinea pig retina and to monkey rods. Both species contain a subpopulation of immunoreactive amacrine cells as well as a subpopulation of immunoreactive cells in the ganglion cell layer. Immunostaining is seen in bipolar cells and terminals in the monkey but not in the guinea pig retina.We have performed quantitative analysis of the immunoreactive staining in the outer plexiform layer and described the synaptic organization of immunoreactive processes in the inner plexiform layer (TPL). Labeled amacrine processes in both species form synaptic contacts predominantly to and from bipolar terminals in the inner third of the IPL and to and from other amacrine and small unidentified processes in the outer portion of the IPL. The majority of labeled bipolar terminals in the monkey retina are seen in the inner third of the IPL where they synapse exclusively onto amacrine processes. Labeled bipolar terminals in the outer third of the IPL occasionally synapse onto ganglion processe

ISSN:0092-7317    

DOI:10.1002/cne.902330207

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSynaptic interactions between sensory and motor neurones in the locust flight system have been investigated by using intracellular labelling with cobalt and nickel for electron microscopy. Simultaneous axonal filling of two neurones with different concentrations of metal ions produces differential labelling, so that contacts between them in the central nervous system can be recognized. We have investigated the connectivity of the hindwing stretch receptor neurone (SR) with a direct hindwing depressor motor neurone (MN 127) known from physiological experiments to receive monosynaptic input from the SR, and an indirect hindwing depressor motor neurone (MN 112/1), for which no monosynaptic connection with the SR has been reported.We have found no direct synapses between the SR and MN 112/1, although some of their branches lie close together in the neuropile. We have, however, found some evidence for polysynaptic connections between them.There are many synapses of conventional dyadic morphology from both the lateral and mediolateral branches of the SR to MN 127; the medial branch was not examined. Those from the lateral branch contact the motor neurone on branches close to the neuropilar segment, while those from the mediolateral branch contact long, thin distal twigs. We estimate that there are about 600 anatomical synapses between these two neurones. Our results suggest that a large number of widely distributed anatomical synapses constitute the physiological synaptic connection between the SR and MN 127. The dyadic arrangement of these synapses provides an anatomical correlate for the physiologically established divergence of SR outputs onto interneurones and motor neurones.

ISSN:0092-7317    

DOI:10.1002/cne.902330208

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902330201

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY