摘要:

AbstractGolgi studies in newborn kittens show that the two most prevalent interneurons in Rexed's lamina II of the dorsal horn of the medulla, the stalked cell and islet cell (Gobel, 1975a,b, 1978b) form their dendritic arbors in a similar fashion. At birth, both cell types are present in forms ranging from immature, in which numerous short dendrites radiate from the cell body in all directions, to relatively mature in which their dendritic arbors have elongated in specific directions and the adult branching pattern is already evident. During postnatal maturation, many dendrites are lost while only a few go on to lengthen. The unmyelinated axons of both cells are first recognized in forms in which lengthening dendrites have taken on their preferred direction of orientation.The two parts of Rexed's lamina II, i.e., layers IIa and IIb have already reached their adult mediolateral width at birth and the neuropil has nearly achieved its adult compactness. Space in the compact neuropil for elongating neuronal and astrocytic processes becomes available through the disintegration of many existing dendrites and by an overall fourfold increase in the rostrocaudal length of the dorsal horn of the medulla during postnatal maturation. At birth, the lengthening of the plasma membranes of elongating neuronal and astrocytic processes proceeds as vesicles (addition vesicles) found in aggregates throughout dendrites, unmyelinated axons and astrocytic processes fuse with and become incorporated into the existing plasma membranes.In addition, many dendrites in layers IIa and IIb are beading up and disintegrating. Within the beads, neurotubules are lost and addition vesicles fuse with each other to form small cavities. These cavities continue to enlarge, hollowing out the beads. The cavities ultimately open to the intercellular space as their membranes fuse with the plasma membrane of the beads. Finally, the beads disintegrate and their plasma membranes fragment. The thread‐like segments between adjacent disintegrating beads shrivel until they ultimately disappear. Disintegration of beaded dendrites results in very little debris and does not provoke a phagocytic glial reaction. The disintegration of a dendritic branch takes place in spite of synaptic input from non‐primary axons and is thought to occur from a failure to establish synaptic connections with primary axonal endi

ISSN:0092-7317    

DOI:10.1002/cne.901870102

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe efferent connections of the medial (MHb) and lateral (LHb) habenular nuclei in the rat were demonstrated autoradiographically following small injections of tritiated amino acids localized within various parts of the habenular complex. Comparison of individual cases led to the following conclusions.MHb efferents form the core portion of the fasciculus retroflexus and pass to the interpeduncular nucleus (IP) in which they terminate in a topographic pattern that reflects 90° rotations such that dorsal MHb projects to lateral IP, medial MHb to ventral, and lateral MHb to dorsal IP. Most MHb fibers cross in the interpeduncular nucleus in the “figure 8” pattern described by Cajal, and terminate throughout the width of IP with only moderate preference for the ipsilateral side. However, the most dorsal part of MHb projects almost exclusively to the most lateral IP zone in a cluster pattern that is particularly dense on the ipsilateral side. The MHb appears to have no other significant projections, but very sparse MHb fibers may pass to the supracommissural septum and to the median raphe nucleus.Except for some fibers passing ventrally into the mediodorsal nucleus, all of the LHb efferents enter the fasciculus retroflexus and compose the mantle portion of the bundle. No LHb projections follow the stria medullaris. In the ventral tegmental area LHb efferents become organized into groups that disperse in several directions: (a) Rostrally directed fibers follow the medial forebrain bundle to the lateral, posterior and dorsomedial hypothalamic nuclei, ventromedial thalamic nucleus, lateral preoptic area, substantia innominata and ventrolateral septum. (b) Fibers turning laterally distribute to the substantia nigra, pars compacta (SNC); a small number continue through SNC to adjacent tegmentum. (c) The largest contingent of LHb efferents passes dorsocaudally into paramedian midbrain regions including median and dorsal raphe nuclei, and to adjacent tegmental reticular formation. Sparse additional LHb projections pass to the pretectal area, superior colliculus, nucleus reticularis tegmenti pontis, parabrachial nuclei and locus coeruleus. No LHb projections appear to involve the interpeduncular nucleus. All of these connections are in varying degree bilateral, with decussations in the supramammillary region, ventral tegmental area and median raphe nucleus.On the basis of differential afferent and efferent connections, the LHb can be divided into a medial(M‐LHb) and a lateral (L‐LHb) portion. The M‐LHb, receiving most of its afferents from limbic regions and only few from globus pallidus, projects mainly to the raphe nuclei, while L‐LHb, afferented mainly by globus pallidus and in lesser degree by the limbic forebrain, projects predominantly to a large region of reticular formation alongside the median raphe nucleus. Both M‐LHb and L‐LHb, however, project to SNC. The reported data are discussed in correlation with recent histoc

ISSN:0092-7317    

DOI:10.1002/cne.901870103

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractPatterns of dendritic development in the neocortex of normal and reeler E15‐17 mouse embryos are studied in Golgi impregnations. Interactions between dendrites and axon‐rich strata appear to be critical determinants of dendritic morphology in both genotypes. Firstly, axon‐dendrite proximity appears to stimulate dendritic sprouting, elongation and branching. Secondly, the position of the axon‐rich strata with respect to the differentiating cell appears to determine the direction of dendritic growth and thereby the ultimate configuration of the dendritic arbor. With regard to specific cell configuration, a multipolar form is generated when the cell is embedded in an axon‐rich zone. A monopolar or bipolar configuration is achieved when the cell lies in the axon‐poor cortical plate and addresses an axon‐rich stratum with one or both radially extended migratory processes. Such variations in the configuration of neurons with polar dendritic systems may be observed uniquely in the mutant cortex be cause axon‐rich zones are stratified anomalously at multiple levels in the cortical plate. As a consequence, polar dendritic systems develop from either the superior, the inferior or both somatic poles of postmigratory cells. Pyramidal cells may, therefore, develop a normal upright or an abnormal “upside‐down” disposition. Regardless of the orientation of the polar dendritic system, the axon emerges from the inferior aspect of the cell suggesting that there has been no rotation of the original migra

ISSN:0092-7317    

DOI:10.1002/cne.901870104

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe spatio‐temporal distributions of excitatory synaptic ensemble activities in A17 and A18 of the visual cortex of the macaque monkey have been investigated. The synaptic activities were elicited by electrical stimulation of the primary afferents and were localized by applying the current source density analysis to the intracortically recorded field potentials. The principal results are as follows.1.In A17, two groups of activity, evoked by fast and slow afferents, respectively, were distinguishable.2.The fast afferents induce monosynaptic activity in layer IV Cα and layer VI, disynaptic activity in layer IV Cα and in the supragranular layers and trisynaptic activity in layer IV B.3.The slow afferents induce monosynaptic activity in lower layer IV Cβ and layer VI, disynaptic activity via strong connections in upper layer IV Cβ, further disynaptic activity in layers III and IV B and trisynaptic activity in layers V A and II.4.With the exception that the CSD data reveal more polysynaptic activity within layer IV, there is good agreement between the spatio‐temporal distribution of synaptic activities and the cortical circuit diagrams proposed in anatomical studies.5.In A18, activities from the slow and fast conducting afferent systems are revealed in layer IV, both most likely mediated by the monosynaptically activated target cells of A17. These activities are passed on to the supra‐ and infragranular lavers.6.In the lateral geniculate nucleus the safety factor of transmission is higher for activity conveyed by slow‐ than by fast‐conducting retinal afferents.7.The spatial distribution of monocularly evoked surface potentials failed to reveal the ocular dominance columns.8.Comparison with the cat indicates that, with respect to the intracortical circuitry and LGN‐transmission, there are more similarities between the fast‐group activity in the monkey and the x‐system in the cat and between the slow‐group activity in the monkey and the y‐system in

ISSN:0092-7317    

DOI:10.1002/cne.901870105

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe cytoarchitecture of the ventral tegmental area of Tsai (VTA) has been studied in detail in the rat with the aid of both conventional techniques and glyoxylic acid‐fluorescence histochemistry. Three main dopamine containing cells groups can be distinguished: nucleus paranigralis, nucleus parabrachialis pigmentosus lies dorsally, and nucleus paranigralis ventrally in the VTA, while nucleus linearis continues posteriorly and medially from VTA and extends dorsally in the midline up towards the dorsal raphe nucleus. Fluorescent neurons in these three groups correspond to the A10 group. In addition to these previously described findings, the present study shows evidence for a further small but cytoarchitecturally distinct dopaminergic group called the interfascicular nucleus. This lies anterorly and ventrally in the ventral tegmentum in the midline, dorsal to the rostral portion of the interpeduncular nucleus and interpeduncular fossa.The significance of these cytoarchitectural findings in discussed in relation to the known connections of the regio

ISSN:0092-7317    

DOI:10.1002/cne.901870106

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe ventral tegmental area of Tsai (VTA) and interfascicular nucleus of the adult rat brain has been studied with two variants of the Golgi method in three planes of section. Neurons were studied in relation to the cytoarchitectural groupings of the VTA. Dendritic organisation and dendritic fields were mapped out for each cytoarchitectural subgroup and cell types within each subgroup were classified on the basis of cell size and dendritic morphology.In each subnucleus of VTA, neurons had distinct characteristics. In nucleus paranigralis neurons were small to medium in size and their dendritic fields organised in an approximately horizontal plane orientated in an anteromedial direction and slanting dorsally over the interpeduncular nucleus and fossa. Neurons of the parabrachial group were small to medium sized with no preferential orientation. In nucleus linearis raphe caudalis small neurons were strongly orientated in the plane of the nucleus in a dorso‐ventral direction slanting forwards. Neurons in the interfascicular group were small to very small and their maximum dendritic extents were seen in the horizontal plane. In frontal section they formed a compact ball of cells in the midline and were separated on either side from the larger neurons in the medial edge of nucleus paranigralis.Ingeneral VTA neurons tended to fall into one of two morphological categories. Type 1 were small to medium, and had two to four primary dendrites which divided into varicose secondary dendrites. Type 2 were medium sized, with two to five primary dendrites. Both primary and secondary dendrites and the cell soma of Type 2 neurons were moderately spiny. Secondary dendrites were not varicose. Forms also occurred which were intermediate between Types 1 and 2. In the nucleus paranigralis, Type 1 was more common medially, while Type 2 was more common laterally, particularly in the ventrolateral paranigral region. Only neurons of Type 1 were seen in nucleus linearis raphe and interfascicular nuclei. Local axon circuits were observed to arise from the primary dendrites of Type 1 neurons and to ramify close to neighbouring neurons. Axon swellings from such circuits were observed to make apparent contact with primary dendrites of nearby neurons and clusters of axon swellings were observed near cell somas of neighbouring impregnated neurons of similar type.The results are discussed and particular attention is paid to the similarities and differences between VTA and the substantia nigra pars compacts (SNC). The major difference appears to be that, whereas in SNC dendrites are organised in vertical as well as horizontal planes, in the VTA no long ventrally directed dendrites were observed. Combining these results with the known cytoarchitecture and connections of VTA and SNC, it appears that fundamental differences occur between VTA and some neurons of the SNC, both in the nature of their morphology and intrinsic organisation, and in the organisation of their efferent and afferent connection

ISSN:0092-7317    

DOI:10.1002/cne.901870107

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractUsing the retrograde transport of horseradish peroxidase (HRP), a study has been made of projections to the ventral tegmental area of Tsai (VTA) and related dopaminergic cell groups (A 10). In order to minimise the possibility of damage to fibres of passage, a technique was evolved for the microiontophoresis of HRP such that minimal current strengths and durations were applied. In addition to a sham injection, control injections were also made to the medial leminiscus, red nucleus, deep tegmental decussations, mesencephalic reticular formation and brachium conjunctivum. Following HRP injections confined to the areas of the VTA containing the dopamine cell groups, labelled neurons appeared in prefrontal cortex, dorsal bank of rhinal sulcus, nucleus accumbens, bed nucleus of stria terminalis, amygdala, diagonal band of Broca, substantia innominata, magnocellular preoptic area, medial and lateral preoptic areas, anterior, lateral and postero‐dorsal hypothalamus, lateral habenular, nucleus parafascicular nucleus of thalamus, superior colliculus, nucleus raphe dorsalis, nucleus raphe magnus and pontis, dorsal and ventral parabrachial nuclei, locus coeruleus and deep cerebellar nuclei. Regions containing catecholamine goups A 1, A 5, A 6, A 7, A 9, A 13 and the serotonin group B 7 corresponded to the topography of labeled cell groups. Injections of HRP to the interfascicular nucleus resulted in labeling predominantly confined to the medial habenular and median raphe nuclei. The results are discussed in relation to the known connections of these regions. Other regions of the brain labelled by VTA injections are assessed in relation to control injections and the limitations of the HRP technique.A review of the organisation of some of these afferents in relation to the known cortical‐subcortical‐mesencephalic projection systems, suggests that the VTA is in a position to receive information from a massively convergent system derived ultimately from the entire archi‐, paleo‐, and neo‐cerebral cortices. In addition A 10 dopaminergic neurons are known to project to restricted regions of both pre‐frontal and entorhinal cortices, which themselves also receive massively convergent association cortico‐cortical connections. It would appear reasonable to propose that these neurons perform a correspondingly important integ

ISSN:0092-7317    

DOI:10.1002/cne.901870108

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractElectrophysiological recording of single neurons was used to describe the representation of visual space in area 17, and the technique of retrograde transport of horseradish peroxidase (HRP) was applied to relate these results to projections from the thalamus in the prosimian primateMicrocebus murinus. The visuotopic organization of area 17 was found to resemble that of other primates. On the dorsal surface, the border of area 17 corresponds to the representation of the vertical meridian. Proceeding medially across the surface the location of receptive fields descends along the vertical meridian, while moving caudally receptive fields progress temporally. Most of the dorsolateral surface is devoted to central vision and corresponds to a well developed area centralis. Following HRP injections in striate cortex, columns of labeled cells were found in the dorsal lateral geniculate (dLGN) extending orthogonally across all six layers. These columns run in a general ventrodorsal and caudorostral direction, parallel to a line connecting the cellular discontinuities corresponding to the optic disc. These discontinuities are present in magnocellular layer 1 and parvocellualr layers 5 and 6, thus receiving from the nasal retina of the contralateral eye. The representation of the vertical meridian is situated in the ventromedial portion of the dLGN, and the monocular field is represented in the dorsal extremity. Anterior dLGN projects to the calcarine fissure (lower field). and posterior dLGN projects to the ventral surface of the cortex (upper field). Exptrgeniculate input to area 17 was found to originate from the pulvinar. HRP labeled cells were located in two distinct divisions of this nucleus, the cytoarchitecture of which is described. In addition, projections to occipital cortex were found to arise form the intralaminar nuclei.

ISSN:0092-7317    

DOI:10.1002/cne.901870109

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractA population of microglial cells that rapidly incorporate extracellular material introduced into the ventricular system has been identified just beneath the ependyma of all four cerebral ventricles in the toad(Bufomarinus). In untreated tissue these cells appear to be scatterd, possess few processes and have and elongate shape with their long axes lying parallel to the ventricular surface. Their most distinctive ultrastructural features are nucleicontaining clumps of chromatin, cytoplasmic dense bodies and single strands of granular endoplasmic reticulum. When horseradish peroxidase (HRP) is perfused through the ventricular system and the tissue processed using the DAB cytochemical method, the cells change shape and incorporate HRP into cytoplasmic structures. Even after very short perfusion periods (2–5 minutes) cells become rounded, the surface is ruffled and pseudopodia develop that contain characteristic flocculent material. Reaction pruduct for HRP is contained in plain and coated vesicles, tubules, vacuoles and long structures composed of two closely apposed menranes. At these early times, relatively few multivesicular bodies and dense bodies contain reaction product, but when the cells are viewed at longer time periods after the ventricular perfusion of HRP an increasing proportion of the multivesicular bodies and dense bodies contain reaction product. By 320 minutes reaction product is found almost exclusively in these two organelles. In addition, many pseudopodia containing dense bodies with peroxidase activity are found in the neuropil; some, but not all, can be traced from the subependymal microglial cells. The cell bodies have resumed their flattened shape, When compared to the subependymal microglial cells, other brain cells‐oligodendrocytes, astrocytes, ependymal cells and neurons‐contain relatively little reaction product at short time intervals; only by 320 minutes are moderate amounts of HRP present. Because of the position of the microglial cells and their ingestive capacity, it is suggested that they function to protect the brain from foreign substances entering form th

ISSN:0092-7317    

DOI:10.1002/cne.901870110

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY

摘要:

AbstractThe time courese for the appearance and removal of degenerating terminals and the loss and reappearance of intact terminals were investigated in the partially denervated inner molecular layer of the dentate gyrus of the adult rat. Dense degeneration was evident in the neuropil within 26 hours following contralateral hippocampectomy. These profiles increased rapidly in number until the maximal degree was reached at two to tree days postlesion, after which the degenerating terminals were quickly removed from the neuropil. A more rapid rate of removal occurred during the 3‐ to 5‐ day survival period than from 6 to 50 days postlesion.The intact terminal population dropped by 35% within two days of the lesion and remained at this level until six to eight days postlesion when the number began to steadily increase. The time course for this reappearance cat be divided into two phases: a period of rapid terminal addition from 6 to 15 days followed by a phase of slower acquisition. This recovery continued until the normal synaptic density was regained by 50 to 65 days postlesion.These results indicate that a substantial proportion of degenerating endings are removed well in advance of the time at which terminal proliferation begins, suggesting that certain changes other than merely the removal of competitive inputs must take place prior to the gowth of new terminals. Possible explanations suggested by the present results for the delay in the onset of sprouting in clude: (1) an absence of appropriate postsynaptic targes during the 2‐ to 5‐ day postlesion period and (2) inhibition of axonal growth by the glial cells which are phagocytizing the degenerating products.Beyond the sixth postlesion day the rate at which new terminals appear does correlate with the rate at which degeneration is removed. This suggests that once underway the time course for sprouting may be determined by the availability of postsynapti

ISSN:0092-7317    

DOI:10.1002/cne.901870111

出版商:The Wistar Institute of Anatomy and Biology    

年代:1979

数据来源: WILEY