摘要:

AbstractThe morphology and connections of the indusium griseum (IG) and anterior hippocampal continuation (AHC) suggest that this cortex contains analogues to several portions of the hippocampal formation. Whereas the outer neuronal layer of this cortex is made up of cells which are similar in structure to the neurons of the granule cell layer of the dentate gyrus, the three successively deeper layers contain morphological analogues to the neurons of the dentate hilus, Ammon's horn, and the subiculum, respectively. The neurons within each of these four layers of the AHC and IG have afferent and efferent connections which are quite similar to the connections of their hippocampal counterparts. Thus, the granule cells of the IG and AHC receive laminar inputs from the entorhinal cortex, the IG‐AHC itself, and the supramammillary region. Each of these three classes of inputs ends at successively more proximal positions on the dendritic tree of these granule cells. Other inputs to this region include those from the septal nuclei and the olfactory bulb. The deeper layers of the IG and AHC receive several inputs, including those from the thalamic and septal nuclei and the entorhinal cortex. The efferent cell bodies of the IG and AHC are segregated in such a way that the granule cells appear to give rise to only short connections, while the hilar cells project to the granule cells, the intermediate pyramidal neurons project to other portions of the IG and AHC and to the olfactory bulb, and the deep pyramidal neurons project to the diencephalon. These results demonstrate that the IG‐AHC is a continuation of the hippocampal format

ISSN:0092-7317    

DOI:10.1002/cne.902190302

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe distribution and dendritic organization of splenius motoneurons innervating extrafusal muscle fibers in different regions of the muscle were examined by electrophysiological and intracellular HRP staining techniques. Motoneurons innervating the regions of the splenius muscle supplied by the C2, C3, and C4 peripheral nerves were arranged in three nonoverlapping sub‐nuclei. Reconstructions of the dendritic trees of splenius motoneurons in these three subnuclei showed that there were no major differences in their dendritic distributions. Instead, the dendritic distribution followed a single pattern which was composed of five major dendritic projections. These included a dorsolateral projection to the lateral part of lamina VIII, a lateral projection into the spinal accessory nucleus and beyond the gray‐white border, ventral and ventrolateral dendrites in the lateral half of the ventromedial nucleus and the surrounding white matter, medial dendrites which projected both dorsally and ventrally, and finally a conspicuous collection of dendrites which projected rostrally and caudally from the cell body.These results indicate that the dendritic distributions of splenius motoneurons are not related to the segmental position of the motoneuron or the zone of the muscle innervated by the motoneuron. However, a comparison of the dendritic distribution of splenius motoneurons to the dendritic distribution of biventer cervicis‐complexus motoneurons indicated that there are major differences in the form of their dendritic trees even though dendrites from both sets of motoneurons share the same territory. As a consequence, although these motoneurons may receive the same connections, the effect of these connections on the excitability of the motoneurons may d

ISSN:0092-7317    

DOI:10.1002/cne.902190303

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractStimulation of the contralateral hippocampus in the hilar region had a marked effect on granule cell excitability in the fascia dentata. The primary effect was to block the population spike that otherwise occurred in response to perforant path stimulation. In contrast, the size of the excitatory post‐synaptic potential component of the perforant path‐evoked field potential was only slightly reduced. The population spike diminution began at short latency (3.5 msec), beginning at about 1.0 msec after the onset of the slow component of the potential evoked by the contralateral stimulus. The completeness and duration of this population spike diminution depended on the contralateral stimulus intensity. The maximum duration was less than 40 msec in unanesthetized rats and more than 100 msec in rats under pento‐barbital anaesthesia. Bicuculline did not diminish the field potential evoked bythe contralateral stimulus but it did prevent the stimulus from blocking the perforant path population spike and, instead, permitted a weak facilitation of the population spike. The normal reduction of the population spike was not mediated by recurrent inhibition, secondary to granule cell activation, since it occurred whether or not the granule cells were inhibited at the time of contralateral stimulation. These results imply that the initial main effect on fascia dentata granule cells of activity in the contralateral hilus is a γ‐aminobutyric‐acid‐mediated inhibition. This effect most probably involves commissural excitation of local inhibitory interneurons. The direct excitatory action of commissural fibers on granule cells, by comparison,

ISSN:0092-7317    

DOI:10.1002/cne.902190304

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractRoughly one‐quarter of neurons in the amacrine cell layer accumulate exogenous γ‐aminobutyric acid (GABA). Some of these (8%) are interplexiform cells; the remainder are true amacrine cells. We partially reconstructed, from serial electron microscope autoradiograms, 25 GABA‐accumulating amacrines and distinguished four types based on cytoplasmic appearance, soma size and shape, and the form of primary and secondary processes. Type 1 had a large (609 ± 60 μm3), dark soma, and multiple, medium‐diameter (0.6 μm) processes splayed from the soma margins like the appendages from a crab. Type 2 had a medium (360 ± 40 μm3), helmet‐shaped, pale soma, and medium‐diameter (0.8 μm) processes that branched in sublamina α. Type 3 had a small (267 ± 44 μm3), dark, pyriform soma. The latter formed a single stout (3.0 μm) process that bifurcated in the middle of sublamina α. Type 4 had a very large, pale soma (860 μm3). This was pyriform, tapering into a stout (2.0 μm) process that descended into the middle of sublamina α where it emitted smaller tangential processes. It is to be expected that each of these amacrine cell types will have distinct functions in neurotra

ISSN:0092-7317    

DOI:10.1002/cne.902190305

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractImmunohistochemical methods were used to (1) characterize the organization of descending striatotegmental pathways in two species of reptiles, thecrocodilianCaiman crocodilusand the turtleChrysemys scripta, and (2) compare the organization of the Striatotegmental pathways in these species to those of mammalian and avian species. In turtles, numerous substance P‐containing neurons were found in the medial portions of the small‐celled subdivision of the basal ganglia (paleostriatal complex), termed area d (Riss et al., ′69), and paleostriatum augmentatum (PA). In caiman numerous substance P‐containing neurons were also located within medial portions of the basal ganglia, including the small‐celled portion of the ventrolateral area of the telencephalon (VLA s.c.) and the dorsomedial portion of the large‐celled component of the ventrolateral area of the telencephalon (VLA I.c.). In both caiman and turtle, substance P‐containing fibers could be followed from the medial small‐celled fields into the medial forebrain bundle. The substance P (SP) fibers of the medial forebrain bundle are continuous caudally with several substance P‐rich fiber plexuses in the midbrain tegmentum. The substance P‐rich tegmental fields include the area ventralis of Tsai (AVT) and the substantia nigra (SN) in turtle. In caiman, these regions are called the area ventralis of Tsai and the nucleus tegmenti pedunculopontinus (TP)1. Knife cuts placed in the course of the SP‐containing fibers of the medial fore‐brain bundle resulted in a loss (in the case of complete transections) or diminution (in the case of incomplete transections) of the substance P‐containing fibers in AVT and SN or TP.Both the SN of turtle and the TP of caiman can be subdivided into two portions. Each contains a zone of densely packed catecholaminergic neurons and a more ventrally situated cell‐poor zone containing no catecholamine neurons. The distribution of catecholamine neurons was determined by the use oftyrosine hydroxylase (TOH) immunohistochemistry. The celldense zones of SNand TP (called the pars compacta of SN, or SNc, and the pars compacta of TP, or TPc) contain rich substance P fiber plexuses; however, the cell‐poor portions (called the pars ventralis of SN or SNV and the pars ventralis of TP or TPv) contain the highest levels of substance P immunore‐activity and densest substance P fiber plexuses found in the brains of these reptilian species. Immunohistochemical methods indicate that the AVT of caiman and turtle also contains many neurons positive for tyrosine hydroxy‐lase immunoreactivity (i.e., catecholaminergic neurons) and a rich substance P fiber plexus.Immunohistochemical methods were also used to map the distribution of serotonin (5‐HT) within the caiman and turtle brains. The results show that the terminal fields of the substance P‐containing striatotegmental fibers in these species also contain rich plexuses of serotonergic fibers, as is the case in avian and mammalian species.The results of these studies in caiman and turtles show many parallels in the organization of the descending striatotegmental path of reptiles with that of mammals and birds. As in mammals and birds, striatotegmental substance P neurons are found in the medial small‐celled portions of the basal ganglia and project upon portions of the midbrain tegmentum containing catecholaminergic neurons. These catecholamine cell groups (the AVT, SN, and TP) have themselves been shown to project back to the striatum, supplying the rich catecholamine fiber plexuses present in the basal ganglia of birds, reptiles, and mammals. These similarities inbasal ganglia organization in species of three different classes of amniotevertebrates suggest that modern amniotes inherited their striatotegmental substance P systems from a common ancestor and that many features of basal ganglia organization such as the striatotegmental and tegmentostriate systems are

ISSN:0092-7317    

DOI:10.1002/cne.902190306

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe projections of the rat area postrema were analysed using antero‐grade and retrograde axonal transport techniques. Discrete injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into the area postrema produced anterograde labeling in specific medullary and pontine nuclei. In the medulla, anterograde labeling was present in the internal solitary zone and dorsal division of the medial solitary nucleus, both of which also contained a small number of retrogradely labeled perikarya. Prominent projections to the dorsal motor nucleus of the vagus were seen only if the WGA‐HRP injections in the area postrema invaded dorsal solitary nuclei. In the pons, anterograde labeling was present in the parabrachial nuclei, the dorsolateral Legmen tal nucleus, and the pericentral division of the dorsal tegmental nucleus. By far the major pontine projection was to the dorsolateral region of the middle one‐third of the rostrocaudal extent of the parabrachial nuclei. Retrograde fluorescent tracing studies indicated that most area postrema neurons take part in this parabrachial projection. The area postrema projection to the parabrachial nuclei was bilaterally distributed, whereas that from the dorsal solitary nuclei was primarily ipsi‐lateral. The external solitary zone, immediately subadjacent to the area postrema, neither received area postrema projections nor participated in the projections to the parabrachial nuclei. Fluorescent retrograde double labeling studies confirmed the bilateral nature of the area postrema projection to the parabrachial nuclei. In addition, because no doubly labeled neurons were observed it appears that individual area postrema neurons project to either side but not both sides of the dorsal pons. Thus, numerous neuronal pathways exist for the transfer of blood‐borne information (that cannot cross the blood‐brain barrier) from the area postrema to other

ISSN:0092-7317    

DOI:10.1002/cne.902190307

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractTo determine the dendritic fields, mitral, displaced mitral, middle tufted, and granule cells in the rabbit olfactory bulb were stained by intracellular injection of HRP. The secondary dendrites of mitral cells were distributed mostly in the inner half of the external plexiform layer (EPL). Those of displaced mitral cells extended mainly into the middle and superficial sublayers in the EPL. The secondary dendrites of middle tufted cells weredistributed mostly in the superficial portion of the EPL.Mitral cells extended their secondary dendrites in virtually all directions within a plane tangential to the mitral cell layer (MCL) and thus had a disklike projection field with a radius of about 850 μm. Displaced mitral cells had similar dendritic projection fields in the tangential plane but with somewhat distorted shapes. The secondary dendrites of middle tuftedcells had a tendency to extend in particular directions.From the projection pattern of the gemmules on the peripheral processes, granule cells were classified into three types. Type I granule cells had gemmules both in the superficial and in the deep sublayers of the EPL. The peripheral processes of Type II granule cells were confined to the deep half of the EPL. The gemmules of Type III granule cells were distributed in the superficial half of the EPL.The differing dendritic ramification among mitral, displaced mitral, and middle tufted cells suggests the separation of the dendrodendritic synaptic interactions with granule cells in different sublayers in the EPL. It also suggests a functional separation of the sublayers of the EPL

ISSN:0092-7317    

DOI:10.1002/cne.902190308

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

摘要:

AbstractThe number of ganglion cells in the retina of the postnatal rat has been examined. We estimated both the number of axons in the optic nerve and the number of cells which can be retrogradely labelled with horseradish peroxidase from injections into the brain. In the retina of the newborn rat there are at least twice as many ganglion cells as in the adult rat. By retrograde labelling of the ganglion cells and following transection of their axons 24‐48 hrs later we can find no evidence that ganglion cells withdraw their axon without degeneration of the parent cell body. We have found that the excess ganglion cells are lost over the first ten postnatal days and during this period we observe pyknotic nuclei in the ganglion cell layer. From our estimates of the total number of neurones in the ganglion cell layer and the number of ganglion cells found at different ages we conclude that themigration of amacrine cells into the ganglion cell layer occurs in the first five postnatal day

ISSN:0092-7317    

DOI:10.1002/cne.902190309

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902190301

出版商:Alan R. Liss, Inc.    

年代:1983

数据来源: WILEY