摘要:

AbstractWe examined the pattern of cytochrome oxidase (CO), Nissl staining, and gamma‐amino butyric acid (GABA) immunoreactivity in the ventroposterior lateral nucleus (VPL) of the thalamus in monkeys that received no, total, or subtotal, ablation of the hand representations in postcentral somatosensory cortex. In unoperated animals, the region of VPL representing the hand was characterized by relatively dense and homogeneous CO staining throughout the rostral‐caudal extent of VPL. Counts of neurons in the VPL hand representation from adjacent thalamic sections processed for Nissl and GABA immunostaining indicated that there were approximately 261.4 neurons/mm2of which 78.4/mm2stained positive for GABA. GABA (+) puncta‐like terminals were readily apparent throughout the VPL.By contrast, animals that received total removals of the postcentral hand representations showed a dramatic reduction in CO staining in the VPL, which was confined to the expected location of the thalamic hand representation. Counts of neurons in the affected region from adjacent sections that underwent Nissl staining and GABA immunostaining also revealed a dramatic reduction of Nissl‐stained neurons, with a smaller reduction in the number of neurons staining positive for GABA. Specifically, large to medium‐sized (<180 μm2) GABA(‐) neurons were virtually eliminated in the affected portion of the VPL, and the numbers of GABA (+) neurons were significantly reduced. The remaining population of GABA(+) neurons was typically shrunken, and no GABA(+) puncta‐like terminals were observed in the affected region.The results obtained after subtotal ablation of the postcentral hand representations (only one postcentral area spared, 3b or 3a) differed from those obtained when total removals were made. Instead of virtually complete degeneration of medium‐sized to large neurons throughout the hand representation in VPL, as was the case with total removals, after partial removals, we found alternating regions in the VPL hand representation that appeared qualitatively normal, or dramatically degenerated. Thalamic sections stained with CO revealed light, moderate, and darkly stained patches of label within the hand representation in VP, depending on the type of cortical ablation. The most dramatic reduction of Nissl‐stained neurons coincided precisely with the lightest staining CO patches. Interestingly, the only statistically significant reduction in the number of GABA (+) neurons occurred in the light CO patches. In the thalamic regions coincident with the dark and moderately stained CO patches, the number of medium‐sized and large neurons decreased, but the number of GABA(+) neurons was comparable to normal. Optical density measurements of the dark patches also indicated a statistically significant difference from normal CO staining in this region.These findings indicate that following cortical damage, complex changes occur in thalamic circuitry. Interestingly, these changes are not confined to regions of the thalamus that have their major projection to the damaged region of cortex, but include thalamic regions in which the major projection is to undamaged regions of cortex. Thus, relatively restricted cortical damage has the potential to affect regions of cortex not directly damaged, through post‐injury changes in thalamic circuitry. Such changes in neuronal circuitry, especially at the thalamo cortical level, may serve as the neural substrate for the limited recovery of behavioral function often seen after strokes or head injury.

ISSN:0092-7317    

DOI:10.1002/cne.903600302

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractFilm autoradiography was used to investigate the expression of several neurotransmitter receptor subtypes in the transient ventricular and subventricular proliferative zones of the developing occipital lobe in two groups of macaque monkey fetuses. The first group of fetuses were between 60 and 93 days after conception (E60‐E93), when the ventricular and subventricular zones of the monkey occipital lobe produce neurons destined for the visual cortex. In the second group, fetuses were between E107 and E128, after generation of cortical neurons has ceased. In the E60–E93 group of fetuses, ventricular and subventricular zones displayed high densities of 5‐HT1‐serotonergic, D1‐dopaminergic, α1‐and α2‐adrenergic and high affinity kainate receptors. The activation of these receptors has previously been shown to stimulate cell proliferation in other cell systems. The possible involvement of these receptors in regulation of neuronal production is also supported by their absence in the deep laminae of the embryonic cerebral wall after E107, after cortical neurogenesis has been completed. The only exception is a high density of α2‐adrenergic receptors maintained near the ventricular surface long after all cortical neurons have been generated. We also found that during neurogenesis, proliferative zones in E66–E90 fetuses displayed virtually no 5‐HT2‐serotonergic, D2‐dopaminergic, β‐adrenergic, M1‐muscarinic cholinergic, gamma aminobutyric acid (GABA)A, N‐methyl‐D‐aspartate (NMDA), or β‐amino‐3‐hydroxy‐5‐menthy‐4‐isoxazole proprionate (AMPA) sites; most of these receptor subtypes have been reported to mediate the suppression of cell proliferation. The present findings suggest that dividing and/or newly generated cortical neurons are capable of receiving specific signals from multiple neurotransmitters

ISSN:0092-7317    

DOI:10.1002/cne.903600303

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractWe have stained an unusual population of retinal bipolar cells. When the low molecular weight tracer biocytin was injected into the vitreous body of rabbits, it subsequently accumulated in the somata and processes of a population of wide‐field bipolar cells. The cells have 2–4 primary dendrites. Their dendritic arbors span a field 50 to 200 μm in diameter. The axonal arbors are sparse and often highly asymmetric. The longest dimension of the axonal arbor ranges from 100 to 300 μm. The cells are moderately evenly spaced. They make up less than 1% of the total population of bipolar cells in the rabbit retina.With the whole population stained, regularities in the spatial arrangement of nearby cells can be recognized. Their dendrites often run to a common point, where they have the appearance of making contact with each other. A similar arrangement is seen for the cells' axonal arbors, so that the whole population is spatially linked in both the outer retina and the inner. The exact nature of the points of conjunction cannot be learned from light microscopy. One possibility is that the processes run together because they contact a common target. If so, the target structures (one in the outer retina and one in the inner) must be sparse. An alternative is that the points of conjunction represent synapses or gap junctions among wide‐field bipolars of this type. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903600304

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe structure and connectivity of the forebrain nucleus HVc, a site of sensorimotor integration in the song control system of oscine birds, were investigated in adult zebra finches. HVc in males comprises three cytoarchitectonic subdivisions: the commonly recognized central region with large and medium‐sized darkly staining cells, a ventral caudomedial region with densely packed small and medium‐sized cells, and a dorsolateral region with oblong cells and rows of cells. All three subdivisions project to area X and the robust nucleus of the archistriatum, with more complexity in the classes and distribution of cells than previously reported. In females, HVc is very small and has a cytoarchitecture distinct from that of the three male subdivisions. The structure of HVc in females treated with estradiol at 15 days of age is similar to male HVc.Tracer studies in males with fluorescent and biotinylated dextrans demonstrate non‐topographic projections onto HVc that may carry auditory information, including type 1 and type 2 neurons in subdivisions L1 and L3 of the field L complex, a class of neurons in nucleus interface, nucleus uvaeformis, the caudal neostriatum ventral to HVc, and intrinsic HVc connections. These data are interpreted in terms of HVc's functional properties. Additionally, the neostriatum immediately ventral to HVc receives projections from field L, ventral hyperstriatum, and caudal neostriatum, and projects to a region surrounding RA and near to or into area X. The similarity of the connectivity of HVc and adjacent neostriatum suggests the possibility that they share a common origin. © 1995 Wiley‐L

ISSN:0092-7317    

DOI:10.1002/cne.903600305

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAmacrine cells are located almost exclusively in the inner nuclear layer (INL) of the retina, but they express a variety of neurotransmitters. To begin to elucidate the relative roles of the local environment and cell lineage in determining the different neurotransmitter subtypes of amacrine cells, we combined lineage tracing and immunocytochemical techniques to map the spatial distribution and clonal origin of dopamine (DA) and neuropeptide Y (NPY) amacrine cells inXenopustadpole retina. At the earliest period of neurotransmitter expression, both DA and NPY amacrine cells were distributed preferentially in center and intermediate annular regions, and in anterior and dorsal quadrants. Most of the DA and NPY cells first emerged as scattered cells and later as clusters (of 2 or more cells) that increased in number and size up to premetamorphic stages. These results suggest that DA and NPY amacrine subtypes may be influenced by environmental cues localized to specific regions of the retina. Lineage analysis showed that the percentage of DA or NPY amacrine cells produced by most blastomere progenitors is significantly different from that predicted by the number of cells in the retina produced by those blastomeres. Only two blastomeres produced over 90% of the DA amacrine cells and only four produced 97% of the NPY amacrine cells. Some retinal progenitors did not contribute at all to these two amacrine subtypes. There also is a marked asymmetry in the blastomere origin of DA and NPY amacrine cells. Two retinal progenitors produced significant numbers of NPY but very few DA amacrine cells. This analysis provides evidence that blastomere origin restricts the developmental choices of retinal progenitors. © 1995 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903600306

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF) supports the survival and biosynthetic activities of basal forebrain cholinergic neurons and is expressed by neurons within lateral aspects of this system including the horizontal limb of the diagonal bands and magnocellular preoptic areas. In the present study, colormetric and isotopic in situ hybridization techniques were combined to identify the neurotransmitter phenotype of the NGF‐producing cells in these two areas. Adult rat forebrain tissue was processed for the colocalization of mRNA for NGF with mRNA for either choline acetyltransferase, a cholinergic cell marker, or glutamic acid decarboxylase, a GABAergic cell marker. In both regions, many neurons were single‐labeled for choline acetyltransferase mRNA, but cells containing both choline acetyltransferase and NGF mRNA were not detected. In these fields, virtually all NGF mRNA‐positive neurons contained glutamic acid decarboxylase mRNA. The double‐labeled cells comprised a subpopulation of GABAergic neurons; numerous cells labeled with glutamic acid decarboxylase cRNA alone were codistributed with the double‐labeled neurons. These data demonstrate that in basal forebrain GABAergic neurons are the principal source of locally produced NGF. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903600307

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractTo investigate the role of retinoic acid (RA) in the development of interneurons in the spinal cord, we examined the expression of cellular retinoic acid binding protein type I (CRABP I). The earliest developing interneurons in the chick spinal cord can be divided into two major groups: circumferential (C) neurons and primitive longitudinal (PL) neurons. In brachial segments, both types of interneurons began to express CRABP I at stage (st.) 13+of the V. Hamburger and H.L. Hamilton (1951, J. Morphol. 88:49–92) stage series, which is before the onset of axonogenesis. Subsequently, with the onset of axonal outgrowth, C neurons and PL neurons expressed CRABP I in their cell bodies, axons, and growth cones. The expression of CRABP I was developmentally regulated. CRABP I immunoreactivity gradually decreased after st. 36 (embryonic day [E] 10) such that no interneurons expressed this protein by E21. The transient expression of CRABP I during a period of intensive axonal growth suggested that RA may be involved in the development of interneurons. To test this idea, we implanted an all‐transRA‐containing ion exchange bead into either rostral segments of the spinal cord at st. 12–13 or into caudal segments at st. 15–16, all stages that are well before the appearance of CRABP‐I‐positive neurons in these segments. In the RA‐treated spinal cord, increased numbers of pyknotic cells were found predominantly in dorsal regions, presumably reflecting the death of neuroepithelial cells, C neurons premigratory neural crest cells. Surviving C neurons in the RA‐treated spinal cord extended their axons ventrally toward the floor plate as in control embryos. PL neurons also projected their axons rostrally or caudally in the RA‐treated spinal cord, similarly to control embryos. However, the proportion of caudally projecting PL neurons was significantly increased in segments rostral to the RA‐containing bead. These results suggest that RA may regulate the survival and axonal orientation (directionality) of subpopulations of spinal interneurons.

ISSN:0092-7317    

DOI:10.1002/cne.903600308

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe calcium‐binding protein calretinin is present in an intrinsic GABAergic and an extrinsic non‐GABAergic system in the rat and monkey hippocampal formation. Important species differences have been noted in hippocampal cell types immunostained for calretinin and the termination pattern of calretinin containing hypothalamic afferents in the hippocampus. In the present study, calretinin‐containing neurons were visualized using immunocytochemistry in the human hippocampal formation of individuals which showed no significant neuropathological alterations. Calretinin‐immunoreactivity was present exclusively in non‐granule cells of the dentate gyrus and in non‐pyramidal cells of Ammon's horn. Calretinin‐positive neurons were found most frequently in the hilus of the fascia dentata and in strate radiatum and lacunosum‐moleculare of CA1, whereas neurons in CA2 and CA3 were rarely immunostained. The majority of calretinin‐immunoreactive neurons were small, bipolar or fusiform neurons. The dendritic trees of the calretinin‐positive neurons were, for the most part, parallel to the dendrites of the principal cells. In the hilus, however, we observed cells with dendrites restricted to the hilar area. These dendrites were parallel to the granule cell layer. In the stratum lacunosum‐moleculare, neurons with dendrites oriented parallel to the hippocampal fissure were frequently detected. In general, dendrites were smooth or sparsely spiny, displaying small conventional spines. The axons usually emerged from the proximal dendrite and could be followed over long distances. Axons were thin, had small varicosities and displayed only few collaterals which branched relatively far away from the cell body. Distinct bands of darkly stained calretinin‐positive fibers occupied the innermost portion of the dentate molecular layer and the pyramidal cell layer of CA2. This distribution of calretinin‐immunoreactive structures in the human hippocampus is similar to that observed in other primates but differs from that described in lower mammals, i.e., the rat. Our findings suggest that primates may share a common hippocampal calrtinin‐containing system, presumably both the intrinsic GABAergic and the extrinsic hypothalamic non‐GABAergic compo

ISSN:0092-7317    

DOI:10.1002/cne.903600309

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractThe distribution patterns of neurons expressing mRNAs for four neuropeptides in the human striatum were studied during ontogeny by the use of in situ hybridization. The results of our study demonstrate that somatostain, enkephalin, dynorphin, and substance P mRNAs are present in striatal neuronal populations from week 12 of fetal life. Each neuronal population undergoes a specific differentiation. Neurons containing somatostatin mRNA are scattered throughout the caudate‐putamen up until birth. Neurons containing enkephalin, dynorphin, or substance P mRNAs evolve throughout fetal life in relation to caudate‐putamen and patch‐matrix compartmentalization. Neurons containing enkephalin mRNA (distinct from those containing substance P or dynorphin mRNAs) are present in the matrix from week 12 of fetal life. These neurons are preferentially distributed in the matrix and, at birth, display higher enkephalin mRNA content in the matrix than in the patches. Dynorphin mRNA is found in the caudate and putamen, preferentially in the patch neurons; nevertheless, a low level of dynorphin mRNA is also present in neurons of the caudate matrix. Substance P mRNA is initially restricted to caudate neurons. At birth, both substance P and dynorphin mRNAs are expressed at high levels in the patches. These results demonstrate that each neuropeptide gene is expressed during human fetal life in neurons with a specific topology and pace of development in relation to caudate‐putamen and patch‐matrix differentiation. These results also contribute evidence that neurochemical evolution of the striatal neuronal populations is not complete at birth in humans. © 1995 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903600310

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY

摘要:

AbstractAlcohol taken regularly over a lengthy period of time has been claimed to cause to loss of neurons in both the adult and developing brain. However, it remains uncertain whether acute, as opposed to chronic, exposure to alcohol at specified periods can also cause disruption in the neuronal population of the developing brain. This question was investigated by exposing Wistar rat pups to 7.5 g/kg body weight of ethanol administered as a 10% solution via an intragastric cannula over an 8 hour period either on the 5th (PND5) or the 10th (PND10) postnatal day of age. Gastrostomy controls received a 5% sucrose solution substituted isocalorically for the ethanol. Another set of pups raised by their mothers was used as “suckle controls”. All surgical procedures were carried out under halothane vapour anaesthesia. After the artificial feeding regimes, all pups were returned to the lactating dams and weaned at 21 days of age. Between 52 and 54 days of age, the rats were anaesthetised with an intraperitoneal injection with Nembutal and killed by intracardiac perfusion with 3% glutaraldehyde in 0.1 M phosphate buffer. The relatively unbiased stereological procedure known as the “fractionator” method was used to estimate the total number of Purkinje cells in the cerebellum of each animal. The Purkinje cell nucleolus was used as the counting unit; it was assumed that each Purkinje cell contained only one nucleolus. PND10 ethanol‐treated rats and gastrostomy and suckle controls had between about 210,000‐232,000 Purkinje cells in the cerebellum. However, the PND5 ethanol‐treated rats had only about 137,000 Purkinje cells. Two‐way analysis of variance procedures revealed significant main effects of age at time of alcohol exposure and groups as well as a significant interaction between them. It is concluded that the Purkinje cell population numbers can be disrupted by acute exposure to alcohol on the 5th, but not the 10th, postnatal day of age. © 1995

ISSN:0092-7317    

DOI:10.1002/cne.903600311

出版商:Wiley‐Liss, Inc.    

年代:1995

数据来源: WILEY