摘要:

AbstractExcitatory amino acids (EAA) acting onN‐methyl‐D‐aspartate (NMDA), α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and kainate receptors play an important role in synaptic transmission in the spinal cord. Quantitative autordiography and physiological experiments suggest that NMDA receptors are localized mainly in lamina II while kainate and AMPA receptors are found on both dorsal and ventral horn neurons. However the cell types expressing EAA receptors and their laminar distribution is not known. We have used a cobalt uptake mentod to study the morphology and distribution of spinal cord neurons expressing AMPA, kainate, or NMDA excitatory amino acid receptors in the lumbar enlargement of the rat spinal cord. The technique involved superfusion of hemisected spinal cords of 14 day‐old rat pups in vitro with excitatory amino acid receptor ligands in the presence of CoCl2. Cobalt has been shown to enter cells through ligand‐gated ion channels in place of Ca2+. Cells which accumulated cobalt ions following activation by ionotropic excitatory amino acid receptors were visualised histochemically. The cobalt uptake generated receptors‐specific labeling of cells, as the NMDA receptor antagonist D‐(−)‐2‐amino‐(5)‐phosphonovaleric acid (D‐AP‐5) (20 μM) blocked the NMDA, but not kainte‐inducced cobalt uptake. The kainate‐induced cobalt labeling was reduced by the non‐selective excitatory amino acid receptor antagonist kynurenic acid (4 mM). Passive opening of the voltage‐gated Ca2+‐channel by KCI (50 mM) did not result in colbalt uptake, indicating that cobalt enters cells through ligand‐gated Ca2+‐channels.AMPA (500 μM), kainate (500 μM), or NMDA (500 μM) each induced cobalt uptake with characteristic patterns and distributions of neuronal staining. Overall, kainate induced cobalt uptake in the greatest number of neuronal perikarya while NMDA‐induced uptake was the lowest. AMPA and kainate, but not NMDA superfusion, resulted in cobalt labeling of glial cells.Our result show that the cobalt uptake technique is a useful way to study the morphology and distribution of cells expressing re

ISSN:0092-7317    

DOI:10.1002/cne.903440302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractNerve growth factor (NGF), a classic neurotropic factor, promotes neuronal survival, maintenance, regeneration and differentiation in the peripheral nervous system and parts of the central nervous system. NGF activity is mediated by cell surface bound receptors including the low affinity NGF receptor (LNGFr) which is expressed by some peripheral and central neurons and is present on peripheral nerve Schwann cells during development and regeneration.The olfactory system is a useful model for the study of the role of LNGFr in neuronal development and regeneration. The growth of olfactory axons into the brain begins in the embryo and continue through the first few postnatal weeks. In mature animals there is persistent turnover and generation of olfactory receptor neurons (ORNs) and continuous growth of new axons into the oflfactory bulb. These new axons grow along the preexisting olfactory pathway. In the mature olfactory system, LNGFr has been observed in the glomerular layer of the olfactory bulb, the target of ORNs. However, neither the cellular localization nor the development expression of LNGFr has been characterized. Her, we tested the hypothesis that LNGFr expression is developmentally regulated in the olfactory nerve and is reinduced following injury to the mature olfactory nerve.LNGFr‐immunoreactivity (IR) was first observed in the olfactory mucosa at embryonic day (E)13 and in the olfactory nerve at E14. LNGFr‐IR increased in the nerve during embryonic development, began to decrease at around postnatal day (P)5 and was scarcely detectable in normal adults. The staining patterns suggests that LNGFr is located on the olfactory nerve Schwann cells. Streaks of LNGFr‐IR were present in the adult olfactory nerve. We reasoned that these streaks might represent transient reexpression of LNGFr associated with normal olfactory neurons turnover and replacement. Consistent with this hypothesis, LNGFr was robustly reexpressed in the adult olfactory nerve following lesion of the olfactory epithelium.Starting late in development (E21) and in the adult, LNGFr‐IR was also observed on fibres in deep layers of the olfactory bulb. LNGFr‐IR was also observed in neurons of the nucleus of the diagonal band (NDB) in the basal forebrain. NDB is the sole source of cholingeric afferents of the olfactory bulb. Thus, we tested the hypothesis that LNGFr in the deep layers of the olfactory bulb is located on NDB axons by making lesions of NDB. Following the lesion, LNGFr‐IR disappeared in the deep layers of the olfactory bulb but remained in the glomerular layer.We conclude that LNGFr‐IR is associated with several distinct populations of cells in the olfactory system. This suggests that LNGFr‐IR plays several distinct functional roles in the olfactory system, including support of olfactory axon growth and regeneration and maintenance of cholinergic innervation of the olfactory bulb. © 1994

ISSN:0092-7317    

DOI:10.1002/cne.903440303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThis is a survey of the distribution, form, and proportion of neurons immunoreactive for gamma‐aminobutyric acid (GABA) or glutamic acid decarboxylase (GAD) in cat primary auditory cortex (AI). The cells were studied in adult animals and were classified with respect to their somatic size, shape, and laminar location, and with regard to the origins and branching pattern of their dendrites. These attributes were used to relate each of the GAD‐positive neuronal types to their counterparts in Golgi preparations.Each layer had a particular set of GABAergic cell types that is unique to it. There were 10 different GABAergic cell types in AI. Some were specific to one layer, such as the horizontal cells in layer I or the extraverted multipolar cells in layer II, while other types, such as the small and medium‐sized multipolar cells, were found in every layer.The number and proportion of GABAergic cells were determined by using postembedding immunocytochemistry. The proportion of GABAergic neurons was 24.6%. This was slightly higher than the values reported elsewhere in the neocortex. The laminer differences in density and proportion of GABAergic and non‐GABAergic neurons were also comparable (though somewhat higher) to those found in other cortical areas: thus, 94% of layer I cells were GABAergic, while the values in other layers ranged from 27% (layer V) to 16% (layer VI). Layer VI had the most heterogeneous population of GABAergic neurons.The proportion of these cells across different regions within AI was studied. Since some receptive field properties such as sharpness of tuning and aurality are distributed non‐uniformly across AI, these might be reflected by regional differences across the cerebral cortex. There were significantly more GABAergic somata in layers III and IV in the central part of AI, along the dorsoventral axis, where physiological studies report that the neurons are tuned most sharply (Schreiner and Mendelson [1990] J. Neurophysiol.64:1442–1459). Thus, there may be a structural basis for certain aspects of local inhibitory neuronal organization. © 1994 Wil

ISSN:0092-7317    

DOI:10.1002/cne.903440304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe form, density, and neuronal targets of presumptive axon terminals (puncta) that were immunoreactive for gamma‐aminobutyric acid (GABA) or its synthesizing enzyme, glutamic acid decarboxylase (GAD), were studied in cat primary auditory cortex (AI) in the light microscope. High‐resolution, plastic‐embedded material and frozen sections were used. The chief results were: (1) There was a three‐tiered numerical distribution of puncta, with the highest density in layer Ia, an intermediate number in layers Ib–IVb, and the lowest concentration in layers V and VI, respectively. (2) Each layer had a particular arrangement: layer I puncta were fine and granular (less than 1 μm), and layer V and VI puncta were mixed in size and predominantly small. (3) The form and density of puncta in every layer were distinctive. (4) Immunonegative neurons received, in general, many more axosomatic puncta than immunopositive cells, with the exception of the large multipolar (presumptive basket) cells, which invariably had many puncta in layers II–VI. (5) The number of puncta on the perikarya of GABAergic neurons was sometines related to the number of puncta in the layer, and in other instances it was independent of the layer. Thus, while layer V had a proportion of GABAergic neurons similar to layer IV, it had only a fraction of the number of puncta: perhaps the intrinsic projections of supragranular GABAergic cells are directed toward layer IV, as those of infragranular GABAergic neurons may be.Since puncta are believed to be the light microscopic correlate of synaptic terminals, they can suggest how inhibitory circuits are organized. Even within an area, the laminar puncta patterns may reflect different inhibitory arrangements. Thus, in layer I the fine, granular endings could contact preferentially the distal dendrites of pyramidal cells in deeper layers. The remoteness of such terminals from the spike initation zone contrasts with the many puncta on all pyramidal cell perikarya and the large globular endings on basket cell somata. Basket cells might receive feed‐forward disinhibition, pyramidal cells feed‐forward inhibition, and GABAergic non‐basket cells would be the target of only sparse inhibitory axosomatic input. Such arrangements imply that the actions of GABA on AI neurons are neither singular nor simple and that the architectonic locus, laminar position, and morphological identity of a particular neuron must be integrated for a more refined view of it role in cortical circuitry. © 1

ISSN:0092-7317    

DOI:10.1002/cne.903440305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe intergeniculate leaflet (IGL) in the rat is a distinctive subdivision of the lateral geniculate complex that participates in the regulation of circadian function through its projections to the circadian pacemaker, the suprachiasmatic nucleus (SCN) of the hypothalamus. The present investigation was undertaken to provide a precise definition of the IGL and a characterization of its neuronal organization including neuronal morphology, chemical phenotype, connections, and synaptic organization. The IGL extends the entire rostrocaudal lenght of the geniculate complex and contains a distinct population of small to medium neurons. In Golgi preparations, the neurons are multipolar with dendrites largely confined to the IGL. The neurons can be subdivided into three groups on the basis of neurotransmitter content and projections: (1) neurons that contain GABA and neuropeptide Y and project to the SCN; (2) neurons that contain GABA and enkephalin and project to the contralateral IGL; and (3) a small group of neurons that projects to the SCN but not characterized as yet by neurotransmitter content. The IGL receives dense, bilateral input from retinal ganglion cells and dense substance P input of unknown origin. A number of neurons in the anterior hypothalamic area and, particualrly, the retrochiasmatic area project to the IGL, and there are sparse projections from brainstem monoamine and cholinergic neurons. The synaptic organization of the IGL is complex with afferents terminating in glomerular complexes that include axoaxonic synapatic interactions. Virtually all IGL afferents synapse upon dendrites and spines, with the densest synaptic input occurring on the distal portions of the dendritic arbor. The organization of the IGL and its connections as revealed in this analysis is in accord with its role in the integration of visual input with other information to provide feedback regulation of the SCN integration of visual input with other information to provide feedback regulation of the SCN pacemaker. © 1994 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903440306

出版商:Wiley‐Liss, Inc.    

年代:1994

数据来源: WILEY

摘要:

Abstractα‐Amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA)‐type glutamate receptors are probably the most widespread excitatory neurotransmitter receptors of the central nervous system, and they play a role in most normal and pathological neural activities. However, previous detailed studies of AMPA subunit distribution have been limited mainly to the brain. Thus, a comprehensive study of AMPA receptor subunit distribution was carried out on sections of rat spinal cord and dorsal root ganglia, which were immunolabeled with antibodies made against peptides corresponding to C‐terminal portions of the AMPA receptor subunits: GluR1, GluR2/3, and GluR4. In the spinal cord. Labeling was most prominent in the superficial dorsal horn, motoneurons, and nuclei containing preganglionic autonomic neurons. Immunostaining also was observed in neurons in other regions including those known to contain Renshaw cells and Ia Inhibitory cells. Although overall immunostaining was lighter with antibody to GluR1 than with GluR2/3 and 4, there were neurons were neurons that preferentially stained with antibody to GluR1. These “GluR1 intense” neurons were usually fusiform and most concentrated in lamina X. In dorsal root ganglia, immunostaining of ganglion cell bodies was moderate to dense with antibody to GluR2/3 and light to moderate with antibody to GluR4. Possible neuroglia in the spinal cord (mainly GluR2/3 and 4) and satellite cells in dorsal root ganglia (GliR4) were immunostained. Electron microscopic studies of the the superficial dorsal horn and lateral motor column showed staining that was restricted mainly to postsynaptic densities and associated dendritic and cell body cytoplasm. In dorsal horn, colocalization of dense‐cored vesicles with clear, round synaptic vesicles was observed in unstained presynaptic terminals apposed to stained postsynaptic densities. Subsynaptic dense bodies (Taxi‐bodies) were associated with some stained postsynaptic densities in the superficial dorsal horn and lateral motor column. Based on several morphological features including vesicle structure and presence of Taxi‐bodies, it is likely that at least some of the postsynaptic staining seen in this study is apposed to glutamatergic input from primary sensory afferent termi

ISSN:0092-7317    

DOI:10.1002/cne.903440307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAs a catecholamine, depamine belogs to a class of molecules that have multiple transmitter and hhormonal functions in vertebrate and invertebrate nervous systems. However, in the lobster, where many central beurons have been identified and the peripheral innervation pattern is well known, the distribution of dopamine‐containing neurons has not been examined in detail. Therefore, immunocytochemical methods were used to identify neurons likey to contain dopamine and tyrosine hydroxylase in the central nervous system of the juvenile lobsterHomarus gammarus.Approximately 100 neuronal somata stain for the catecholamine and/or its synthetic enzyme in the brain and ventral nerve cord. The systems of neurons labeled with dopamine and tyrosine hydroxylase natibodies have the following characteristic: (1) the two systems are nearly identical; (2) every segmental ganglion contains at least one pair of labeled neurons; (3)the positions and numbers of cell bodies labeled with each antiserum are similar in the various segmental ganglia; (4) six labeled neurons are anatomically identified; two interneurons from the brain project within the ventral cord to reach the last abdominal ganglion, two neurons from the commissural ganglia are presumably neurosecretory neurons, and two anterior unpaired medial abdominal neurons project to the hindgut muscles; and (5) nocell bodies are labeled in the stomatogastric ganglion, but fibers and terminals in the neuropil are stained. The remarkably small numbers of labeled neurons and the presence of very large labeled somata with far‐reaching projections are distinctive features consistent with other modulatory aminergic systems in both vertebrates and invertebrates. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903440308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTouch doems are clearly delineated mechanoreceptors that are visible on the depilated skin of mammals. These structures consist of a sharply circumscribed disk of thickened epithelium surmounting a group of Merkel cells that are innervated by type I sensory neurons. These characteristic cutaneous structures provide an ideal opportunity for investigating whether the localization of nerve growth factor (NGF) in the skin related to sites of sensory axon termination. For these reasons, we have used immunocytochemistry to study the distribution of NGF and the low‐affinity NGF receptor (p75NGFR) in the touch domes of adult rat skin. Intense NGF‐like immunoreactivity was sharply restricted to keratinocytes (excluding the stratum corneum) of the thickened epidermis of the touch domes. The epidermis immediately surrounding touch domes and the epidermis of the tylotrich hair follicle associated with touch domes were immunonegative for NGF but were immunopositive for p75NGFRas werer the type I nerve endings innervating these cells. Quantitative Northern blotting revealed that the level of NGF mRNA was substantially higher in keratinocytes isolated from the stratum granulosum and stratum spinosum than in keratinocytes isolated from the stratum germinativum. These findings indicate that NGF synthesis in mature skin has a highly restricted regional distribution that is primarily associated with the innervation of a specialized touch receptor. © 1994 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903440309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903440301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY