摘要:

AbstractGamma‐aminobutyric acid (GABA) neurons intrinsic to the lamprey spinal cord are known to modulate synaptic transmission from interneurons active during locomotion and from mechanosensory dorsal cells. Many of these physiological effects are presynaptic. To establish the morphological substrates for these axo‐axonic interactions, an ultrastructural analysis was performed with an antiserum to fixed GABA. The GABA immunoreactivity (ir) was detected by postembedding peroxidase‐antiperoxidase and immunogold techniques. GABA‐ir terminals were found to make appositions with unlabelled axons located in the dorsal columns and in the ventrolateral aspect of the spinal cord. In the ventrolateral part of the cord, similar appositions between different GABA‐ir terminals were also observed. The immunolabelled terminals contained spherical to pleomorphic synaptic vesicles, and also glycogen granules and dense core vesicles. In some cases, the fine structure of the contacts between immunogold‐labelled terminals and unlabelled axons suggested a synaptic relationship. Such a relation was found in a relatively small proportion (2–3%) of the appositions studied. These specializations were always observed in close relation to an output synapse of the postsynaptic axon. It is suggested that the axo‐axonal contacts described may provide an effective modulation of the synaptic transmission from axons in the lamprey spinal cord. © 1993

ISSN:0092-7317    

DOI:10.1002/cne.903280402

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe ampullary electroreceptors on the trunk ofKryptopterus bicirrhisare induced and continuously maintained by a trophic substance released by their afferent nerve fibers. When the fibers are transected and the proximal stumps deflected to a new place, the regenerating fibers grow along new routes to the old electroreceptor sites and again induce organs there. The new routes consist of two sections. The first goes from the deflected stump end to other nearby running intact or degenerated nerves and fibers. In the second section, the regenerating fibers grow along these nerves and fibers to their distal ends, i.e., to the old electroreceptor sites. If the path‐guiding nerves and fibers are experimentally removed, the displaced fibers grow to the normal receptor areas directly. Growing out from the displaced stump, they spread out over the trunk in a pattern similar to the pattern displayed formerly by the original nerve fibers at this place. It is concluded that the outgrowing fibers do not possess a specificity for a certain receptor site or skin area, but spread out according to epigenetic factors in the periphery. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903280403

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

年代:1993

数据来源: WILEY

摘要:

AbstractThis work aims at a better understanding of the organization of the brain ofOctopus vulgaris, emphasizing the touch and visual learning centers. We injected the carbocyanine dye, DiI, into the cerebrobrachial connectives and, separately, into the brachial nerves of living octopuses. In both experiments, retrogradely transported granules of DiI appeared in motor neurons in the superior buccal, posterior buccal and subvertical lobes and in a hitherto unsuspected motor nucleus of several hundred neurons in the posterior dorsal basal and median basal lobes.In addition we labeled afferent fibers by injecting DiI into the caudal (sensory) division of the cerebrobrachial connective on one side; the label spread throughout the superior buccal, posterior buccal and the lateral and median inferior frontal lobes mainly on the injected side. It extended through the cerebral tract into the subvertical lobe, into the superior frontal lobe through the interfrontal tract, through the posterior buccal commissure into the opposite posterior buccal lobe and into the median inferior frontal lobe.The work suggests a new function for the posterior dorsal and median basal lobes, which are shown for the first time to project through the inferior frontal lobe system into the brachial nerves. In addition it represents the first full report of the successful use of the carbocyanine dyes DiI and DiO for labeling nerve tissue in a live invertebrate animal. © 1993 Wiley‐Liss, I

ISSN:0092-7317    

DOI:10.1002/cne.903280404

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

年代:1993

数据来源: WILEY

摘要:

AbstractDespite increased recognition of the importance and heterogeneity of astrocyte functions throughout the central nervous system (CNS) relatively little attention has been paid to morphological diversity among astrocytes. Recent studies have indicated that subsets of astrocytes are involved in glial‐axonal interactions critical to both development and reinnervation of the rat olfactory bulb. Here, we have characterized the morphologies and distribution of astrocytes within anatomically and functionally distinct layers of the adult main olfactory bulb (MOB).Using a known immunohistochemical marker for astrocytes, glial fibrillary acidic protein (GFAP), and the classic gold sublimate method, we identified six astrocyte subtypes based on their morphology and distribution: (1)unipolar, (2)irregular, (3)wedge‐shape, (4)circular, (5)semicircular, and (6)elongate. Unipolar, irregular and wedge‐shape astrocytes have not been previously described in the CNS. The unipolar and irregular types are located exclusively in the olfactory nerve layer. Wedge‐shape astrocytes are unique to, and are the major subtype in, the glomerular layer. These three morphologically unique astrocyte subtypes may correspond to olfactory nerve layer (ONL) and glomerular layer (GL) astrocytes, which express molecules that regulate axonal growth or synaptogenesis during development and/or regeneration of the olfactory nerve.In the glomerular layer, astrocytes are highly organized with respect to the glomeruli. Individual astrocytes are loyal to a single glomerulus. In the external plexiform layer, astrocytes are spaced relatively uniformly. In the granule cell layer, astrocytes appear to compartmentalize granule cell aggregates, recently shown to be coupled by tight junctions. The distribution and patterns of astrocyte processes and the density of GFAP immunoreactivity are distinctive for each of the layers of the olfactory bulb. The spacing of astrocytes and the organization of their processes may be important to compartmentalization of neuronal functions. High levels of GFAP immunoreactivity correlated with layers of high neuronal plasticity.The morphological diversity and differential distribution of astrocytes in the olfactory bulb reported here support growing evidence for functional diversity of astrocytes and important interactions among specific astrocyte and neuron subtypes. It is reasonable to hypothesize, therefore, that as for neurons, morphologically distinctive astrocyte subtypes may correspond to functionally specific classes. © 1993 Wiley

ISSN:0092-7317    

DOI:10.1002/cne.903280405

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe cytoarchitecture of nuclei in the preoptic area, ventral thalamus, dorsal thalamus, epithalamus, hypothalamus, posterior tuberculum, synencephalon, and pretectum and the accessory optic nuclei was analyzed in the clupeomorph teleost,Clupea harengus. Plesiomorphic (evolutionarily primitive) and apomorphic (evolutionarily derived) features of nuclei were identified by cladistic analysis. Plesiomorphic features include the cytoarchitectonic organization of most of the preoptic nuclei, the somewhat scattered cells of nucleus ventrolateralis, the compact, oval shape of nucleus intermedius, the presence of dorsoventrally oriented laminae in the central posterior nucleus, and most features of the hypothalamic nuclei. Also plesiomorphic are the presence of a thick, prominent paraventricular organ, a nucleus of the paraventricular organ, a nucleus tuberis posterior, and a preglomerular complex in which the boundaries between multiple nuclei are relatively difficult to distinguish. Additionally, the cytoarchitecture of the three synencephalic nuclei present inClupea, the presence of small cells in nucleus pretectalis superficialis pars parvicellularis and of larger, scattered cells in nucleus pretectalis superficialis pars magnocellularis, the presence of large cells in the dorsal accessory optic nucleus that form a rostrocaudally oriented column, and the feature of a small, cell‐sparse ventral accessory optic nucleus are plesiomorphic. Apomorphic features include the presence of a single, large, circular lamina that surrounds a central neuropil in all but the most caudal part of nucleus anterior, a lack of bilateral asymmetry in the habenular nuclei, the relatively small size of the periventricular nucleus of the posterior tuberculum, the presence of two, distinguishable caudomedial nuclei in the posterior tuberculum, elongation and folding of the neuropil of nucleus pretectalis superficialis pars parvicellularis, and the relatively large size of nucleus pretectalis superficialis pars magnocellularis and the posterior pretectal nucleus. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903280406

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe pattern of retinofugal projections to nuclei in the diencephalon and to the optic tectum was analyzed with horseradish peroxidase and autoradiographic methods inClupea harengus, a clupeomorph teleost, for comparison with osteoglossomorph, elopomorph, and euteleost teleosts and with non‐teleost actinopterygians. Most retinal fibers decussate in the optic chiasm and project to nuclei in the preoptic area, ventral and dorsal thalamus, posterior tuberculum, synencephalon, and pretectum, as well as to the accessory optic nuclei and optic tectum. Some ipsilateral projections do not decussate in the optic chiasm, while others decussate and recross via the supraoptic (minor) and posterior commissures. The pattern of projections is similar to that seen in other actinopterygian fishes with several exceptions. The terminal field usually present lateral to nucleus anterior in the dorsal thalamus is extremely reduced despite the relatively large size of the nucleus. A dense terminal field lies within the cell plate of nucleus corticalis in the pretectum rather than dorsal to it. The tectal hemisphere is composed of two distinct lobules, and the dorsal optic tract projects to the more rostromedial lobule while the ventral optic tract projects to the more caudolateral lobule. The lack of a significant projection to nucleus anterior and the lobular morphology of the optic tectum appear to be apomorphic forClupea. Other features of the pattern of retinal projections are also analyzed in actinopterygian fishes includingClupea, and several hypotheses are advanced as to which traits are plesiomorphic for actinopterygians and/or for teleosts. © 1993 Wiley‐Liss,

ISSN:0092-7317    

DOI:10.1002/cne.903280407

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

年代:1993

数据来源: WILEY

摘要:

AbstractTo analyze the local circuitry of the sympathetic ganglion, the synaptic relations of the neuronal processes of the principal neurons in the rat superior cervical ganglion were investigated by correlated light and electron microscopy combined with intracellular injection of biocytin. Intracellular iontophoresis of biocytin followed by avidin‐biotinylated horseradish peroxidase cytochemistry allowed complete visualization of the neuronal processes of the principal neurons. The stained principal neurons have a single process (axon), which leaves the ganglion, and several intraganglionic processes (dendrites), some of which show specific terminal arborizations. Some terminals of the dendritic collaterals formed pericellular plexuses or intercellular glomerular plexuses. Electron microscopically, the dendrites and their collaterals contain numerous small vesicles. Synaptic membrane specializations were observed between the stained dendritic collaterals and unlabeled neurites. These may be both preganglionic axon terminals and processes of principal neurons. The likely direction of neurotransmission often could not be determined because of the bidirectional synaptic structures. Our findings show that the dendritic collaterals of principal neurons appear to make both post‐ and presynaptic contacts with both the principal neurons and the preganglionic axons. It is suggested that the principal neurons might participate in local circuits involving not only preganglionic axons but also neighboring principal neurons. © 1993 Wiley‐Lis

ISSN:0092-7317    

DOI:10.1002/cne.903280408

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

年代:1993

数据来源: WILEY

摘要:

AbstractSelective35S‐labeled oligonucleotide probes were designed to sequences of the rat alpha‐2A (RG20), alpha‐2B (RNG), and alpha‐2C (RG10) adrenoreceptor mRNAs for use in in situ hybridization experiments on sections of unfixed rat brain, spinal cord and kidney. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each probe and region of the central nervous system were observed. Alpha‐2A mRNA labeling was most pronounced in neurons in layer six of the cerebral cortex, hypothalamic paraventricular nucleus, reticular thalamic nucleus, pontine nuclei, locus coeruleus, vestibular nuclei, trapezoid nuclei, deep cerebellar nuclei, nucleus tractus solitarii, ventrolateral medullary reticular formation, and the intermediolateral cell column of the thoracic spinal cord. In some of these locations, the receptor mRNA, in all probability, is present in noradrenaline and perhaps adrenaline neurons. The alpha‐2B probe, which primarily labels the kidney, gave only a very light signal in the thalamus in the central nervous system after extended exposure times. Alpha‐2C mRNA labeling was primarily observed in the olfactory bulb, cerebral cortex, islands of Calleja, striatum, hippocampal formation, cerebellar cortex, and dorsal root ganglia. Labeling patterns disappeared when excess unlabeled probes were added to their respective radiolabeled probes, or when sense probes were employed. When a hybrid antisense probe homologous to all three alpha‐2 probes was used, labeling patterns also disappeared. The present study therefore justifies the pharmacological subclassification of alpha‐2 receptors by providing anatomical evidence for specific and selective cell groups in the rat central nervous system containing mRNA for three alpha‐2 receptor subtypes. ©

ISSN:0092-7317    

DOI:10.1002/cne.903280409

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

年代:1993

数据来源: WILEY

摘要:

AbstractThere is evidence that foetal body movements first occur at 6 weeks gestation, and that the reflex arc is functional at 8 weeks. This correlates with the detection of the sensory neuropeptides calcitonin gene‐related peptide (CGRP) and substance P (SP) in spinal cord at 10 weeks gestation. However, the development of cutaneous neuropeptide‐containing nerves is not well documented in humans. We have investigated the early appearance and distribution pattern of CGRP, SP, vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), as well as those of the general neuronal marker protein gene product 9.5 (PGP) in various areas of foetal skin at different gestational ages. PGP‐immunoreactive nerves were first seen in the subepidermal plexus at 6 weeks gestational age. Initially, the immunoreactive nerves are thick, club‐shaped and distributed in the superficial dermis. Beaded adult‐like fibres become more numerous only at later ages (10–12 weeks), and extend from this plexus to penetrate the epidermis. Histologically, the skin of the hand develops faster than that of other body areas and at 9 weeks, more PGP‐immunoreactive nerves were seen in the palm than in the dorsum. Primitive sweat glands were first noted in axillary skin at 17 weeks, accompanied by a few PGP‐immunoreactive nerves. Occasional, small CGRP‐immunoreactive fibres were first noticed in the dermis at 7 weeks, but it was at 17 weeks that the presence of this neuropeptide was unequivocal in the subepidermal plexus. Sparse VIP‐, SP‐ and NPY‐immunoreactive fibres were not found until 16–17 weeks gestation, when they were seen in the dermis and around small blood vessels. These results show that development of nerves containing sensory neuropeptides precedes that of autonomic fibres, and that the former are present in developing cutaneous innervation after neuronal protein markers are detectable. The timing of the appearance of CGRP immunoreactivity in the skin correlates with that of the peptide in spinal cord, which is consistent with the reported reflex movements of the foetus. The morphological and functional development of cutaneous neuronal elements shows a close correlation that might provide some insight into the process of nerve regeneration in adult ski

ISSN:0092-7317    

DOI:10.1002/cne.903280410

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

年代:1993

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.903280411

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

年代:1993

数据来源: WILEY