摘要:

AbstractThis study was designed to examine the sequential changes in the developing granuloprival cerebellar culture. In this model of anomalous cerebellar development, organotypic cultures derived from newborn Swiss‐Webster mice were exposed to the DNA synthesis inhibitor, cytosine arabinoside, at explantation and were fixed for electron microscopic examination on successive days in vitro. Similar developmental stages were compared in control explants. Granule cell destruction began early, and was widespread by 2 days in vitro, when oligodendrocyte destruction also began in treated cultures. A few granule cells survived, but no recognizable oligodendrocytes remained by 7 days in vitro, at a time when myelin was initially evident in control explants. Purkinje cell recurrent axon collateral sprouting began at 3 days in vitro in cultures exposed to cytosine arabinoside, and the sprouted terminals initially synapsed with Purkinje cell somata, somatic spines and dendritic shafts. Synapses with Purkinje cell dendritic spines developed later, at approximately the same time as parallel fiber‐Purkinje cell dendritic spine synapses formed in control cultures. Astrocytic ensheathment of control Purkinje cells was well underway by 6 days in vitro and Purkinje cell somata were relatively rounded and almost completely ensheathed by 9 days in vitro. Glial ensheathment did not occur in cytosine arabinoside treated cultures, and Purkinje cell somata were scalloped at 7 days in vitro by excess impinging recurrent axon collateral terminals, and never developed the smooth contours characteristic of control Purkinje cells. Purkinje cell somatic spines persisted in treated explants, and reduction of excess extracellular space was delayed until 12 days in vitro, when most‐of the developmental changes had been completed. The earlier development of synapses by excess recurrent axon collateral terminals with Purkinje cell somata, somatic spines and dendritic shafts, followed by the later development of heterotypical synapses with dendritic spines, in parallel with synapse formation by normal presynaptic elements, suggests that the sequence of development of synapses is a function of the maturational state of the postsynaptic compo

ISSN:0092-7317    

DOI:10.1002/cne.903130202

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractLesioning the vagus nerve in the neck (cervical vagotomy) results in a rapid and virtually complete loss of motoneurons in the dorsal motor nucleus of the vagus in neonatal rats. The present study sought to determine whether access to gastric target tissue will promote the survival of these motoneurons after axotomy. Quantitative analysis demonstrate that subdiaphragmatic vagotomy, which leaves the cut vagal axons in close proximity to their normal gastric targets, results in significantly less motoneuron loss than cervical vagotomy. Furthermore, the loss of motoneurons after cervical vagotomy can be significantly reduced by transplanting embryonic gastric tissue to the neck of vagotomized neonatal host rats, in the vicinity of the cut axons. The survival effect of transplanted gastric tissue appears specific because control‐transplants of embryonic bladder tissue fail to reduce motoneuron death after cervical vagotomy. Injections of the neural tracers Fluoro‐Gold and cholera toxin‐horseradish peroxidase into gastric transplants labeled surviving motoneurons in cervically vagotomized rats, whereas tracer injections into bladder transplants or into host cervical tissues did not. These results indicate that neonatal vagal motoneurons are capable of making the adjustments necessary to survive axotomy if they have access to gastric target cells. The apparent dependence of injured neonatal vagal motoneurons on gastric tissue offers a new system in which to examine in vivo the trophic interactions between neurons and their ta

ISSN:0092-7317    

DOI:10.1002/cne.903130203

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe distribution of neurons and fibers containing calcitonin‐gene‐related peptide (CGRP) was mapped in the thalamo‐telencephalic auditory pathways of four amniote species, rats, pigeons (Columba livia), caiman (Caiman crocodilus), and turtles (Pseudemys scripta). In colchicine‐treated turtles and pigeons, numerous CGRP+ perikarya were observed in the auditory relay nucleus of the thalamus (n. reuniens of reptiles, and n. ovoidalis of birds). In pigeons, these neurons were most abundant in the outer circumference of the nucleus and were not observed without colchicine pretreatment. In the telencephalon of turtles, caiman, and pigeons, CGRP + fibers were observed within portions of the dorsal ventricular ridge previously shown to receive projections from the auditory thalamus, thus implying that the thalamic CGRP+ neurons observed here in fact project to these telencephalic areas. In colchicine treated rats, numerous CGRP+ perikarya were observed along the ventral margin of the medial geniculate nucleus extending into the posterior intralaminar and peripeduncular nuclei, as well as occasionally within the ventral subdivision of the medial geniculate nucleus. Injections of fluorogold into the auditory cortex combined with immunofluorescence labeling for CGRP revealed that CGRP+ cells in these areas do, in fact, project to the auditory c

ISSN:0092-7317    

DOI:10.1002/cne.903130204

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractAuditory nerve fibers have been subdivided into three functional groups (Liberman, M.C. [1978] J. Acoust. Soc. Am.63:442–455) differing in acoustic sensitivity and spontaneous discharge rate (SR). Using intracellular injection of horseradish peroxidase, the present study analyzes the projections of these three neuronal subclasses to the various subdivisions of the anteroventral cochlear nucleus (AVON) and to the different cell types found therein. The average number of swellings and number of cells contacted decreased from low‐ to medium‐ to high‐SR groups. However, these differences in terminal elaboration were not evenly distributed throughout the AVCN. The small cell cap was almost exclusively innervated by low‐ and medium‐SR fibers, i.e., those with the highest acoustic thresholds. Within anterior AVCN, spherical‐cell innervation was seen from all SR groups, whereas almost all multipolar cell innervation was from low‐ and medium‐SR fibers. In the posterior AVCN, multipolar‐cell innervation was equally likely from all SR groups, whereas globular cells were preferentially contacted by high‐SR fibers. These SR‐based trends in cochlear nucleus innervation help explain some of the known physiological properties of cell‐types in each subdivision. They also suggest that additional physiological study of the small cell cap may be key in elucidating the functional significance

ISSN:0092-7317    

DOI:10.1002/cne.903130205

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe dendritic morphology of cells in the lateral superior olivary nucleus was studied with the Golgi method in adult and postnatal ferrets. The lateral superior olivary nucleus in the adult ferret is a convoluted structure with an M‐shape in frontal sections. The major cell type appears to have disk‐shaped dendritic trees. Most dendritic trees appear to be approximately orthogonal to the curved medial‐lateral axis of the nucleus. Depending on their position in the limb and on the plane of section with respect to the dendritic tree, the disk‐shaped cells are either bipolar or radiate in orientation. One subclass of disk‐shaped cells has secondary dendritic branches that end as tufts of tendril‐like processes. In a second subclass of cells, the dendrites exhibit several orders of dichotomous branching and lack obvious tufts of terminal processes. Marginal cells are observed at the border of the nucleus and have dendrites restricted to the margins of the cell plate.The bipolar orientation of disk‐shaped cells orthogonal to the axis of the limbs is already apparent by the time of birth. Transient spines and other appendages are abundant on somata and dendrites during the first postnatal week. By the end of the first postnatal month only distal appendages are found. Tufts of fine tendril‐like processes appear at the ends of dendrites between postnatal

ISSN:0092-7317    

DOI:10.1002/cne.903130206

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractA quantitative taxonomy of primate striatal neurons was elaborated on the basis of the morphology of Golgi‐impregnated neurons. Dendritic arborizations were reconstructed from serial sections and digitized in three dimensions by means of a video computer system. Topological, metrical, and geometrical parameters were measured for each neuron. Groups of neurons were isolated by using uni‐ and multidimensional statistical tests. A neuronal species was defined as a group of neurons characterized, quantitatively by a series of nonredundant parameters, differing statistically from other groups, and appearing as a separate cluster in principal component analysis. Four neuronal species were isolated: (1) the spiny neuronal species (96% of striatal neurons) characterized by spine‐free proximal dendrites (up to 31 μm) and spine‐laden distal dendrites, which are more numerous, shorter, and less spiny in the human than in the monkey, (2) the leptodendritic neuronal species (2%) characterized by a small number of long, thick, smooth, and sparsely ramified dendrites, (3) the spidery neuronal species (1%) characterized by very thick dendritic stems and a large number of varicose recurrent distal processes, and (4) the microneuronal species (1%) characterized by numerous short, thin, and beaded axonlike processes. All striatal neurons give off a local axonal arborization.The size and shape of cell bodies were analyzed quantitatively in Golgi material and in materials treated for Nissl‐staining, immunohistochemical demonstration of parvalbumin and histochemical demonstration of acetylcholinesterase. Only three types were distinguishable: small, round cell bodies corresponding to either spiny neurons or microneurons, medium‐size elongated cell bodies, which were parvalbumin‐immunoreactive and corresponded to leptodendritic neurons, and large round cell bodies, which were acetylcholinesterase‐positive and corresponded to spidery neurons. Thorough analysis of previously elaborated classifications revealed that spidery neurons do not exist in rats and cats and that large cholinergic neurons in these species correspond to leptodendritic neurons. From this, it can be assumed that the dendritic domain of striatal cholinergic neurons is considerably smaller in primates than in other species.Computer simulations based on both the frequency of each neuronal species and their three‐dimensional dendritic morphology revealed that the striatum consists of two intertwined dendritic lattices: a fine‐grain lattice (300–600 μm) formed by the dendritic arborizations of spiny, spidery, and microneurons, and a large‐grain lattice (1,200 μm) formed by the dendritic arborizations of leptodendritic neurons. This suggests that cortical information can be processed in the striatum through two different systems: a fine‐grain system that would conserve the precision of the cortical input, and a large‐g

ISSN:0092-7317    

DOI:10.1002/cne.903130207

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractWe used the autoradiographic tract‐tracing method to define the amygdaloid projection fields after injecting3H‐amino acids into individual thalamic nuclei in the rat. The parvicellular division of the ventroposterior nucleus, the thalamic taste relay, projected lightly to the central and lateral amygdaloid nuclei. The central medial, interanteromedial, and paraventricular thalamic nuclei, viscerosensory relays of the thorax and abdomen, projected heavily to the amygdala. All projected to the basolateral amygdaloid nucleus, the paraventricular nucleus in addition having terminations in the central nucleus, the amygdaloid portion of the nucleus of the stria terminalis, and the amygdalohippocampal transition area. The magnocellular division of the medial geniculate, a thalamic auditory (and, to a moderate degree, a spinothalamic) relay, sent heavy projections to the central, accessory basal, lateral, and anterior cortical nuclei, and to the anterior amygdaloid area and the nucleus of the accessory olfactory tract. Other thalamic nuclei projecting to the amygdala, for which functions could not be associated, were the paratenial and subparafascicular nuclei. The former projected to the lateral, basal, and posterolateral cortical nuclei; the latter projected very lightly to the central, medial, and basal accessory nuclei. These results show that, like the cortical amygdaloid nuclei, which are sensory (olfactory) in nature, the subcortical amygdaloid nuclei must have major sensory functions.These thalamic afferents, when correlated with cortical and brainstem data from the literature, suggested that the amygdala is in receipt of sensory information from many modalities. To uncover the manner by which such information is processed by the amygdala and relayed to effector areas of the brain, six hypothetical mechanisms relating to modality specificity and convergence were posited. By charting sensory‐related afferents to all subdivisions of the amygdala, each nucleus was characterized as to its mechanism of information processing. Four proposed amygdaloid systems emerged from this analysis. A unimodalcorticomedialamygdaloid system relays pheromonal information from the accessory olfactory bulb to medial basal forebrain and hypothalamic areas. A second system—thelateral‐basomedial—collects and combines input from a number of sensory modalities and distributes it to the same basal forebrain and hypothalamic areas as the corticomedial. The central system appears to concentrate the effect of viscerosensory information arriving from multiple brainstem, thalamic, cortical, and amygdaloid sources; this information is combined with significant auditory and spinothalamic inputs from the thalamus and cortex. The central system projects to lateral nuclei in the basal forebrain, hypothalamus, and brainstem. The final system—thebasolateral—is a unimodal relay of viscerosensory information from the thalamus to the central nucleus of the amygdala and to the lateral basal forebrain. We argue that all sensory information sorted and restructured by the amygdala to form these systems is distributed directly or indirectly (via a synapse in the basal forebrain or hypothalamus) to diverse brainstem effector mechanisms, an expansion of Nauta's ('58) limbic midbrain concept. The final relays of the first two systems are to motor mechanisms in the medial midbrain and brainstem tegmentum; those of the second two systems project more laterally in the midbrain and brainstem tegmentum. The functional properties of the lateral and medial brainstem areas are quite different.Functional evidence suggests that the four amygdaloid circuits may act in concert as channels by which social communications or other stimuli of behavioral significance initiate sequences of species‐typical consummatory behaviors. Together, they appear to form an integrated neural system of emotion, which can operate independent of the corticobulbar/ cor

ISSN:0092-7317    

DOI:10.1002/cne.903130208

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe NADPH‐d histochemical method stains a selective population of neurons in the central nervous system. Although the functional significance of the enzyme in these cells is unknown, it has nonetheless proved to be a useful marker. In the present study we describe the distribution of NADPH‐d‐positive cells and fibers in the amygdaloid complex of theMacaca fascicularismonkey.NADPH‐d‐positive neurons were distributed throughout the amygdaloid complex. Based on the intensity of the reaction product, three different types of NADPH‐d positive cell were described: type 1 cells, the most intensely stained, varied in morphology and were most commonly found in the accessory basal, basal, and lateral nuclei and in the nucleus of the lateral olfactory tract; type 2 cells, the most common NADPH‐d‐positive cells, were more lightly stained, were generally stellate in shape, and were found in the lateral, basal, and accessory basal nuclei; type 3 cells were very lightly stained, oval or round in shape, and mostly found in the medial, anterior cortical, and paralaminar nuclei.NADPH‐d staining was also associated with axonal fiber plexuses in various regions of the amygdala. The highest densities of stained fibers were found in the lateral nucleus, the parvicellular portion of the accessory basal nucleus, and the anterior amygdaloid area. The lowest densities of NADPH‐d‐positive fiber staining were found in the amygdalohippocampal area, in the lateral part of the central nucleus, and in the intercalated nuclei. In addition to the neuronal and fiber staining, a diffuse, blue neuropil staining was also observed, most commonly in the anterior cortical nucleus, the medial nucleus, the intercalated nuclei, and especially in the amygdalohippocampal area. The distribution of NADPH‐d staining often respected nuclear boundaries within the amygdala and was particularly helpful in clarifying the borders of the a

ISSN:0092-7317    

DOI:10.1002/cne.903130209

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractGABA‐synthesizing neurons were identified in the medulla of the rat by peroxidase‐antiperoxidase (PAP) immunohistochemistry for glutamic acid decarboxylase (GAD). Using diaminobenzidine (DAB) either alone or intensified with silver, a relatively large number of GAD‐immunoreactive neurons were evident within the reticular formation, raphe nuclei and vestibular nuclei. In all these areas, profuse GAD‐immunoreactive varicosities appeared to contact the soma and dendrites of both non‐GABA and GABA neurons. These observations suggest that GABA neurons may act as interneurons or local projection neurons within the medulla and accordingly exert a potent inhibitory and/or disinhibitory control on bulbar projection neurons.Within the ventral reticular formation (pars alpha and ventralis of the gigantocellular reticular field) and raphe magnus, large numbers of prominent GAD‐immunoreactive neurons resembled in size and morphology and overlapped in distribution the serotonin‐immunoreactive neurons of the same regions. However, by sequential double immunostaining utilizing DAB as a chromogen for serotonin (5‐HT) and benzidine dihydrochloride (BDHC) for GAD, it was found that GAD‐containing neurons were distinct from 5‐HT‐containing neurons.Following injections of wheat germ agglutinin conjugated to horseradish peroxidase (WGA‐HRP) into the upper cervical spinal cord and combined processing for WGA‐HRP (using tetramethylbenzidine [TMB] with cobalt) and immunohistochemistry (with DAB), a contingent of spinally projecting neurons were found to contain GAD. The GAD‐immunoreactive reticulo‐and raphe‐spinal neurons were most frequent within the pars alpha and ventralis of the gigantocellular reticular fields and the raphe magnus, where they were approximately equal in number to the coexistent, but distinct 5‐HT spinally projecting neurons. GABA neurons of the medulla may thus contribute directly to the bulbar inhibitory influence upon

ISSN:0092-7317    

DOI:10.1002/cne.903130210

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY

摘要:

AbstractThe topographical relationship between Ruffini endings and the surrounding collagen fibers in the periodontal ligament of hamster incisors was investigated by means of both immunohistochemistry for neurofilament protein (NFP) and electron microscopy. Periodontal Ruffini endings, a type of stretch receptor, were present exclusively in the alveolar half of the periodontal ligament. Their axon terminals were densely and regularly associated with transverse collagen fibers, possibly forming a mechanoreceptive complex. Since blood sinuses with frequent anastomoses extended throughout the alveolus‐related part, the densely innervated collagen bundles were separated from each other by the vascular spaces. Electron microscopic observation of specimens stained with tannic acid revealed a linkage between the axon terminals of the Ruffini endings and the surrounding collagen filaments. The axon terminals were enveloped by multiple layers of the basal lamina, which were penetrated by collagen filaments. The irregularly arranged collagen filaments were sandwiched between electron‐dense laminae of the multilayered basal lamina. The possible mechanism of mechanoreception by the periodontal Ruffini endings is discussed on the basis of the immunohistochemical and ultrastructural findi

ISSN:0092-7317    

DOI:10.1002/cne.903130211

出版商:Wiley‐Liss, Inc.    

年代:1991

数据来源: WILEY