摘要:

AbstractAn antibody to glutamate decarboxylase has been used in a light and electron microscopic study of the neostriatum of rats that had received intracerebral injections of colchicine. In the light microscope, neuronal perikarya and small punctate structures that displayed immunoreactivity were found. The perikarya could be divided into two classes based on their sizes: small‐to‐medium‐sized and large. Proximal dendrites, axon initial segments, and axon collaterals were occasionally stained. When the nuclei of the neurons were visible, they possessed indentations. The immunoreactive punctate structures were spread evenly throughout the neostriatum but occasionally were associated with immunoreactive and nonimmunoreactive perikarya.When the same sections were examined in the electron microscope, the small‐to‐medium‐sized immunoreactive perikarya were found to be similar in morphology and synaptic input to a class of Golgi‐impregnated neuron that has been previously shown to accumulate locally administered, radiolabelled γ‐aminobutyric acid. Neurons with the ultrastructural characteristics of typical striatonigral neurons did not display immunoreactivity. As neurons in this pathway probably contain γ‐aminobutyric acid, it is possible that our procedure or our antibody does not stain all γ‐aminobutyric‐acid‐containing structures in the neostriatum.A total of 404 immunoreactive punctate structures were examined by correlated light and electron microscopy or by electron microscopy alone. They were identified as immunoreactive axonal boutons and each of them, when examined in serial sections, displayed typical synaptic specialisations. Membrane specialisations were always of the symmetrical type. At least five distinct targets of the immunoreactive terminals were identified: (1) neurons that were themselves immunoreactive for glutamate decarboxylase; the immunoreactive terminals made synaptic contact with all parts of the neurons examined, i.e., perikarya, proximal dendrites, and axon initial segments. (2) Neurons identified by Golgi impregnation of the same sections as medium‐sized and densely spiny; the immunoreactive terminals made contact predominantly with the perikarya and dendritic shafts. (3) Large neurons found only in the ventral caudate‐putamen, whose somata and dendrites were ensheathed in immunoreactive terminals. (4) Medium‐sized nonimmunoreactive perikarya that possessed nuclear indentations. (5) Large nonimmunoreactive perikarya that had the typical structural features of striatal cholinergic neurons.It is concluded that there is a diverse innervation of many types of striatal neuron by synaptic terminals that possess the ability to synthesize γ‐aminobutyric acid and that these terminals probably arise

ISSN:0092-7317    

DOI:10.1002/cne.902370102

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe organization of hypothalamic projections to the cerebral cortex in the rat has been studied using retrograde and anterograde tracer methods. Four separate populations of hypothalamic neurons, which constitute a major source of diffuse cortical innervation, were identified:Tuberal lateral hypothalamic (LHAt)neurons which innervate the cerebral cortex tend to cluster in the perifornical region, in the zona incerta, and along the medial edge of the cerebral peduncle, at levels roughly coextensive with the ventromedial hypothalamic nucleus. Most of these neurons project to the ipsilateral cortex; a small percentage innervate the contralateral cortex, but this varies among cortical terminal fields. The perifornical neurons are organized in a roughly topographic medial‐to‐lateral relationship with respect to their cortical terminal fields.Field of Forel (FF)neurons, which project primarily to the frontal cortex of the ipsilateral hemisphere, are located just ventral to the medial edge of the medial lemniscus, at the level of the ventromedial basal thalamic nucleus. The more laterally placed neurons innervate the lateral frontal, insular and perirhinal cortex; the more medial neurons, around the mammillothalamic tract, innervate the medial frontopolar, prelimbic, infralimbic, and anterior cingulate cortex.Posterior lateral hypothalamic (LHAp)neurons form a dense cluster spanning the lateral hypothalamus, from the cerebral peduncle to the posterior hypothalamic area at premammillary levels, and extending into the supramammillary nucleus and the adjacent ventral tegmental area. LHAp neurons innervate the entire cerebral cortex, predominantly on the ipsilateral side. Populations of LHAp neurons projecting to different cortical target areas show considerable spatial overlap, but computer plots of the centers of these populations demonstrate a strict topographic relationship with respect to the cerebral cortex.Tuberomammillary (TMN)neurons form a sheet along the ventrolateral surface of the premammillary hypothalamus. About twice as many TMN neurons innervate the ipsilateral, as compared to the contralateral hemisphere; it is not known whether single neurons project to both hemispheres. No topographic organization of the TMN cortical projection is apparent.Injections of different‐colored fluorescent dyes into various cortical areas demonstrate that hypothalamic neurons in general have rather restricted cortical terminal fields. Only occasional neurons are found, primarily in LHAt, which are double labeled by injections into different cytoarchitectonic areas.Anterograde tracing of fibers from LHAp, with the aid of the autoradiographic method, demonstrated two efferent pathways to cerebral cortex: amedialpathway runs through the medial forebrain bundle, traverses the diagonal band and medial septal nuclei, and enters the fornix and the cingulate bundle, from which it distributes to the hippocampal formation and to medial cortical fields, respectively. Thelateralpathway runs through the lateral part of the medial forebrain bundle, then turns laterally through the substantia innominata to enter the external capsule, from which it distributes to lateral cortical fields. LHAp fibers in the hippocampus primar‐ ily innervate the outer part of the dentate granule cell layer; there is also a lighter projection to the CA2 and CA3a fields. In the neocortex, the densest LHAp innervation is in layer V and the deep part of layer VI, adjacent to the internal capsule. There is more sparse innervation also of layers I and 111. TMN fibers distribute in a similar, though much less dense, distr

ISSN:0092-7317    

DOI:10.1002/cne.902370103

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe extent to which transplants of embryonic cortical tissue can be used to replace damaged cortical projections has been examined. Embryonic entorhinal cortex was implanted into the entorhinal region of young adult rats that had previously received a lesion through the angular bundle. Projections between transplant and host were examined by using WGA‐HRP and the fluorescent dye Fast Blue. Implants selectively innervated areas of the host hippocampus and amygdala which normally receive entorhinal afferents. Implants were innervated by cells in the host diagonal band and, in one case, by cells in the contralateral entorhinal and/or presubicular cortex. In most cases, host fibers were differentially distributed within transplants, possibly reflecting an ability of host fibers to recognize and selectively innervate their appropriate targets even though the cellular organization of the implant is different from that present during normal development. These data suggest that homotypic implants of embryonic entorhinal cortex can, in some ways, replace severed cortical projections and may eventually be able to reconstituve normal cortical circuitr

ISSN:0092-7317    

DOI:10.1002/cne.902370104

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractVagal afferent projections, and preganglionic parasympathetic neurones contributing to the vagus nerve in golden hamsters were traced following application of horseradish peroxidase (HRP) to the proximal end of the cervical or abdominal nerve stump. Efferents in the cervical vagus were traced to their perikarya of origin in the dorsal motor nucleus (DMN) of the vagus, the commissural gray of the cervical spinal cord, the nucleus ambiguus, the nucleus of the accessory spinal nerve (NASN), and in the ventral horn dorsolateral to the NASN. Perikarya in the NASN and the region dorsolateral to it did not contribute efferent fibres to the abdominal vagus. In the remaining cell groups, fewer labelled perikarya were labelled in the abdominal cases than in the cervical cases. Extraperikaryal labelling (presumptive terminals) in the cervical cases was seen primarily in the nucleus of the solitary tract. A modest distribution of extraperikaryal grains was also noted along the inner rim of the area postrema and the ventral border of the DMN. Anterograde labelling was sparser and had a more restricted distribution in the abdominal cases. A detailed description of brainstem pathways of vagal efferent and afferent fibres is provided, as is a comparison of the present observations with those in similar studies of other species.

ISSN:0092-7317    

DOI:10.1002/cne.902370105

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThree extrathalamic subcortical inputs to the part of the cerebral cortex that is known to receive thalamic fibers in the turtle were examined in the present study. Direct projections from the locus coeruleus, the superior medial raphe nucleus, and a wide area of the basal telencephalon that lies ventromedial to the globus pallidus were demonstrated with the horseradish peroxidase method. Fluorescence histochemistry confirmed the presence of catecholamine‐containing fibers in the rostral half of dorsal cortex and also demonstrated a dense network of serotoninergic fibers. Biochemical analysis showed the concentration of both monoamines to be relatively high; the norepinephrine concentration was 709 ng/g and the serotonin concentration was 1,750 ng/g. No evidence was found to suggest the existence of either a dopamine fiber projection to cortex comparable to that of mammalian neocortex or the presence of an epinephrine pathway to turtle cortex equivalent to the epinephrine‐containing fibers in the pallium of amphibians. The coexistence of the projections from the thalamus with (1) noradrenergic projections from the locus coeruleus, (2) serotoninergic projections from the superior medial raphe nucleus, and (3) presumably cholinergic projections from the basal telencephalon provide at least four distinct subcortical inputs to the reptilian dorsal cortex. Neither thalamic nor similar extrathalamic inputs have been demonstrated in the dorsal pallium of amphibia. Mammalian neocortex, in contrast, has even more elaborately differentiated inputs of both types. These results support the idea that thalamic and extrathalamic inputs to cortex appear at the same time in vertebrate evolution, and that both types of inputs are required for the normal development and function of neocor

ISSN:0092-7317    

DOI:10.1002/cne.902370106

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe callosal connections of the superior parietal lobule, area 5 of Brodmann, were studied in macaque monkeys (M. nemestrinaandM. fascicularis) using anatomical techniques based on both anterograde and retrograde axoplasmic transport of wheat‐germ‐agglutinin‐conjugated horseradish peroxidase. From sagittal sections, two‐dimensional flattened computer reconstructions of the volumes of cortical tissue containing callosal‐projecting neurons (callosal efferent zone) and/or callosal terminal axons (callosal terminal territory) were obtained. Callosal zones were found in area 5, including the supplementary sensory area, in a limited part of area 6, i.e., in the supplementary motor area, in area 7b, in the cortex of the dorsal bank of the sylvian fissure, and in a limited part of area 7a, in the cortex of the upper third of the rostral bank of the superior temporal sulcus. Callosal neurons in all cortical areas studied, though with regional variations, predominated in layer IIIb, but were also very numerous in layers VI and V. They were rare in other cortical laminae. In the cortical regions projecting heterotopically to area 5, the tangential distribution of callosal neurons was discontinuous because of the presence of large acallosal regions. These were not observed in area 5, although here the distribution of callosal neurons waxed and waned in the tangential cortical plane. Callosal axons to and/or from area 5 crossed the midline in the posterior, presplenial part of the corpus callosum. In the superior parietal lobule they terminated in radial patches or columns, spanning layers I–IV. These columns of various width (200–2,000 μm) were separated by gaps of similar size, free of such terminals. Callosal neurons were present not only within, but also between, the callosal terminal columns. Callosal neurons located within the callosal terminal columns were, in a statistically significant, way, more numerous than those located between them. The callosal efferent zone occupied 71% of the tangential domain of area 5, whereas the callosal terminal territory occupied only 49% of it. This difference is statistically significant. The discontinuous columnar arrangement of callosal terminals and the periodic distribution of callosal neurons in the lateral part of area 5 defined three main bands of callosal connections of irregular shape which were oriented mediolaterally and ran parallel to the main architectonic borders, the border between areas 2 and 5 and that b

ISSN:0092-7317    

DOI:10.1002/cne.902370107

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractImmunohistochemical methods have been used to chart the distribution of rat hypothalamic growth‐hormone‐releasing factor (rhGRF) immunoreactivity in the brains of normal and colchicine‐treated adult albino rats. The results suggest the existence of at least two distinct rhGRF‐containing systems: one responsible for delivery of the peptide to portal vessels in the median eminence, and one whose relationship, if any, to hypophysiotropic function is less direct. A dense plexus of rhGRF‐stained fibers was found throughout the external lamina of the median eminence that is the route by which the peptide is delivered to the anterior pituitary. This projection appears to arise primarily from a group of rhGRF‐immunoreactive neurons centered in the arcuate nucleus. Some 1,000–1,500 rhGRF‐positive neurons were counted on each side of the brain in rats pretreated with colchicine. Colocalization studies, using a sequential double staining technique, indicated that a subset of rhGRF‐immunoreactive neurons in the arcuate region contain neurotensin immunoreactivity. No evidence was obtained for colocalization of rhGRF with either of two pro‐opiomelanocortin‐derived peptides (α‐melanocyte‐stimulating hormone, adrenocorticotropic hormone (1–24)) in individual neurons in the arcuate nucleus. Much smaller groups of neurons were localized in the parvicellular division of the paraventricular nucleus of the hypothalamus and in the dorsomedial nucleus, and it is unclear whether they contribute to the plexus of rhGRF‐stained fibers in the median eminence.The only other region in the rat brain in which rhGRF‐stained cells were found reliably was in the area that roughly encapsulates the caudal aspect of the ventromedial nucleus of the hypothalamus. Because cells in this region are not known to project to the median eminence, they may be assumed to contribute to the extrahypophysiotropic rhGRF‐stained projections outlined below. From the level of the arcuate and ventromedial nuclei, rhGRF‐immunoreactive fibers could be traced along the base of the brain and through the periventricular system to discrete terminal fields limited almost exclusively to the hypothalamus and adjoining parts of the basal telencephalon. All parts of the periventricular region of the hypothalamus receive an input, including the preoptic and anterior parts in which somato‐statin‐containing neurons that project to the median eminence are clustered. Other prominent terminal fields were localized in discrete parts of the dorsomedial, paraventricular, suprachiasmatic, and premammillary nuclei, and in the medial preoptic and lateral hypothalamic areas. Beyond the hypothalamus, sparse projections have been traced to parts of the limbic region of the telencephalon, including the lateral septal nucleus, the bed nucleus of the stria terminalis, and the medial nucleus of the amygdala. No rhGRF‐immunoreactive cells or fibers have been detected in the neocortex, in any structure caudal to the mammillary complex of the hypothalamus, in the spinal cord, or in a number of peripheral tissues.These results suggest that GRF displays the most restricted distribution of the known hypophysiotropic hormones of the hypothalamus. The possibil‐ ity that the central rhGRF system may comprise an integrated unit for the control of growth hormone secr

ISSN:0092-7317    

DOI:10.1002/cne.902370108

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractDamage to the rat septohippocampal pathway results in the growth of sympathetic axons from nearby blood vessels into the denervated hippocampal formation. Sympathohippocampal sprouting exhibits lesion specificity‐that is, only injury to the septohippocampal projection elicits the sprouting response. Whether other perivascular fibers sprout in response to septohippocampal injury (response specificity) has been addressed in the present study. Using cathecholamine histofluorescence and acetylcholinesterase histochemical techniques, we determined the distribution and incidence of perivascular sympathetic and nonsympathetic fibers associated with para‐hippocampal blood vessels in normal rats and in rats sustaining medial septal lesions. We found that sympathetic fibers are more numerous than acetylcholinesterase‐positive fibers at all septotemporal levels of the hippocampal formation and that both types are very rare at dorsal hippocampal levels in normal rats. Following medial septal lesions, however, there is a tremendous increase in the number of perivascular sympathetic fibers at dorsal hippocampal levels but no change in the number of acetylcholinesterase‐positive fibers. Electron microscopic observations indicate that the increase in perivascular fibers is due to increases in the number of sympathetic axonal fascicles as well as the number of axons per fascicle. Furthermore, both light and electron microscopic data suggest that parahippocampal veins are normally not accompanied by perivascular fibers but are associated with sympathetic fibers following medial septal lesions. These results indicate that sympathetic sprouting in response to septohippocampal denervation exhibits specificity not only in terms of the lesion which elicits such sprouting but also in terms of the types of fibers that respond to the

ISSN:0092-7317    

DOI:10.1002/cne.902370109

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractWe report on the anatomy and physiology of three fusiform cells in the dorsal cochlear nucleus (DCN) of the cat. The extra‐ and intracellular responses of these cells to pure tones showed features typical of the cell type. Peristimulus time histograms (PSTHs) were usually of the pauser or buildup configuration with chopping behavior noted in certain instances. Intracellular records during stimulus presentations revealed sustained depolarizations for the duration of the tone followed by a prolonged after‐hyperpolarization (AHP). On rare occasions, a hyperpolarization corresponding to the pause region of the PSTH was noted. Occasionally, a stimulus‐induced depolarization would be maintained after stimulus offset. Rebound excitation was also observed after the AHP. Morphologically, all three cells showed the standard fusiform cell features at the light microscopic level. The cell body gave rise to apical and basal dendritic trees. The apical tree branched frequently and displayed numerous spines distally. The basal tree had fewer branches and fewer, more irregular appendages. The axon originated from the cell body and gave rise to one or more collaterals before leaving the nucleus via the dorsal acoustic stria (DAS). At the electron microscopic (EM) level, the axon collaterals may terminate on a variety of cell types in the DCN, including fusiform cells. Their vesicles are round and the terminals closely resemble many unlabeled terminals seen on the cell body and apical and basal dendrites of our labeled fusiform cells. Terminals containing round vesicles, believed to be eighth nerve terminals, were found, with one exception, only on the basal dendrites. The spine‐laden, distal apical dendrites received primarily terminals containing round vesicles, presumed to originate from the unmyelinated axons of granule cells. The cell body and unmyelinated initial segment received mostly terminals containing pleomorphic and flat vesicles, which also made up a large percentage of the dendritic input. Some relevant correlations, between the distribution of synaptic terminals and the observed physiology, may be p

ISSN:0092-7317    

DOI:10.1002/cne.902370110

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902370101

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY