摘要:

AbstractThe ciliated dendritic bulb of the olfactory neuron of the bullfrog was studied with the electron microscope, with emphasis on microtubular elements. Methods used included various fixation procedures with and without detergent extraction, serial sectioning, microtubule polarity assays, and an assay to demonstrate F‐actin. Structural continuity exists, via microtubules, between the ciliary membrane and the perikaryon of the neuron. One type of structural link connects the distal end of the basal body to the plasma membrane and, in slightly oblique cross sections of the basal body, the link shows a highly characteristic tripartite profile resembling a claw hammer. The six to ten basal bodies of a dendritic bulb have a lateral foot that serves as an organizing center for microtubules, and these microtubules (totaling about 150) extend toward the perikaryon in the basal half of the epithelium. Polarity assays indicate that the attached or minus ends of dendritic microtubules are in the dendritic bulb, with their plus or fast‐growing ends near or within the perikaryon of the neuron. It is shown that dendritic microtubules are depolymerized by direct osmium tetroxide fixation, in contrast to olfactory axonal microtubules, which persist after such fixation. F‐actin appears to be abundantly present in the dendritic bulb of the neuron, and it is possible that this actin could play a role in shape changes of the dendrite. The various findings provide new information about the olfactory dendrite, its microtubule organizing centers, and the nature and relationships of its microtu

ISSN:0092-7317    

DOI:10.1002/cne.902420202

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe afferent projections from the prosencephalon to the mediodorsal thalamic nucleus (MD) were studied in the cat by use of the method of retrograde transport of horseradish peroxidase (HRP).Cortical and subcortical prosencephalic structures project bilaterally to the MD. The cortical afferents originate mainly in the ipsilateral prefrontal cortex. The premotor, prelimbic, anterior limbic, and insular agranular cortical areas are also origins of consistent projections to the MD. The motor cortex, insular granular area, and some other cortical association areas may be the source of cortical connections to the MD. The subcortical projections originate principally in the ipsilateral rostral part of the reticular thalamic nucleus and the rostral lateral hypothalamic area. Other parts of the hypothalamus, the most caudal parts of the thalamic reticular nucleus, the basal prosencephalic structures, the zona incerta, the claustrum, and the entopeduncular and subthalamic nuclei are also sources of projections to the MD.Distinct, but somewhat overlapping areas of the prosencephalon project to the three vertical subdivisions of MD (medial, intermediate, and lateral). The medial band of the MD receives a small number of prosencephalic projections; these arise mainly in the caudal and ventral parts of the prefrontal cortex. Cortical projections also arise in the infralimbic area, while subcortical projections originate in the medial part of the rostral reticular thalamic nucleus and lateral hypothalamic area. The intermediate band of the MD receives the largest number of fibers from the prosencephalon. These arise principally in the intermediate and dorsal part of the lateral and medial surface of the prefrontal cortex, the premotor cortex, and the prelimbic and agranular insular areas. Projections also originate in basal prosencephalic formations (preoptic area, Broca's diagonal band, substantia innominata, and olfactory tubercle), rostral reticular thalamic nucleus, and lateral hypothalamic area. A large number of prosencephalic structures also project to the lateral band of the MD. These are mainly the most dorsal and caudal parts of the lateral and medial surface of the prefrontal cortex, the premotor and motor cortices, and the prelimbic, anterior limbic, and insular areas. Projections arise also in the lateral rostral and caudal parts of the reticular thalamic nucleus, the zona incerta, the lateral and dorsal hypothalamic areas, the claustrum, and the entopeduncular nucleus.These and previous results demonstrate a gradation in the afferent connections to the three subdivisions of the MD. Brain structures related to the olfactory sensory modality and with allocortical formations of the limbic system project principally to the medial band of the MD. The intermediate band of the MD receives subcortical and cortical projections from structures mainly related to the limbic system and cortical regions related to sensory association cortices. The lateral band of the MD receives projections mainly originating in structures related to complex sensory associative processes and to the motor system (especially from brainstem and cortical structures implicated in the regulation of eye movements).

ISSN:0092-7317    

DOI:10.1002/cne.902420203

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractAlthough the auditory cortex is believed to be the principal efferent target of the medial geniculate body (MG), our recent behavioral studies indicate that in rats the conditioned coupling of emotional responses to an acoustic stimulus is mediated by subcortical projections of the MG. In the present study we have therefore used WGA‐HRP as an anterograde and retrograde axonal marker to (1) define the full range of subcortical efferent projections of the MG; (2) identify the cells of origin within the MG of each projection; and (3) determine whether the subregions of the MG that project to subcortical areas receive inputs from acoustic relay nuclei of the midbrain, particularly the inferior colliculus.The rat MG was first parcelled into three major cytoarchitectural areas: the ventral, medial, and dorsal divisions. The suprageniculate nucleus, located within the body of the MG just dorsal to the medial division, was also identified.Efferent projections of the MG were determined by combined anterograde and retrograde tracing methods. Injections of WGA‐HRP in the MG produced anterograde transport to cortex and several subcortical areas, including the posterior caudate‐putamen and amygdala, the ventromedial nucleus of the hypothalamus, and the subparafascicular thalamic nucleus. The cells of origin of the subcortical projections were then mapped retrogradely after injections in the anterogradely labeled areas. Injections in the caudate‐putamen or amygdala retrogradely labeled the medial division of the MG and the suprageniculate nucelus, as well as several adjacent areas of the posterior thalamus surrounding the MG. In contrast, injections in the ventromedial nucleus of the hypothalamus or the subparafascicular thalamic nucleus only produced labeling in the areas surrounding MG.Afferents to MG from the inferior colliculus were then identified. The central nucleus of the inferior colliculus, the main lemniscal acoustic relay nucleus in the midbrain, was found to project to the ventral and medial divisions of the MG. In contrast, the dorsal cortex and external nucleus of the inferior colliculus project to each division of the MG and to several additional nuclei in adjacent areas of the posterior thalamus.These data demonstrate that the medial division of MG, the suprageniculate nucleus, and immediately adjacent areas of the posterior thalamus provide a direct linkage between auditory neurons in the inferior colliculus and subcortical areas of the forebrain and thereby support the view that thalamic sensory nuclei relay afferent signals to subcortical as well as cortica

ISSN:0092-7317    

DOI:10.1002/cne.902420204

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe organization of the olfactory nerve projection to the olfactory bulb was studied immunohistochemically in the rabbit by using monoclonal antibodies (MAbs). Out of 42 MAbs raised against the homogenate of the olfactory bulb, two types of MAbs that strongly stained the olfactory nerve fibers (axons of olfactory receptor cells) were selected and their staining patterns were analysed in detail. MAbs of one type (represented by MAb R2D5) specifically labeled all olfactory receptor cells in the nasal epithelium and all olfactory nerve fibers and their terminal portions in the bulb.The other type of MAbs (represented by MAb R4B12) recognized only a subgroup of olfactory nerve fibers. The R41312‐positive fibers were distributed over the ventrolateral areas but not in the dorsomedial areas of the epithelium. Similarly in the bulb, the R41312‐positive fibers terminated in the glomeruli in the ventrolateral and the caudal regions but not in the dorsomedial region. These results demonstrate for the first time the cellular heterogeneity among olfactory receptor neurons at the molecular level. The segregated distribution of the subtypes of olfactory receptor cell axons both in the epithelium and the bulb indicates a defined topographical organization of the olfactory nerve projection. These results also suggest a functional division between dorsomedial and ventrolateral areas both in the epithelium and the b

ISSN:0092-7317    

DOI:10.1002/cne.902420205

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe neuronal architecture of the ventrobasal complex (VB) in dog is examined in coronal and horizontal brain sections processed by Golgi‐ and Nissl‐staining methods. Presumed projection and intrinsic neurons are identified by differences in soma size and shape, dendritic branch pattern, the morphology and distribution of appendages, and the appearance of axons. Forty‐five projection neurons are examined by quantifying (1) soma cross‐sectional area, (2) dendritic field extent and shape, (3) appendages on the soma, primary dendrites, and in a defined major dendritic branch zone, and (4) location in the VB. When considered independently, each variable offers little evidence for separation into morphological classes. However, several of the variables have wide ranges and show significant correlation with other parameters. Using the multivariate descriptive methods of principal components analysis and cluster analysis, a separation of the projection neurons into three morphological classes designated as large, medium, and small neurons is indicated. The features most critical in distinguishing between the groups are, in descending order of importance: (1) dendritic field extent; (2) number of primary dendrites; (3) soma cross‐sectional area; (4) number of appendages per major branch point (MBP); (5) number of appendages on the soma; and, (6) number of appendages on the primary dendrites. Dendritic field shape and neuron location have little influence in determining class

ISSN:0092-7317    

DOI:10.1002/cne.902420206

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractExtracellular, iontophoretic injections of horseradish peroxidase (HRP) were made directly into the cat's retina. The retinas were processed with the cobalt‐enhanced diaminobenzidine method and prepared as whole mounts. These retinas reveal HRP‐filled axons that extend widely and terminate within the inner plexiform layer. The axons are morphologically distinct from ganglion and amacrine cell dendritic trees that were retrogradely labelled from the same injection sites.The axons are long and straight, approximately 1 μm in diameter, and in some cases can be traced for several millimeters in the inner plexiform layer. Each axon gives rise to many short, terminal branches that extend, on average, 100 μm from the parent axon and bear clusters of boutons. The terminal branches are widely spaced so that the bouton clusters are distributed in small, isolated patches along the length of the axon. Bouton clusters vary in size and contain from two to over 100 loosely arranged boutons. Single boutons are frequently large, up to 3 μm in diameter.In one case a terminal axon was traced to its origin from the parent axon of an HRP‐filled ganglion cell. It is suggested, therefore, that these axons are intrinsic to the retina and originate as primary collaterals of gangli

ISSN:0092-7317    

DOI:10.1002/cne.902420207

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractSpecific thalamic afferents to visual areas 17 and 18 were physiologically classified as X or Y type and injected with horseradish peroxidase (HRP). The axons were examined under the light microscope and were then processed for correlated electron microsocpy. X axons arborised in area 17 and in the border between area 17 and 18. The X axons all formed terminals throughout layer 6, but were heterogeneous in their distribution in layer 4. They either occupied the entire width of sublayers 4A and 4B or were strongly biased toward layer 4A. Y axons also arborised in layers 4 and 6, but in area 17 they did not form boutons in sublamina 4B. Some Y axons projected only to area 18; others branched and arborised in both areas 17 and 18. Only the collaterals of one X axon were found to enter area 18; all the others were restricted to area 17. Y axons formed three to four separate patches of boutons about 300–400 μm in diameter, while all but one X axon formed a single elongated patch. Y axons had thicker main branches (3–4 μm) than X axons (1.5–2.5 μm) at their point of entry to the cortex. The main axon trunks and their medium‐calibre collaterals were myelinated, but the preterminal segments were unmyelinated and studded with boutons. Each X or Y axon contacted about seven to ten somata, but Y axons made more contacts per soma (three to six) than did X axons (two to three). In addition to somatic synapses, both X and Y axons formed asymmetric (type 1) synapses on dendritic spines and shafts, with spines forming the most frequent targets (80%). Each Y bouton made, on average, 1.64 synapses in area 17 and 1.79 synapses in area 18, whereas each. X bouton made only 1.27 synapses on average. Although there are proportionally fewer Y axons than X axons entering area 17, the Y axons provide as many synapses as the X axons because of their larger arbors and multisynapt

ISSN:0092-7317    

DOI:10.1002/cne.902420208

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

摘要:

AbstractThe precise location of physiologically identified specific afferent input on the different types of cell in the visual cortex and the identification of the neurotransmitters of these cells are essential to a better understanding of the first stage of cortical processing. A combination of anatomical, neurochemical, and physiological methods was used to identify the cortical neurones that receive synaptic input from X‐ and Y‐type afferents, which are thought to originate from cells of the lateral geniculate nucleus. One method relied on chance contacts made between single physiologically characterised axons, which had been injected with horseradish peroxidase (HRP), and the processes of cells impregnated by the Golgi method. These experiments revealed that both X and Y axons formed synapses on the dendrites of spiny stellate cells in layer 4. Y axons in both areas 17 and 18 established multiple synaptic contacts on basal dendrites of layer 3 pyramidal cells. One X axon contacted the apical dendrite of a layer 5 pyramidal cell and one Y axon contacted the dendrite of a large cell with smooth dendrites in layer 3. The maximum number of synapses made between one axon and a single postsynaptic cell was eight, although in most cases it was only one. It was concluded that one axon only provides a small fraction of the geniculate afferent input to an individual cell.A second method revealed that the somata in layer 4 in synaptic contact with the HRP‐filled axon terminals were GABA‐immunoreactive, and therefore might be involved in inhibitory processes. From light microscopic data it was found that somata receiving contacts from X axons in area 17 were significantly smaller (average diameter 15μm) than those contacted by the Y axons in areas 17 and 18 (average diameter 24 μm). Somatic contacts were extremely rare in layer 6. These data show that the X and Y afferents may activate separate subsets of inhibitory

ISSN:0092-7317    

DOI:10.1002/cne.902420209

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902420201

出版商:Alan R. Liss, Inc.    

年代:1985

数据来源: WILEY