摘要:

AbstractIn this work we studied the effects of unilateral eye enucleation on the contents and distribution of leu‐enkephalin‐, met‐enkephalin‐arg6‐gly7‐leu8‐, and substance‐P‐like immunoreactivities (L‐ENK‐I, ENK‐8‐I, and SP‐I, respectively) in the superficial layers of the rat superior colliculus (SC) by means of the unlabelled antibody peroxidase‐antiperoxidase method. In the normal rat only a few L‐ENK‐I neurons appear dispersed in the stratum griseum superficiale. No immunostained somata appear in the stratum opticum. The most striking effect of unilateral enucleation was the dramatic appearance of a laminarly distributed population of L‐ENK‐I and/or ENK‐8‐I neurons in the dorsal stratum opticum of the SC contralateral to the enucleated side. This population of immunoreactive cells was observed with all the survival times examined in the present study (3, 7, 15, and 30 days) and was always accompanied by an increase in the immunostaining of L‐ENK‐I and/or ENK‐8‐I fibers in the contralateral stratum griseum superficiale. Enucleation also produced a decrease in the immunostaining of SP‐I dendrites that only became obvious 15 days after enucleation. However, the number of SP‐I somata or terminal‐like immunoreactive structures showed no detectable changes.These results show that retinal deafferentation of the superficial layers of the rat SC has different effects on some immunohistochemically distinguishable neuronal subgroups in the SC, suggesting different functional or trophic relati

ISSN:0092-7317    

DOI:10.1002/cne.902990402

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

年代:1990

数据来源: WILEY

摘要:

AbstractTo identify the galanin‐immunoreactive neurons projecting to the posterior lobe of the pituitary in the rat hypothalamus, a retrograde tracer (complex of wheat germ agglutinin‐enzymatically inactive horseradish peroxidase‐colloidal gold) was injected into the posterior lobe of the pituitary. Sections of the hypothalamus were treated with a combination of silver enhancement of retrogradely transported tracer and immunohistochemistry of galanin. Of the total number of hypothalamic cells doubly labeled with retrograde tracing and galanin‐immunostaining, 56–60% were found in the supraoptic nucleus, 18–23% in the retrochiasmatic nucleus, 8–10% in the lateral magnocellular portion of the paraventricular nucleus. The ratio of (number of doubly labeled cells/number of galanin‐immunoreactive cells) in each of the above regions was similar to the ratio of (number of retrogradely labeled cells/number of Nissl‐stained cells) in the supraoptic nucleus. Of all retrogradely labeled cells in the hypothalamus, 51–56% also contained galaninlike immunoreactivity.In conclusion: (1) galanin‐immunoreactive fibers in the posterior lobe of the pituitary originate mainly in the supraoptic nucleus, retrochiasmatic nucleus, and lateral magnocellular portion of the paraventricular nucleus, (2) most of galanin‐immunoreactive cells in these regions project to the posterior lobe of the pituitary, and (3) about half the neurons constituting the hypothalamo‐neurohypophyseal system contain gal

ISSN:0092-7317    

DOI:10.1002/cne.902990403

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe visual receptive field physiology and anatomical connections of the lateral intraparietal area (area LIP), a visuomotor area in the lateral bank of the inferior parietal lobule, were investigated in the cynomolgus monkey (Macaca fascicularis). Afferent input and physiological properties of area 5 neurons in the medial bank of the intraparietal sulcus (i.e., area PEa) were also determined. Area LIP is composed of two myeloarchitectonic zones: a ventral zone (LIPv), which is densely myelinated, and a lightly myelinated dorsal zone (LIPd) adjacent to visual area 7a. Previous single‐unit recording studies in our laboratory have characterized visuomotor properties of area LIP neurons, including many neurons with powerful saccade‐related activity. In the first part of the present study, single‐unit recordings were used to map visual receptive fields from neurons in the two myeloarchitectonic zones of LIP. Receptive field size and eccentricity were compared to those in adjacent area 7a. The second part of the study investigated the cortico‐cortical connections of area LIP neurons using tritiated amino acid injections and fluorescent retrograde tracers placed directly into different rostrocaudal and dorsoventral parts of area LIP. The approach to area LIP was through somatosensory area 5, which eliminated the possibility of diffusion of tracers into area 7a.Unlike many area 7a receptive fields, which are large and bilateral, area LIP receptive fields were much smaller and exclusively confined to the contralateral visual field. In area LIP, an orderly progression in visual receptive fields was evident as the recording electrode moved tangentially to the cortical surface and through the depths of area LIP. The overall visual receptive field organization, however, yielded only a rough topography with some duplications in receptive field representation within a given rostrocaudal or dorsoventral part of LIP. The central visual field representation was generally located more dorsally and the peripheral visual field more ventrally within the sulcus. The lower visual field was represented more anteriorly and the upper visual field more posteriorly. In LIP, receptive field size increased with eccentricity but with much variability within the sample.Area LIPv was found to have reciprocal cortico‐cortical connections with many extrastriate visual areas, including the parieto‐occipital visual area PO; areas V3, V3A, and V4; the middle temporal area (MT); the middle superior temporal area (MST); dorsal prelunate area (DP); and area TEO (the occipital division of the intratemporal cortex). Area LIPv is also connected to area TF in the lateral posterior parahippocampal gyrus. Although area LIPd has many of the same cortico‐cortical connections as LIPv, some differences were apparent. Area LIPd and not LIPv has connections with visual areas TEa and TEm (anterior and medial divisions of the intratemporal cortex) and with multimodal area IPa (subdivision of association cortex in caudal bank of superior temporal cortex) in the superior temporal sulcus. A topographic relationship between rostrocaudal parts of area LIP (including both LIPv and LIPd) and the lateromedial parts of prefrontal cortex across areas 8a (frontal eye fields) and the medial portion of area 46 was also apparent. Intrinsic connections of LIP with other areas in the inferior parietal lobule included a feedforward projection to area 7a and connections with the bimodal ventral intraparietal area (VIP) as well as with somatosensory area 7b (PF). Some retrogradely labeled cells were seen in area 5, but this projection was not confirmed by control injections placed in the medial bank of the intraparietal sulcus (area PEa). An interesting observation was that the input into areas PEa and LIP from parieto‐occipital visual areas (medial dorsal parietal area (blDPl and area PO) was found to be topographically organized such that MDP and the dorsal part of PO project to area PEa, while ventral PO and a few MDP neurons project to the opposite bank in LIP. This “visual” input to area PEa was also seen in single‐unit recordings in area 5 in wlhich a small number of visually responsive cells were identified Le., 7 of 204 neurons). All remaining neurons mapped in area 5 were highly responsive to joint position, movement, and/or touch.These anatomical and physiological data demonstrate that area LIP is a unique visual area in posterior parietal cortex, with histological, anatomical, and physiological properties different from other areas in the inferior parietal lobule. Analysis of feedforward and feedback projections suggests that area LIP occupies a high position in the overall hierarchy of extrastriate visual processing areas

ISSN:0092-7317    

DOI:10.1002/cne.902990404

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

年代:1990

数据来源: WILEY

摘要:

AbstractLateral‐to‐motor and medial‐to‐motor synapses in crayfish nerve cords are composed of an electrical and a chemical component. The presynaptic terminals showed localized clusters of synaptic vesicles, electron‐dense areas, coated pits, and coated vesicles. In thin sections, active zones were defined by electron‐dense regions where synaptic vesicles attached and, in freeze‐fracture replicas, by clusters of intramembrane particles localized in bands with vesicle openings on the sides of these bands.The cytoplasmic surface of the postsynaptic membrane opposite the active zones was coated with electron‐dense material that in freeze‐fracture replicas was seen as an increase in intramembrane particles located in the external leaflet (EF‐face). This specialization of the postsynaptic membrane may correspond to the neurochemical receptor. Also, pre‐ and postsynaptic membranes were separated by a wider extracellular gap than those of adjacent nonsynaptic regions and electrical synapses or gap junctions.Synaptic vesicles were located exclusively at the synaptic regions by means of a cytoskeleton that was different for the electrical and the chemical components. The vesicles associated with the electrical component were anchored to a cytoskeleton composed of a beaded layer of densities located parallel to the membrane. This cytoskeleton maintained the synaptic vesicles separated from the presynaptic membrane by a distance of 13 ± 2 nm. The synaptic vesicles associated with the chemical component were anchored to electron‐dense regions formed by filaments arranged in bundles, anchored to the presynaptic membrane. Vesicles lined both sides of the bundle of filaments in very close proximity to the presynaptic membrane, probably positioned to discharge their contents into the extracellular space and to replace

ISSN:0092-7317    

DOI:10.1002/cne.902990405

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

年代:1990

数据来源: WILEY

摘要:

AbstractDuring embryonic development of the rodent forebrain, a cavity normally appears at the midline just below the corpus callosum. This cavity, the cavum septi, is present in mice by gestational day 18, but is subsequently obliterated by growth of the septal nuclei and neuropil. After x‐irradiation of pregnant mice with 125r on gestational day 14.5, the cavum septi did not develop. This dramatic developmental abnormality was accompanied by delayed fusion of the septum, and a reduction in the population of subventricular cells that normally migrate to form a sling of cells extending from the medial aspect of the lateral ventricles to the midline. In normal animals formation of the cavum septi involves degeneration of this subcallosal sling of SV cells. Thus absence of the cavum after x‐irradiation may be due to the premature killing of subventricular cells before their migration toward the midl

ISSN:0092-7317    

DOI:10.1002/cne.902990406

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

年代:1990

数据来源: WILEY

摘要:

AbstractSpinal cord projections from lumbar dorsal root ganglia (DRGs) were investigated in adult rats following injections of choleragenoid horseradish peroxidase (B‐HRP) into each of the six lumbar DRGs. This method is known to label primarily thick fibers. Labeling was found in all laminae except in the outer part of lamina II. Labeled fibers and terminal‐like structures were found 8–13 segments rostral and 1–5 segments caudal to the injected DRGs.A somatotopic organization was revealed in laminae III, where the labeling seemed to be organized in mediolateral zones. Some of these protruded as fingerlike processes through segments rostral and caudal to the root entry level. An interdigitating pattern for these fingerlike processes was seen between some DRGs, while an extensive overlap was found between other DRGs. Many zones were found to correspond to the known central projections of peripheral sensory nerves supplied by the injected ganglion. This suggests that the central projection of a DRG is highly related to the projections of the peripheral nerves included in the DRG.The projections to lamina IV were organized in a similar manner as in lamina III, even though the projections showed a higher degree of overlap than in lamina III. No clear somatotopic organization was found in laminae V‐IX.Provided that the topographical relationship between central projections of single peripheral nerves and of DRGs correspond to their peripheral projections, the results of this study, together with results of earlier studies suggest that the outlines of dermatomes are highly related to the territories of peripheral nerves included in the d

ISSN:0092-7317    

DOI:10.1002/cne.902990407

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe principal relay nuclei of the thalamus receive their cholinergic innervation from two midbrain cholinergic groups: the pedunculopontine tegmental nucleus and the laterodorsal tegmental nucleus. The different thalamic nuclei exhibit populations of cholinergic axons which vary in density and morphology when examined at the light microscopic level. However, the ultrastructure of the cholinergic terminals in different thalamic nuclei has not been described. This study was undertaken to confirm that synaptic contacts are formed by cholinergic axons in several principal thalamic relay nuclei, to describe their ultrastructural morphology, and to identify the types of postsynaptic elements contacted by cholinergic synaptic terminals. The thalamic nuclei examined in this study are the dorsal lateral geniculate nucleus, ventroposteromedial nucleus, ventroposterolateral nucleus, and anteroventral nucleus.Our results confirm that cholinergic axons form synaptic terminals in these thalamic nuclei. Cholinergic synaptic terminals contact structures outside the characteristic synaptic glomeruli, are never postsynaptic, and have morphologies and postsynaptic targets which differ among the thalamic nuclei. In the ventroposterior nuclei, cholinergic terminals form asymmetric synaptic contacts onto larger dendrites in the extraglomerular neuropil. In the anteroventral nucleus, cholinergic terminals form both symmetric and asymmetric synaptic contacts onto dendrites and somata. Cholinergic terminals in the anteroventral nucleus are larger than those in other nuclei. In the dorsal lateral geniculate nucleus, cholinergic terminals contact both somata and dendrites in the extraglomerular neuropil, but the synaptic contacts in this nucleus are symmetric in morphology.

ISSN:0092-7317    

DOI:10.1002/cne.902990408

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe lateral geniculate nucleus of the thalamus sends efferents to the hypothalamic suprachiasmatic nucleus, which is involved in generation and entrainment of several circadian rhythms. It seems reasonable to believe that the lateral geniculate conveys visual information about the length of the photoperiod to the circadian oscillator. In order to study in more detail the topographical relationship between the lateral geniculate and the suprachiasmatic nucleus, anterograde tracing withPhaseolus vulgarisleucoagglutinin (PHA‐L) and retrograde tracing with wheatgerm agglutinin coupled to horseradish peroxidase (WGA‐HRP) were performed in the gerbil.After iontophoretic injections of PHA‐L in the lateral geniculate, a large number of PHA‐L‐immunoreactive fibers and nerve terminals were observed in the ventrolateral part of the suprachiasmatic nucleus. Nerve fibers were also present in the ventromedial and dorsolateral portions, particularly in the caudal half of the nucleus. PHA‐L‐immunoreactive nerve fibers continued outside the borders of the suprachiasmatic nucleus to the adjacent anterior hypothalamic, the periventricular, and the subparaventricular areas. A moderate number of fibers entered the lateral hypothalamic area and the tuber cinerum via the optic tract and chiasm. Moreover, the paraventricular nucleus, the supraoptic nucleus, the medial preoptic area, the lateral preoptic area, and the supramammillary nucleus contained a few labeled fibers. In all parts of the hypothalamus receiving an input from the lateral geniculate, fine beaded immunoreactive fibers with varicosities and nerve terminals were observed, some of which were found in close apposition to hypothalamic neurons. Only after labeling of neurons in the intergeniculate leaflet of the lateral geniculate nucleus, fibers were found in the hypothalamus. This topographical organization of the geniculohypothalamic pathway was supported by retrograde tracing after injections of WGA‐HRP in the suprachiasmatic area. In these experiments, retrograde labeled neurons were observed in the intergeniculate leaflet and, in agreement with the anterograde studies, most of labeling was observed in the ipsilateral side. These results confirm that the suprachiasmatic nucleus receives a substantial input from the intergeniculate leaflet of the lateral geniculate. Moreover, the present data demonstrate that the suprachiasmatic nucleus is not the only nucleus that receives a direct visual input. Thus other hypothalamic areas might be influenced by a direct rhythmic neurona

ISSN:0092-7317    

DOI:10.1002/cne.902990409

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

年代:1990

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902990401

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

年代:1990

数据来源: WILEY