摘要:

AbstractDynorphin facilitates conditioned place aversion and reduces locomotor activity through mechanisms potentially involving direct activation of target neurons or release of catecholamines from afferents in the nucleus accumbens. We examined the ultrastructural substrates underlying these actions by combining immunoperoxidase labeling for dynorphin 1–8 and immunogold silver labeling for the catecholamine synthesizing enzyme, tyrosine hydroxylase (TH). The two markers were simultaneously visualized in single coronal sections through the rat nucleus accumbens. By light microscopy, dynorphin immunoreactivity was seen as patches of immunoreactive varicosities throughout all rostrocaudal levels of the nucleus accumbens. The dynorphin‐immunoreactive terminals identified by electron microscopy ranged from 0.2 to 1.5 μm in cross‐sectional diameter, contained numerous small (30–40 nm) clear vesicles, as well as one or more large (80–100 nm) dense core vesicles. From the dynorphin‐immunoreactive terminals quantitatively examined in single sections, 74% (173/370) showed symmetric synaptic junctions mainly with large unlabeled dendrites. Of the dynorphin‐immunoreactive terminals forming identifiable synapses, approximately 30% contacted more than one dendritic target. In addition, single dendrites frequently received convergent input from more than one dynorphin‐labeled terminal. Irrespective of their dendritic associations, dynorphin‐immunoreactive terminals also frequently showed close appositions with other axons and terminals; these included unlabeled (41%), TH‐labeled (10%) or dynorphin‐labeled axons (14%). In contrast to dynorphin‐immunoreactive terminals, TH‐labeled terminals formed primarily symmetric synapses with small dendrites and spines or lacked recognizable specializations in the plane of section analyzed. In some cases, single dendrites were postsynaptic to both dynorphin and TH‐immunoreactive terminals. We conclude that dynorphin‐immunoreactive terminals potently modulate, and most likely inhibit, target neurons in both subregions of the rat nucleus accumbens. This modulatory action could attenuate or potentiate incoming catecholamine signals on more distal dendrites of the accumbens neurons. The findings also suggest potential sites for presynaptic modulatory interactions involving dynorphin and catecholamine or other tra

ISSN:0092-7317    

DOI:10.1002/cne.903410102

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

年代:1994

数据来源: WILEY

摘要:

AbstractSpiny stellate neurons of area 17 of the cat's visual cortex were physiologically characterised and injected intracellularly with horseradish peroxidase. Six neurons from sublamina 4A were selected. Five had the S‐type of simple receptive fields; one had a complex receptive field. Their axons formed boutons mainly in layers 3 and 4. An electron microscopic examination of 45 boutons showed that each bouton formed one asymmetric synapse on average. Spines were the most frequent synaptic target (74%); dendritic shafts formed the remainder (26%). On the basis of ultrastructural characteristics, 8% of the target dendrites were characterised as originating from smooth γ‐aminobutyrate‐ergic (GABAergic) neurons. Thus the major output of spiny stellate neurons is to other spiny neurons, probably pyramidal neurons in layer 3 and spiny stellates in l

ISSN:0092-7317    

DOI:10.1002/cne.903410103

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe synaptic input of six spiny stellate neurons in sublamina 4A of cat area 17 was assessed by electron microscopy. The neurons were physiologically characterized and filled with horseradish peroxidase in vivo. After processing the neurons were reconstructed at the light microscopic level using computer‐assisted methods and analyzed quantitatively. The extensive branching of the dendritic tree about 50 μm from the soma meant that the distal branches constituted five times the length of proximal dendrite. Proximal and distal portions of a single dendrite from each neuron were examined in series of ultrathin sections (1,456 sections) in the electron microscope. The majority (79%) of the 263 synapses examined were asymmetric; the remainder (21%) were symmetric. Symmetric synapses formed 35% of synapses sampled on proximal dendrites and were usually located on the shaft. They formed only 4% of synapses sampled on distal dendrites. Spines accounted for less than half of the total asymmetric synapses (45%); the remainder were on shafts. Symmetric synapses formed with four of 92 spines. Nine spines formed no synapses. Spiny stellate neurons in cat visual cortex appear to differ considerably from pyramidal neurons in having a significant asymmetric (excitatory) synaptic input to the dendritic sha

ISSN:0092-7317    

DOI:10.1002/cne.903410104

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

年代:1994

数据来源: WILEY

摘要:

AbstractOur hypothesis was that spiny stellate neurons in layer 4 of cat visual cortex receive polyneuronal innervation. We characterised the synapses of four likely sources of innervation by three simple criteria: the type of synapse, the target (spine, dendritic shaft), and the area of the presynaptic bouton. The layer 6 pyramids had the smallest boutons and formed asymmetric synapses mainly with the dendritic shaft. The thalamic afferents had the largest boutons and formed asymmetric synapses mainly with spines. The spiny stellates had medium‐sized boutons and formed asymmetric synapses mainly with spines. We used these to make a “template” to match against the boutons forming synapses with the spiny stellate dendrite. Of the asymmetric synapses, 45% could have come from layer 6 pyramidal neurons, 28% from spiny stellate neurons, and 6% from thalamic afferents. The remaining 21% of asymmetric synapses could not be accounted for without assuming some additional selectivity of the presynaptic axons. Additional asymmetric synapses may come from a variety of sources, including other cortical neurons and subcortical nuclei such as the claustrum. Of the symmetric synapses, 84% could have been provided by clutch cells, which form large boutons. The remainder, formed by small boutons, probably come from other smooth neurons in layer 4, e.g., neurogliaform and bitufted neurons. Our analysis supports the hypothesis that the spiny stellate receives polyneuronal innervation, perhaps from all the sources of boutons in layer 4. Although layer 4 is the major recipient of thalamic afferents, our results show that they form only a few percent of the synapses of layer 4 spiny stellate ne

ISSN:0092-7317    

DOI:10.1002/cne.903410105

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

年代:1994

数据来源: WILEY

摘要:

AbstractBirds respond to hair cell loss by stimulating cell division in the otherwise mitotically quiescent sensory epithelium and by generating new hair cells. We examined cell proliferation during hair cell regeneration in chick basilar papilla by using 5‐bromo‐2′ ‐deoxyuridine (BrdU). Chicks were noise exposed for 4 or 24 hours and injected with BrdU, and cochleae were immunohistochemically labeled to detect BrdU. Immunoreactivity after short‐term postinjection survival identified when cells entered S phase. For both 4 and 24 hour exposures, cells in S phase were first detected in the sensory epithelium after an injection at 18 hours after the onset of exposure and were also present after injections at 24, 30, 36, 42, 48, 72, 96, 120, and 144 hours. The most cells in S (or G2) phase were detected at 42 and 72 hours for 24 hour exposures and at 48 hours for 4 hour exposures. Chicks that survived for long periods after injection had BrdU‐labeled hair cells indicating that precursor cells that divided in the presence of BrdU generated new hair cells. Moreover, labeled hair cells and supporting cells were grouped into discrete clusters, suggesting that cells within each cluster are clonally related. Support for this hypothesis was provided by experiments showing that the number of labeled cells increased when chicks survived for longer periods after a single BrdU injection. These findings suggest that progenitors within the sensory epithelium may undergo several rounds of division to generate the appropriate number of new hair cells and suppo

ISSN:0092-7317    

DOI:10.1002/cne.903410106

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe distribution pattern of immunoreactive β‐endorphin neurons was studied in female guinea pigs that were ovariectomized, and one week later were injected with 25 μg estradiol benzoate or oil. The animals (5 from each group) were perfused after 24 hours with 4% paraformaldehyde. The locations of β‐endorphin cells and fibers were determined using avidin‐biotin immunohistochemistry on free‐floating vibratome sections. β‐endorphin‐immunoreactive fibers were distributed widely throughout specific regions of the rostral forebrain, similar to what has been described in other species. β‐endorphin cell bodies were found in the arcuate nucleus and in adjacent ventrolateral areas throughout the rostrocaudal extent of the basal hypothalamus. Cells immunoreactive to β‐endorphin were also present in the caudal part of the ventromedial nucleus of the hypothalamus. The number of β‐endorphin neurons was quantified in anatomically matched sections through the rostral, medial and caudal basal hypothalamus of estradiol benzoate‐ and oil‐treated guinea pigs. Analysis of variance revealed that the number of immunoreactive β‐endorphin cells was significantly increased in all regions of the basal hypothalamus of estrogen‐treated guinea pigs as compared to vehicle‐treated animals (P<0.01). These data indicate that in the guinea pig, the number of neurons expressing β‐endorphin is increased in the arcuate nuc

ISSN:0092-7317    

DOI:10.1002/cne.903410107

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

年代:1994

数据来源: WILEY

摘要:

AbstractThe morphology of cortical neurons grafted into (or near) the rat striatum was studied by means of intracellular Lucifer yellow injections in fixed slices. Rat donor syngeneic cortical tissue (from postnatal day 1 old rats; AO strain) as well as mouse donor xenogeneic cortical tissue (prenatal day 19; C3H/HE strain) were grafted as solid pieces into 8–12 week‐old rats (AO strain). Recipients of mouse xenografts were immunosuppressed with a monoclonal antibody against the interleukin‐2 receptor. After perfusion and sectioning of the graft‐containing areas, individual slices were incubated in the DNA stain 4.6‐diamidino‐2‐phenylindole (DAPI) to visualize the cell nuclei. Grafts could be easily identified by a surrounding rim of astrocytes which outline the border between grafted and host tissue. Grafted cortical neurons were intracellularly filled with Lucifer yellow, DAB‐photoconverted, and further processed for light and electron microscopy.In general, no cortical lamination could be observed in the grafted rat and mouse cortical tissue, but neurons were loosely packed throughout the graft. Two major cell types could be identified in all grafts investigated so far. The majority resembled those described as spiny neurons (85%), which could be further classified into pyramid‐like, spiny stellate‐like or fusiform spiny neurons, with somata ranging between 15 and 25 μm in diameter. The remaining 15% resembled non‐spiny neurons with either a multipolar basket‐like or fusiform morphology. Dendrites of spiny and non‐spiny neurons, which could extend to distances up to 400 μm, were never seen to cross the astrocytic border, but some main axon and axonal collaterals of spiny neurons were found to leave the graft. On the basis of light microscopic observations no difference was found between mouse and rat grafted cortical neurons. The results of this study show that grafted cortical neurons retain some of the characteristic features of neurons in the intact adult cerebral cortex, although there appears to be a greater preponderance of spiny neurons in grafted tissue. This may reflect an immaturity of the grafted tissue or a response

ISSN:0092-7317    

DOI:10.1002/cne.903410108

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

年代:1994

数据来源: WILEY

摘要:

AbstractIn the cerebral cortex, local circuit neurons provide critical inhibitory control over the activity of pyramidal neurons, the major class of excitatory efferent cortical cells. The calciumbinding proteins, calretinin, calbindin, and parvalbumin, are expressed in a variety of cortical local circuit neurons. However, in the primate prefrontal cortex, relatively little is known, especially with regard to calretinin, about the specific classes or distribution of local circuit neurons that contain these calcium‐binding proteins. In this study, we used immunohistochemical techniques to characterize and compare the morphological features and distribution in macaque monkey prefrontal cortex of local circuit neurons that contain each of these calcium‐binding proteins.On the basis of the axonal features of the labeled neurons, and correlations with previous Golgi studies, calretinin appeared to be present in double‐bouquet neurons, calbindin in neurogliaform neurons and Martinotti cells, and parvalbumin in chandelier and wide arbor (basket) neurons. Calretinin was also found in other cell populations, such as a distinctive group of large neurons in the infragranular layers, but it was not possible to assign these neurons to a known cell class. In addition, although the animals studied were adults, immunoreactivity for both calretinin and calbindin was found in Cajal‐Retzius neurons of layer I. Dual labeling studies confirmed that with the exception of the Cajal‐Retzius neurons, each calcium‐binding protein was expressed in separate populations of prefrontal cortical neurons.Comparisons of the laminar distributions of the labeled neurons also indicated that these calcium‐binding proteins were segregated into discrete neuronal populations. Calretinin‐positive neurons were present in greatest density in deep layer I and layer II, calbindin‐immuno‐reactive cells were most dense in layers II‐superficial III, and parvalbumin‐containing neurons were present in greatest density in the middle cortical layers. In addition, the relative density of calretinin‐labeled neurons was approximately twice that of the calbindin‐ and parvalbumin‐positive neurons. However, within each group of labeled neurons, their laminar distribution and relative density did not differ substantially across regions of the prefrontal cortex.These findings demonstrate that calretinin, calbindin, and parvalbumin are markers of separate populations of local circuit neurons in monkey prefrontal cortex, and that they may be useful tools in unraveling the intrinsic inhibitory circuitry of the primate prefrontal cortex in b

ISSN:0092-7317    

DOI:10.1002/cne.903410109

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

年代:1994

数据来源: WILEY

摘要:

AbstractUsing choline acetyltransferase (ChAT) immunocytochemistry and acetylcholinesterase (AChE) histochemistry, we investigated regional and laminar differences in cholinergic innervation in the cerebral cortex, hippocampus, amygdala, and thalamus of mice. In mice, unlike rats, the patterns of ChAT‐immunostained and AChE‐positive fibers are virtually identical in the cortex and are organized in a trilaminar pattern with cholinergic processes prominent in layers I and IV and within the lower portion of layer V and upper segment of layer VI. ChAT‐immunoreactive cells were not seen in cortex. In the amygdala, the basolateral nucleus showed the highest density of cholinergic processes. In the hippocampus, a thin, dense band of ChAT‐labeled processes was present in the inner segment of the molecular layer of the dentate gyrus and within the stratum oriens of CA1‐3, adjacent to the basal aspect of pyramidal cells. Within the thalamus, anteroventral, mediodorsal (lateral portion), intralaminar, and reticular nuclei showed high densities of cholinergic processes. The results of this study provide the basis for examining the effects of transgenes and age on forebrain cholinergi

ISSN:0092-7317    

DOI:10.1002/cne.903410110

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

年代:1994

数据来源: WILEY

摘要:

AbstractFive pairs of identified 5HT‐IR cells in the deutocerebrum of the crayfishCheraxare known to have their synaptic endings in the accessory and olfactory lobes. Two of these cells, one on each side of the brain, are significantly larger than the others. Dye fills of these “giant” cells reveal each to be an interneuron with its branches confined to, but distributed throughout, the olfactory and accessory lobes on the side of the brain ipsilateral to its cell body and with no branches to the contralateral side. Intracellular recordings from the giant cells were made while stimulating the olfactory afferents and tracts within the brain in an attempt to discover the inputs and outputs to the cells. Electrical stimulation of chemoreceptor sensilla on the outer branch of the antennule does not excite the giant 5HT neurons. Focal extracellular electrical stimulation of the olfactory globular tract containing the axons of projection neurons from the olfactory and accessory lobes produces excitatory synaptic potentials and action potentials in the giant cells. Focal extracellular electrical stimulation of the deutocerebral commissure, the axons of which terminate in the glomeruli of the accessory lobes, also results in excitation of the giant cells. We conclude that the input to the giant cells is via axons in the deutocerebral commissure and collaterals from the projection neurons, ending in the glomeruli of the accessory lobes. The output of the giant cells is to the olfactory lobes, where it may serve to modulate olfactory si

ISSN:0092-7317    

DOI:10.1002/cne.903410111

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

年代:1994

数据来源: WILEY