bluuebunny/crossref_metadata_2025_split huggingface dataset:
GABAergic regulation of noradrenergic spinal projection neurons of the A5 cell group in the rat: An electron microscopic analysis
Authors: Kwiat Geoffrey C. , Liu Hantao , Williamson Andrew M. , Basbaum Allan I. 
Published: January 2005

AbstractRecent studies have demonstrated an important contribution of the A5 noradrenergic cell group of the rostral medulla in the regulation of nociceptive messages at the level of the spinal cord. These noradrenergic controls parallel those arising from the serotonin‐containing neurons of the nucleus raphe magnus. In the present study, we used postembedding immunogold staining to identify GABA‐immunoreactive terminals that synapse upon identified spinally projecting noradrenergic neurons of the A5 cell group in the rat. A5 projection neurons were identified by Fluoro‐Gold transport from the spinal cord; sections containing retrogradely labelled cells were then immunoreacted for tyrosine hydroxylase (TH) to identify the catecholamine‐containing, presumed noradrenergic, neurons. Double‐labelled A5 cells were intracellularly filled with Lucifer Yellow (LY) and then the LY was photo‐oxidized to an electron‐dense product.Seven intracellularly filled TH‐immunoreactive projection neurons were studied with postembedding immunocytochemistry. Each A5 neuron received a significant GABA‐immunoreactive terminal input. Out of a pooled total of 151 terminal profiles found in apposition to intracellularly labelled somatic and dendritic profiles, 31 (20.5%) were GABA‐immunoreactive. The proportion of GABA‐immunoreactive terminals that contacted somatic profiles (12/72; 17%) was similar to the proportion that contacted TH‐labelled dendritic profiles (19/79; 24%). There was a discernible synaptic specialization in about 50% of the labelled terminals that contacted the TH projection neuron. Both symmetric and asymmetric synaptic specializations were found. Labelled terminals contained round or pleimorphic vesicles, but not flat vesicles; many also contained dense‐core vesicles.Our results indicate that noradrenergic neurons of the A5 cell group, which contribute to both antinociceptive and cardiovascular controls through their projection to the spinal cord, are regulated by local GABAergic, presumably inhibitory, mechanisms. Whether the initiation of A5 neuron activity results from a lifting of tonic GABAergic inhibitory control, as has been proposed for the neurons of the nucleus raphe magnus, remains to be determined.
Hair cell regeneration after streptomycin toxicity in the avian vestibular epithelium
Authors: Weisleder Pedro , Rubel Edwin W 
Published: January 2005

AbstractRecent reports documented the ability of the posthatch avian vestibular epithelia to produce hair cells continually at a low rate. This project was designed to investigate whether, in addition, the chicken vestibular system is capable of regenerating its sensory epithelium in response to a lesion. Aminoglycoside injections were given to young birds in order to damage the vestibular epithelium. Tritiated thymidine injections were used to label cells produced in response to the lesion. Treatment and age‐matched control animals were killed at 1 day, 20 days, or 60 days after aminoglycoside injections, and vestibular organs were processed for autoradiography. Our results show that the chicken vestibular sensory epithelium is capable of regenerating hair cells after severe damage. Moreover, the epithelium is capable of complete anatomical recovery. Finally, drug damage increases the pace at which hair cells are replaced, compared to the rate of hair cell turnover in untreated tissue. © 1993 Wiley‐Liss, Inc.
Lesion‐induced changes in the central terminal distribution of galanin‐immunoreactive axons in the dorsal column nuclei
Authors: Hoeflinger Brian F. , Bennett‐Clarke Carol A. , Chiaia Nicolas L. , Killackey Herbert P. , Wall John T. , Rhoades Robert W. 
Published: January 2005

AbstractRats that sustained forelimb removal on either embryonic day (E) 16, on the day of birth (P‐0), or transection of the brachial plexus in adulthood had brainstem sections stained for galanin, calcitonin gene‐related peptide (CGRP), or substance P (SP) at various intervals after these lesions were made. In normal adult rats, only a few galanin‐immunoreactive fibers are present in the cuneate nucleus and most are located in its caudal portion. CGRP‐positive axons are also sparse in the cuneate and are distributed mainly in the periphery of the nucleus. SP‐positive axons are seen throughout the cuneate nucleus. In rats that sustained forelimb removals at birth or transection of the brachial plexus in adulthood, dense galanin immunoreactivity was present throughout the cuneate nucleus at all rostrocaudal levels on the side of the brainstem ipsilateral to the lesion. The changes after lesions that were made in the adult animals were apparent within 1 week, the earliest time analyzed. Increases in galanin immunoreactivity in the cuneate of animals that sustained forelimb removals on P‐0 were first visible on P‐2. Neither forelimb removal at birth nor brachial plexus lesions in adulthood had any qualitative effect upon the distribution or density of CGRP‐ or SP‐immunoreactivity in the cuneate nucleus.Removal of a forelimb on E‐16 did not increase the density of galanin‐immunoreactive fibers in the cuneate nucleus. Such lesions also failed to produce any appreciable change in the density of either CGRP‐ or SP‐positive fibers in the cuneate nucleus. The present data raise the possibility that large caliber, non‐peptidergic primary afferent axons which innervate the cuneate nucleus may express galanin after damage at birth or in adulthood. © 1993 Wiley‐Liss, Inc.
Developmental plasticity in cerebellar tactile maps: Fractured maps retain a fractured organization
Authors: Gonzalez Leila , Shumway Caroly , Morissette Josée , Bower James M. 
Published: January 2005

AbstractPlasticity following deafferentation has been repeatedly demonstrated in topographic sensory maps in the mammalian brain. In this paper we investigated the developmental plasticity of the fractured somatotopic map found in the tactile regions of the rat cerebellum. At various stages of postnatal development between postnatal days 1 and 30, we cauterized the infraorbital branch of the trigeminal nerve, which innervates the upper lip, furry buccal pad, and vibrissae that are represented within cerebellar folium crus IIa. The organization of the crus IIa map was then examined 2 to 3 months after denervation. We found that tactile receptive fields had reorganized throughout the denervated area but maintained a fractured somatotopy. Comparison of the reorganization in different animals showed that the denervated upper lip region was consistently and predominantly replaced by representation of the upper incisors. Analysis of evoked field potentials revealed an alteration, in denervated animals, of the response of the granule cell layer to brief tactile stimulation. This response in normal animals consists of two components at different latencies. Animals lesioned later in development were less likely to have the short latency component. This result suggests a difference in the developmental sensitivity of different cerebellum‐related pathways to nerve lesions.
Cochlear cytogenesis visualized through pulse labeling of chick embryos in culture
Authors: Katayama Akiko , Corwin Jeffrey T. 
Published: January 2005

AbstractCytogenesis in the basilar papilla sensory epithelium of the chicken was investigated through pulse labeling of proliferative cells. Tritiated‐thymidine was injected intravenously in chick embryos cultured in petri dishes. All embryos received the injection on the seventh day of incubation (E7), when the progenitors of hair cells and supporting cells are replicating deoxyribonucleic acid (DNA). Cells that were in the synthesis phase of the cell cycle, either at the time of the 3H‐thymidine pulse or within 2 hours, incorporated detectable levels of the radioactive DNA precursor. Labeled cells were identified in cochleae from embryos fixed at 0.5, 1, 2, 4, 6, 12 hours, 6 and 8 days after the pulse. One hour after the injection the majority of labeled nuclei were in the basal and middle strate of the sensory epithelium. Four to 6 hours after the injection, a greater number of labeled cells appeared in the lumenal stratum. The patterns of labeled cells in embryos fixed immediately after the injection of 3H‐thymidine and in others fixed 6 to 8 days after the injection were unchanged, suggesting that the progenitor cells divide and their progeny differentiate in the sensory epithelium without appreciable transverse migration. Mitotic figures were usually observed only in the lumenal stratum. Analysis of DNA content in the population of Feulgen‐stained nuclei at three levels of depth through the epithelium also produced results consistent with the conclusion that vertical nuclear migration occurs during development of the cells in this sensory epithelium. © 1993 Wiley‐Liss, Inc.
NGF can induce a ‘young’ pattern of reinnervation in transplanted cerebral blood vessels from ageing rats
Authors: Gavazzi Isabella , Cowen Timothy 
Published: January 2005

AbstractPeripheral target tissues can determine age‐related changes in their density and pattern of innervation. We have shown previously that middle cerebral arteries from young and old rats transplanted in oculo in young hosts become reinnervated with a density and pattern of innervation that is typical of the age of the donor, i.e., the density of reinnervation on old transplants is 50% lower than on young transplants. The alterations in the target tissues responsible for their decreased innervation in old age are still unknown. We have investigated the possibility that increasing the availability of nerve growth factor (NGF) might restore the pattern and density of perivascular nerves on old blood vessels to levels of innervation typical of young tissues. Old middle cerebral transplants were therefore treated with NGF or vehicle by three weekly transcleral injections. NGF treatment markedly increased the reinnervation of old transplants, restoring the density and pattern of innervation to one characteristic of young animals. NGF produced an equivalent increase in nerve growth on young and old transplants, thus confirming that the receptivity of old blood vessels to reinnervation is not impaired. Control experiments were performed by treating transplants with saline, bovine serum albumin, or cytochrome c. Unexpectedly, bovine serum albumin was shown to promote axonal growth, although to a lesser extent and with a different pattern than NGF. © 1993 Wiley‐Liss, Inc.
Topographic organization of rat locus coeruleus and dorsal raphe nuclei: Distribution of cells projecting to visual system structures
Authors: Waterhouse Barry D. , Border Barbara , Wahl Linda , Mihailoff Gregory A. 
Published: January 2005

AbstractPrevious reports from this laboratory and elsewhere have provided evidence that the locus coeruleus (LC) and dorsal raphe (DR) nuclei are topographically organized with respect to their efferent targets. Whereas most of these previous studies have focused on relationships between these monoamine‐containing brainstem nuclei and cerebral cortex, basal ganglia, and limbic structures, they have not systematically examined the distribution of LC and DR cells that project to multiple structures with common sensory or motor functions. The goal of the present study was to characterize and compare the distributions of LC and DR cells which project to different visual areas of the rat central nervous system. Long‐Evans hooded rats received unilateral pressure injections of the retrograde tracer wheat germ agglutinin‐horseradish peroxidase in either the dorsal lateral geniculate, ventral lateral geniculate, or lateral posterior nucleus of thalamus; superior colliculus, cortical area 17, cortical area 18a/b cerebellar vermis (lobules VI and VII); or paraflocculus. Transverse sections through the midbrain and pons were examined by light microscopy after performing routine tetramethyl benzidine histochemical procedures. For all cases studied, retrogradely labeled cells were observed throughout the rostrocaudal extent of the LC and DR; however, labeling patterns which were distinctive for different injection sites were noted in each of these brainstem nuclei. The major conclusion drawn from this work is that subsets of LC and DR cells which project to different target structures within the rat visual system are found in overlapping but not necessarily coextensive zones within these nuclei. These studies provide further evidence of a rough topographic ordering within both the LC and DR nuclei, as well as support a new hypothesis that the outputs from each of these nuclei are organized with respect to the sensory related functions of their efferent targets. © 1993 Wiley‐Liss, Inc.
Diencephalic gustatory connections in the channel catfish
Authors: Lamb Charles F. , Caprio John 
Published: January 2005

AbstractVertebrate gustatory systems include a tertiary ascending pathway from a secondary gustatory nucleus in the hindbrain to several forebrain nuclei. This connection is prominent in catfish, corresponding to their highly developed sense of taste. Iontophoretic injections of horseradish peroxidase were used to identify the specific target nuclei of the tertiary gustatory pathway in channel catfish and to characterize those nuclei by their respective connections.Efferents from the secondary gustatory nucleus (nGS) ascend in the tertiary gustatory tract to the caudal inferior lobe, where they terminate caudally in the nucleus lobobulbaris (nLB) and nucleus centralis (nCLI), and rostrally in the nucleus diffusus (nDLI). Secondary projections from the facial lobe (FL) also terminate in the nLB and in the nucleus subglomerulus (nSG). The nLB forms three cell groups (caudal‐nLB, rostrolateral‐rl nLB, parvicellular‐nLBp), which project to the facial lobe, vagal lobe, and telencephalon, respectively. Cells from the nCLI project throughout the caudal inferior lobe and to the acousticolateral torus semicircularis and telencephalon, while the nDLI and nSG have intrinsic connections within the inferior lobe. The lateral thalamic nucleus projects from this region back to the nGS.Through these identified connections several mechanisms for the processing of gustatory information can be proposed. The descending projections from the nLB and nLT could provide feedback to the primary and secondary gustatory nuclei, and could modulate feeding‐related motor circuits in the medulla. The connections of nCLI and nLBp with the telencephalon allow for the involvement of gustation in learning processes and other complex behaviors. © 1993 Wiley‐Liss, Inc.
Dendritic domains of medium spiny neurons in the primate striatum: Relationships to striosomal borders
Authors: Walker Ruth H. , Arbuthnott Gordon W. , Baughman Robert W. , Graybiel Ann M. 
Published: January 2005

AbstractMedium spiny neurons are the projection neurons of the striatum. They receive the majority of striatal afferents, and they make up the vast majority of all neurons in the striatum. These densely spiny cells thus constitute a major substrate for input‐output processing in the striatum. In the experiments described here we analyzed the dendritic fields of spiny neurons in the squirrel monkey striatum and plotted their orientations with respect to the borders between striosomes and matrix. Medium‐sized spiny neurons in the caudate nucleus were filled intracellularly in a fixed‐slice preparation with the fluorescent dye Lucifer Yellow. Dendritic arbors were reconstructed following immunostaining of the injected neurons with antiserum to Lucifer Yellow and counterstaining for striosome/matrix compartments. A majority of the medium spiny neurons studied had dendritic arborizations that remained within their compartment of origin. Thus the striosome/matrix subdivision not only partitions neurotransmitter molecules and extrinsic striatal connections into two domains in the primate caudate nucleus, but also constrains the dendritic arbors of many projection neurons there. Other medium spiny neurons, however, in both striosomes and matrix, had dendrites that crossed from one compartment into the other. About a quarter of the spiny neurons reconstructed had at least one such crossing dendrite. These results suggest that compartmentalization of afferent and efferent processing by projection neurons in the primate striatum is not absolute. For a subpopulation of spiny neurons in striosomes and matrix, inputs to one compartment could have a direct influence on output cells of the other. © 1993 Wiley‐Liss,Inc.
Morphology of astrocytes and oligodendrocytes during development in the intact rat optic nerve
Authors: Butt Arthur M. , Ransom Bruce R. 
Published: January 2005

AbstractThe detailed three‐dimensional morphology of macroglial cells was determined throughout postnatal development in the intact rat optic nerve, a central nervous system white matter tract. Over 750 cells were analyzed by intracellular injection of horseradish peroxidase or Lucifer Yellow to provide a new perspective of glial differentiation in situ. Retrograde analysis of changes in glial morphology allowed us to identify developmental timetables for three morphological subclasses of astrocytes and oligodendrocytes, and to estimate their time of emergence from undifferentiated glial progenitors. Glial progenitors were recognised throughout postnatal development and persisted in 35‐day‐old nerves, where we suggest they represent adult progenitor cells. Astrocytes were present at birth, but the majority of these cells developed over the first week as three morphological classes emerged having either transverse, random, or longitudinal process orientation. Several lines of evidence led us to believe that the majority of astrocytes in the rat optic nerve were morphological variations of a single cell type. Young oligodendrocytes were first observed 2 days after birth, indicating that they diverged from progenitors at or near this time. During early development these cells extended a large number of fine processes, which then bifurcated and extended along axons. Later, as myelination proceeded, oligodendrocytes exhibited fewer processes which grew symmetrically and uniformly along the axons, resulting in a highly stereotypic mature oligodendrocyte form. Our analysis of oligodendrocyte growth suggests that these cells did not myelinate axons in a random manner and that axons may influence the myelinating processes of nearby oligodendrocytes. © 1993 Wiley‐Liss, Inc.
Dynorphin‐immunoreactive terminals in the rat nucleus accumbens: Cellular sites for modulation of target neurons and interactions with catecholamine afferents
Authors: van Bockstaele Elisabeth J. , Sesack Susan R. , Pickel Virginia M. 
Published: January 2005

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 transmitters in apposed terminals.
Synaptic output of physiologically identified spiny stellate neurons in cat visual cortex
Authors: Anderson John C. , Douglas Rodney J. , Martin Kevan A. C. , Nelson J. Charmaine 
Published: January 2005

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 layer 4.
Identification of the timing of S phase and the patterns of cell proliferation during hair cell regeneration in the chick cochlea
Authors: Stone Jennifer S. , Cotanche Douglas A. 
Published: January 2005

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 supporting cells.