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Cell Dendrites (cell + dendrite)
Kinds of Cell Dendrites Selected AbstractsOlfactory epithelium influences the orientation of mitral cell dendrites during developmentDEVELOPMENTAL DYNAMICS, Issue 2 2005Laura López-Mascaraque Abstract We have established previously that, although the olfactory epithelium is absent in the homozygous Pax-6 mutant mouse, an olfactory bulb-like structure (OBLS) does develop. Moreover, this OBLS contains cells that correspond to mitral cells, the primary projection neurons in the olfactory bulb. The current study aimed to address whether the dendrites of mitral cells in the olfactory bulb or in the OBLS mitral-like cells, exhibit a change in orientation in the presence of the olfactory epithelium. The underlying hypothesis is that the olfactory epithelium imparts a trophic signal on mitral and mitral-like cell that influences the growth of their primary dendrites, orientating them toward the surface of the olfactory bulb. Hence, we cultured hemibrains from wild-type and Pax 6 mutant mice from two different embryonic stages (embryonic days 14 and 15) either alone or in coculture with normal olfactory epithelial explants or control tissue (cerebellum). Our results indicate that the final dendritic orientation of mitral and mitral-like cells is directly influenced both by age and indeed by the presence of the olfactory epithelium. Developmental Dynamics 232:325,335, 2005. © 2004 Wiley-Liss, Inc. [source] Convergence of multisensory inputs in Xenopus tadpole tectumDEVELOPMENTAL NEUROBIOLOGY, Issue 14 2009Masaki Hiramoto Abstract The integration of multisensory information takes place in the optic tectum where visual and auditory/mechanosensory inputs converge and regulate motor outputs. The circuits that integrate multisensory information are poorly understood. In an effort to identify the basic components of a multisensory integrative circuit, we determined the projections of the mechanosensory input from the periphery to the optic tectum and compared their distribution to the retinotectal inputs in Xenopus laevis tadpoles using dye-labeling methods. The peripheral ganglia of the lateral line system project to the ipsilateral hindbrain and the axons representing mechanosensory inputs along the anterior/posterior body axis are mapped along the ventrodorsal axis in the axon tract in the dorsal column of the hindbrain. Hindbrain neurons project axons to the contralateral optic tectum. The neurons from anterior and posterior hindbrain regions project axons to the dorsal and ventral tectum, respectively. While the retinotectal axons project to a superficial lamina in the tectal neuropil, the hindbrain axons project to a deep neuropil layer. Calcium imaging showed that multimodal inputs converge on tectal neurons. The layer-specific projections of the hindbrain and retinal axons suggest a functional segregation of sensory inputs to proximal and distal tectal cell dendrites, respectively. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Death and survival of heterozygous Lurcher Purkinje cells In vitroDEVELOPMENTAL NEUROBIOLOGY, Issue 8 2009Hadi S. Zanjani Abstract The differentiation and survival of heterozygous Lurcher (+/Lc) Purkinje cells in vitro was examined as a model system for studying how chronic ionic stress affects neuronal differentiation and survival. The Lurcher mutation in the ,2 glutamate receptor (GluR,2) converts an orphan receptor into a membrane channel that constitutively passes an inward cation current. In the GluR,2+/Lc mutant, Purkinje cell dendritic differentiation is disrupted and the cells degenerate following the first week of postnatal development. To determine if the GluR,2+/Lc Purkinje cell phenotype is recapitulated in vitro, +/+, and +/Lc Purkinje cells from postnatal Day 0 pups were grown in either isolated cell or cerebellar slice cultures. GluR,2+/+ and GluR,2+/Lc Purkinje cells appeared to develop normally through the first 7 days in vitro (DIV), but by 11 DIV GluR,2+/Lc Purkinje cells exhibited a significantly higher cation leak current. By 14 DIV, GluR,2+/Lc Purkinje cell dendrites were stunted and the number of surviving GluR,2+/Lc Purkinje cells was reduced by 75% compared to controls. However, treatment of +/Lc cerebellar cultures with 1-naphthyl acetyl spermine increased +/Lc Purkinje cell survival to wild type levels. These results support the conclusion that the Lurcher mutation in GluR,2 induces cell autonomous defects in differentiation and survival. The establishment of a tissue culture system for studying cell injury and death mechanisms in a relatively simple system like GluR,2+/Lc Purkinje cells will provide a valuable model for studying how the induction of a chronic inward cation current in a single cell type affects neuronal differentiation and survival. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] A novel role for MNTB neuron dendrites in regulating action potential amplitude and cell excitability during repetitive firingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2008Richardson N. Leão Abstract Principal cells of the medial nucleus of the trapezoid body (MNTB) are simple round neurons that receive a large excitatory synapse (the calyx of Held) and many small inhibitory synapses on the soma. Strangely, these neurons also possess one or two short tufted dendrites, whose function is unknown. Here we assess the role of these MNTB cell dendrites using patch-clamp recordings, imaging and immunohistochemistry techniques. Using outside-out patches and immunohistochemistry, we demonstrate the presence of dendritic Na+ channels. Current-clamp recordings show that tetrodotoxin applied onto dendrites impairs action potential (AP) firing. Using Na+ imaging, we show that the dendrite may serve to maintain AP amplitudes during high-frequency firing, as Na+ clearance in dendritic compartments is faster than axonal compartments. Prolonged high-frequency firing can diminish Na+ gradients in the axon while the dendritic gradient remains closer to resting conditions; therefore, the dendrite can provide additional inward current during prolonged firing. Using electron microscopy, we demonstrate that there are small excitatory synaptic boutons on dendrites. Multi-compartment MNTB cell simulations show that, with an active dendrite, dendritic excitatory postsynaptic currents (EPSCs) elicit delayed APs compared with calyceal EPSCs. Together with high- and low-threshold voltage-gated K+ currents, we suggest that the function of the MNTB dendrite is to improve high-fidelity firing, and our modelling results indicate that an active dendrite could contribute to a ,dual' firing mode for MNTB cells (an instantaneous response to calyceal inputs and a delayed response to non-calyceal dendritic excitatory postsynaptic potentials). [source] Characterization of a transneuronal cytokine family Cbln , regulation of secretion by heteromeric assemblyEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2007Takatoshi Iijima Abstract Cbln1, a member of the C1q and tumor necrosis factor superfamily, plays crucial roles as a cerebellar granule cell-derived transneuronal regulator of synapse integrity and plasticity in Purkinje cells. Although other Cbln family members, Cbln2,Cbln4, have distinct spatial and temporal patterns of expression throughout the CNS, their biochemical and biological properties have remained largely uncharacterized. Here, we demonstrated that in mammalian heterologous cells, Cbln2 and Cbln4 were secreted as N-linked glycoproteins, like Cbln1. In contrast, despite the presence of a functional signal sequence, Cbln3 was not secreted when expressed alone but was retained in the endoplasmic reticulum (ER) or cis -Golgi because of its N-terminal domain. All members of the Cbln family formed not only homomeric but also heteromeric complexes with each other in vitro. Accordingly, when Cbln1 and Cbln3 were co-expressed in heterologous cells, a proportion of the Cbln1 proteins was retained in the ER or cis -Golgi; conversely, some Cbln3 proteins were secreted together with Cbln1. Similarly, in wild-type granule cells expressing Cbln1 and Cbln3, Cbln3 proteins were partially secreted and reached postsynaptic sites on Purkinje cell dendrites, while Cbln3 was almost completely degraded in cbln1 -null granule cells. These results indicate that like Cbln1, Cbln2 and Cbln4 may also serve as transneuronal regulators of synaptic functions in various brain regions. Furthermore, heteromer formation between Cbln1 and Cbln3 in cerebellar granule cells may modulate each other's trafficking and signaling pathways; similarly, heteromerization of other Cbln family proteins may also have biological significance in other neurons. [source] Activation of class I metabotropic glutamate receptors limits dendritic growth of Purkinje cells in organotypic slice culturesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006Alexandra Sirzen-Zelenskaya Abstract The development of the dendritic tree of a neuron is a complex process which is thought to be regulated strongly by signals from afferent fibers. We showed previously that the blockade of glutamatergic excitatory neurotransmission has little effect on Purkinje cell dendritic development. We have now studied the effects of glutamate receptor agonists on the development of Purkinje cell dendrites in mouse organotypic slice cultures. The activation of N -methyl- d -aspartate receptors had no major effect on Purkinje cell dendrites and the activation of (RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid receptors was strongly excitotoxic so that no analysis of its effects on dendritic development was possible. The activation of metabotropic glutamate receptors led to a very strong inhibition of dendritic growth, resulting in Purkinje cells with very small stubby dendrites. This effect was specific for the activation of class I metabotropic glutamate receptors and could not be reduced by blocking synaptic transmission in the cultures, indicating that it was mediated by receptors present on Purkinje cells. Pharmacological experiments suggest that the signaling pathway involved does not require activation of phospholipase C or protein kinase C. The inhibition of dendritic growth by activation of class I metabotropic glutamate receptor could be a useful negative feedback mechanism for limiting the size of the dendritic tree of Purkinje cells after the establishment of a sufficient number of parallel fiber contacts. This developmental mechanism could protect Purkinje cells from excitotoxic death through excessive release of glutamate from an overload of parallel fiber contacts. [source] Dynamics of Ca2+ and Na+ in the dendrites of mouse cerebellar Purkinje cells evoked by parallel fibre stimulationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2003Akinori Kuruma Abstract Ca2+ and Na+ play important roles in neurons, such as in synaptic plasticity. Their concentrations in neurons change dynamically in response to synaptic inputs, but their kinetics have not been compared directly. Here, we show the mechanisms and dynamics of Ca2+ and Na+ transients by simultaneous monitoring in Purkinje cell dendrites in mouse cerebellar slices. High frequency parallel fibre stimulation (50 Hz, 3,50-times) depolarized Purkinje cells, and Ca2+ transients were observed at the anatomically expected sites. The magnitude of the Ca2+ transients increased linearly with increasing numbers of parallel fibre inputs. With 50 stimuli, Ca2+ transients lasted for seconds, and the peak [Ca2+] reached ,100 µm, which was much higher than that reported previously, although it was still confined to a part of the dendrite. In contrast, Na+ transients were sustained for tens of seconds and diffused away from the stimulated site. Pharmacological interventions revealed that Na+ influx through ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors and Ca2+ influx through P-type Ca channels were essential players, that AMPA receptors did not operate as a Ca2+ influx pathway and that Ca2+ release from intracellular stores through inositol trisphosphate receptors or ryanodine receptors did not contribute greatly to the large Ca2+ transients. [source] NMDA receptor subunits GluR,1, GluR,3 and GluR,1 are enriched at the mossy fibre,granule cell synapse in the adult mouse cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001Kazuyuki Yamada Abstract Cerebellar N -methyl- d -aspartate (NMDA) receptors are concentrated in the granular layer and are involved in motor coordination and the induction of long-term potentiation at mossy fibre,granule cell synapses. In the present study, we used immunohistochemistry to examine the distribution of NMDA receptor subunits in the adult mouse cerebellum. We found that appropriate pepsin pretreatment of sections greatly enhanced the sensitivity and specificity of immunohistochemical detection. As a result, intense immunolabelling for GluR,1 (NR2A), GluR,3 (NR2C), and GluR,1 (NR1) all appeared in synaptic glomeruli of the granular layer. Double immunofluorescence showed that these subunits were colocalized in individual synaptic glomeruli. Within the glomerulus, NMDA receptor subunits were located between centrally-located huge mossy fibre terminals and peripherally-located tiny Golgi axon terminals. By immunoelectron microscopy, all three subunits were detected at the postsynaptic junction in granule cell dendrites, forming synapses with mossy fibre terminals. Consistent with the known functional localization, GluR,1, GluR,3, and GluR,1 are, thus, anatomically concentrated at the mossy fibre,granule cell synapse. By contrast, immunohistochemical signals were very low in Purkinje cell somata and dendrites in the molecular layer. The lack of GluR,1 immunolabelling in Purkinje cells was unexpected because the cells express GluR,1 mRNA at high levels and high levels of GluR,1 protein in the molecular layer were revealed by immunoblot. As Purkinje cells are exceptionally lacking GluR, expression, the discrepant result may provide in vivo evidence suggesting the importance of accompanying GluR, subunits in synaptic localization of GluR,1. [source] Odour-evoked [Ca2+] transients in mitral cell dendrites of frog olfactory glomeruliEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001Kerry Delaney Abstract We measured Ca2+ concentration, [Ca2+], transients in mitral cell distal apical dendritic tufts produced by physiological odour stimulation of the olfactory epithelium and electrical stimulation of the olfactory nerve (ON) using two-photon scanning and conventional wide-field microscopy of Ca2+ -Green-1 dextran in an in vitro frog nose,brain preparation. Weak or strong ON shock-evoked fluorescence transients always had short latency with an onset 0,10 ms after the onset of the bulb local field potential, rapidly increasing to a peak of up to 25% fractional fluorescence change (,F/F) in 10,30 ms, were blocked by 10 µm CNQX, decaying with a time constant of about 1 s. With stronger ON shocks that activated many receptor axons, an additional, delayed, sustained AP5-sensitive component (peak at ,,0.5 s, up to 40% ,F/F maximum) could usually be produced. Odour-evoked [Ca2+] transients sometimes displayed a rapid onset phase that peaked within 50 ms but always had a sustained phase that peaked 0.5,1.5 s after onset, regardless of the strength of the odour or the amplitude of the response. These were considerably larger (up to 150% ,F/F) than those evoked by ON shock. Odour-evoked [Ca2+] transients were also distinguished from ON shock-evoked transients by tufts in different glomeruli responding with different delays (time to onset differed by up to 1.5 s between different tufts for the same odour). Odour-evoked [Ca2+] transients were increased by AMPA-kainate receptor blockade, but substantially blocked by AP5. Electrical stimulation of the lateral olfactory tract (5,6 stimuli at 10 Hz) that evoked granule cell feedback inhibition, blocked 60,100% of the odour-evoked [Ca2+] transient in tufts when delivered within about 0.5 s of the odour. LOT-mediated inhibition was blocked by 10 µm bicuculline. [source] Heterogeneous distribution of AMPA glutamate receptor subunits at the photoreceptor synapses of rodent retinaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2001Iris Hack Abstract In the retina the segregation of different aspects of visual information starts at the first synapse in signal transfer from the photoreceptors to the second-order neurons, via the neurotransmitter glutamate. We examined the distribution of the four AMPA glutamate receptor subunits GluR1,GluR4 at the photoreceptor synapses in mouse and rat retinae by light and immunoelectron microscopy and serial section reconstructions. On the dendrites of OFF-cone bipolar cells, which make flat, noninvaginating contacts postsynaptic at cone synaptic terminals, the subunits GluR1 and GluR2 were predominantly found. Horizontal cell processes postsynaptic at both rod and cone synaptic terminals preferentially expressed the subunits GluR2, GluR2/3 and GluR4. An intriguing finding was the presence of GluR2/3 and GluR4 subunits on dendrites of putative rod bipolar cells, which are thought to signal through the sign-inverting metabotropic glutamate receptor 6, mGluR6. Furthermore, at the rod terminals, horizontal cell processes and rod bipolar cell dendrites showed labelling for the AMPA receptor subunits at the ribbon synaptic site or perisynaptically at their site of invagination into the rod terminal. The wide distribution of AMPA receptor subunits at the photoreceptor synapses suggests that AMPA receptors play an important role in visual signal transfer from the photoreceptors to their postsynaptic partners. [source] Localization of the A kinase anchoring protein AKAP79 in the human hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2000Attila Sík Abstract The phosphorylation state of the proteins, regulated by phosphatases and kinases, plays an important role in signal transduction and long-term changes in neuronal excitability. In neurons, cAMP-dependent protein kinase (PKA), protein kinase C (PKC) and calcineurin (CN) are attached to a scaffold protein, A kinase anchoring protein (AKAP), thought to anchor these three enzymes to specific sites of action. However, the localization of AKAP, and the predicted sites of linked phosphatase and kinase activities, are still unknown at the fine structural level. In the present study, we investigated the distribution of AKAP79 in the hippocampus from postmortem human brains and lobectomy samples from patients with intractable epilepsy, using preembedding immunoperoxidase and immunogold histochemical methods. AKAP79 was found in the CA1, presubicular and subicular regions, mostly in pyramidal cell dendrites, whereas pyramidal cells in the CA3, CA2 regions and dentate granule cells were negative both in postmortem and in surgical samples. In some epileptic cases, the dentate molecular layer and hilar interneurons also became immunoreactive. At the subcellular level, AKAP79 immunoreactivity was present in postsynaptic profiles near, but not attached to, the postsynaptic density of asymmetrical (presumed excitatory) synapses. We conclude that the spatial selectivity for the action of certain kinases and phosphatases regulating various ligand- and voltage-gated channels may be ensured by the selective presence of their anchoring protein, AKAP79, at the majority of glutamatergic synapses in the CA1, but not in the CA2/CA3 regions, suggesting profound differences in signal transduction and long-term synaptic plasticity between these regions of the human hippocampus. [source] Glutamate spillover augments GABA synthesis and release from axodendritic synapses in rat hippocampusHIPPOCAMPUS, Issue 1 2010Misty M. Stafford Abstract Tight coupling between gamma-aminobutyric acid (GABA) synthesis and vesicle filling suggests that the presynaptic supply of precursor glutamate could dynamically regulate inhibitory synapses. Although the neuronal glutamate transporter excitatory amino acid transporter 3 (EAAT3) has been proposed to mediate such a metabolic role, highly efficient astrocytic uptake of synaptically released glutamate normally maintains low-extracellular glutamate levels. We examined whether axodendritic inhibitory synapses in stratum radiatum of hippocampal area CA1, which are closely positioned among excitatory glutamatergic synapses, are regulated by synaptic glutamate release via presynaptic uptake. Under conditions of spatially and temporally coordinated release of glutamate and GABA within pyramidal cell dendrites, blocking glial glutamate uptake enhanced quantal release of GABA in a transporter-dependent manner. These physiological findings correlated with immunohistochemical studies revealing expression of EAAT3 by interneurons and uptake of D-asparate into putative axodendritic inhibitory terminals only when glial uptake was blocked. These results indicate that spillover of glutamate between adjacent excitatory and inhibitory synapses can occur under conditions when glial uptake incompletely clears synaptically released glutamate. Our anatomical studies also suggest that perisomatic inhibitory synapses, unlike synapses within dendritic layers of hippocampus, are not capable of glutamate uptake and therefore transporter-mediated dynamic regulation of inhibition is a unique feature of axodendritic synapses that may play a role in maintaining a homeostatic balance of inhibition and excitation. © 2009 Wiley-Liss, Inc. [source] GluR5,6,7 subunit immunoreactivity on apical pyramidal cell dendrites in hippocampus of schizophrenics and manic depressivesHIPPOCAMPUS, Issue 5 2001Francine M. Benes Abstract Recent postmortem studies have suggested that changes in the regulation of kainate-sensitive glutamate receptors (kainate receptors) in the hippocampus may play a role in schizophrenia. To explore this possibility further, the distribution of immunoreactivity (IR) for the GluR5,6,7 subunits of the KR was assessed in a cohort consisting of 15 normal controls, 15 schizophrenics, and 9 manic depressives matched for age and postmortem interval (PMI). Cross sections of hippocampus showed abundant GluR5,6,7 -IR on apical dendrites of pyramidal neurons in the stratum radiatum and stratum moleculare. In normal controls, both the numerical and length density of IR dendrites were much higher in sector CA2 than in sectors CA3 or CA1. When data for the individual groups were separately examined, the schizophrenics showed a 30,35% reduction in the density of GluR5,6,7 -IR dendrites found in both stratum radiatum and stratum moleculare of sectors CA3 and CA2, as well as proximal and middle portions of CA1. In CA2, the magnitude of this decrease in schizophrenia was 2.5 times larger than that seen in any of the other sectors. For the manic depressive group, no significant differences were observed in any sectors or laminae examined. The potential confounding effects of either age, PMI, or neuroleptic exposure do not explain the reduced density of IR dendrites detected in the schizophrenic group. Taken together, the preferential reduction of GluR5,6,7 -IR observed on apical dendrites of pyramidal neurons is consistent with a functional downregulation of the kainate receptor in the hippocampus of schizophrenic brain. Hippocampus 2001;11:482,491. © 2001 Wiley-Liss, Inc. [source] Expression of SV2 in the Seveloping Chick Cerebellum: Comparison with Calbindin and AMPA Glutamate Receptors 2/3THE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 5 2008Detlev Grabs Abstract The well-organized cerebellum is an ideal model to investigate the developmental appearance and localization of pre- and postsynaptic structures. One of the synaptic proteins abundant in the central nervous system and localized in presynaptic vesicle membranes is the synaptic vesicle protein 2 (SV2). SV2 was shown to be involved in priming and modulating synaptic vesicles and having an effect in epileptic diseases. So far there are no data available describing the developmental localization of this protein in the cerebellum. We followed the expression pattern of SV2 and compared it with the expression of the neuronal calcium-binding protein Calbindin and the AMPA glutamate receptor subunits 2/3 (GluR 2/3), both shown to be early expressed in the developing chick cerebellum predominantly in Purkinje cells. We detected the expression of SV2 in presynaptic terminals (mainly from climbing and mossy fibers) as soon as they are formed at embryonic day 16 in the inner molecular layer. Purkinje cells express Calbindin and GluR 2/3 in the soma and postsynaptically in the primary dendrites at this stage. With ongoing development, the pattern of SV2 expression follows the development of Purkinje cell dendrites in the molecular layer, suggesting a synaptic refinement of labeled climbing and later parallel fibers. Anat Rec, 291:538,546, 2008. © 2008 Wiley-Liss, Inc. [source] Synaptic localization of P2X7 receptors in the rat retinaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 1 2004Theresa Puthussery Abstract The distribution of P2X7 receptor (P2X7R) subunits was studied in the rat retina using a subunit-specific antiserum. Punctate immunofluorescence was observed in the inner and outer plexiform layers. Double labeling of P2X7 and the horizontal cell marker, calbindin, revealed extensive colocalization in the outer plexiform layer (OPL). Significant colocalization of P2X7R and kinesin, a marker of photoreceptor ribbons, was also observed, indicating that this receptor may be expressed at photoreceptor terminals. Furthermore, another band of P2X7R puncta was identified below the level of the photoreceptor terminals, adjacent to the inner nuclear layer (INL). This band of P2X7R puncta colocalized with the active-zone protein, bassoon, suggesting that "synapse-like" structures exist outside photoreceptor terminals. Preembedding immunoelectron microscopy demonstrated P2X7R labeling of photoreceptor terminals adjacent to ribbons. In addition, some horizontal cell dendrites and putative "desmosome-like" junctions below cone pedicles were labeled. In the inner plexiform layer (IPL), P2X7R puncta were observed surrounding terminals immunoreactive for protein kinase C-,, a marker of rod bipolar cells. Double labeling with bassoon in the IPL revealed extensive colocalization, indicating that P2X7R is likely to be found at conventional cell synapses. This finding was confirmed at the ultrastructural level: only processes presynaptic to rod bipolar cells were found to be labeled for the P2X7R, as well as other conventional synapses. These findings suggest that purines play a significant role in neurotransmission within the retina, and may modulate both photoreceptor and rod bipolar cell responses. J. Comp. Neurol. 472:13,23, 2004. © 2004 Wiley-Liss, Inc. [source] | ||||||||||