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Rat Neocortex (rat + neocortex)
Selected AbstractsMulti-directional differentiation of doublecortin- and NG2-immunopositive progenitor cells in the adult rat neocortex in vivoEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Yasuhisa Tamura Abstract In the adult mammalian brain, multipotent stem or progenitor cells involved in reproduction of neurons and glial cells have been well investigated only in very restricted regions; the subventricular zone of the lateral ventricle and the dentate gyrus in the hippocampal formation. In the neocortex, a series of in vitro studies has suggested the possible existence of neural progenitor cells possessing neurogenic and/or gliogenic potential in adult mammals. However, the cellular properties of the cortical progenitor cells in vivo have not been fully elucidated. Using 5,-bromodeoxyuridine labeling and immunohistochemical analysis of cell differentiation markers, we found that a subpopulation of NG2-immunopositive cells co-expressing doublecortin (DCX), an immature neuron marker, ubiquitously reside in the adult rat neocortex. Furthermore, these cells are the major population of proliferating cells in the region. The DCX(+)/NG2(+) cells reproduced the same daughter cells, or differentiated into DCX(+)/NG2(,) (approximately 1%) or DCX(,)/NG2(+) (approximately 10%) cells within 2 weeks after cell division. The DCX(+)/NG2(,) cells were also immunopositive for TUC-4, a neuronal linage marker, suggesting that these cells were committed to neuronal cell differentiation, whereas the DCX(,)/NG2(+) cells showed faint immunoreactivity for glutathione S-transferase (GST)-pi, an oligodendrocyte lineage marker, in the cytoplasm, suggesting glial cell lineage, and thereafter the cells differentiated into NG2(,)/GST-pi(+) mature oligodendrocytes after a further 2 weeks. These findings indicate that DCX(+)/NG2(+) cells ubiquitously exist as ,multipotent progenitor cells' in the neocortex of adult rats. [source] Organization of GABAA receptor ,-subunit clustering in the developing rat neocortex and hippocampusEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2004B. Hutcheon Abstract We compared the expression and co-expression of ,1, ,2, ,3, and ,5-subunit protein clusters of the ,-aminobutyric acid (GABA)A receptor in the neocortex and hippocampus of rat at postnatal days (PND) 5,10 and 30,40 in order to understand how inhibitory receptors reorganize during brain maturation. The size, intensity, density and pattern of co-localization of fluorescently tagged subunit clusters were determined in deconvolved digital images using a novel 2D cross-correlational analysis. The cross-correlation analysis allowed an unbiased identification of GABAA receptor subunit clusters based on staining intensity. Cluster size increased through development; only the ,2 clusters in dentate gyrus (DG) decreased in size. ,5-subunit cluster density either increased or decreased with maturation depending on the brain region. For the other subunits, the cluster density remained rather constant, with noted exceptions (increase in ,2 clusters in cortical layer 5 but a decrease of ,3 clusters in hilus). The co-localization of ,1-subunit with the others was unique and not correlated to overall changes in subunit abundance between developmental époques. So, although ,2-subunit expression went up in the DG, the clusters became less co-localized with ,1. In contrast, ,5-subunit clusters became more co-localized with ,1 as the ,5-subunit expression declined in cortex and CA1. The co-localization of ,3 with ,1 also became greater in layer 6. In the adult brain not all clustering was associated with synapses, as many ,-subunit clusters did not co-localize with synaptophysin. Overall, these data indicate that the regulation of GABAA receptor clustering is both synaptic and extrasynaptic, presumably reflecting complex cellular trafficking mechanisms. [source] Involvement of post-synaptic kainate receptors during synaptic transmission between unitary connections in rat neocortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003Afia B. Ali Abstract The properties of functional kainate receptor-mediated EPSCs were studied in acute slices from 19,35-day-old rats. EPSCs elicited in pyramidal and fast-spiking cells in layers 2/3 and 5 of the rat motor cortex by extracellular single shock stimulus in the presence of GYKI 53655 and D-2-amino-5-phosphopentanoic resulted in a residual current. This current was not enhanced by cyclothiazide but was blocked by 6-cyano-7-nitroquinoxalin-2,3-dione and is thought to be mediated by kainate receptors. These kainate receptor-mediated currents displayed a wide range of time courses depending on which pre-synaptic fibres were activated. With paired recordings, unitary EPSCs elicited in pyramidal cells were almost totally blocked by GYKI 53655 and D-2-amino-5-phosphopentanoic. However, when L-transpyrrolidine-2,4-dicarboxylate (PDC), a glutamate uptake blocker, was introduced in the bath, the amplitude of kainate receptor-mediated currents, which is resistant to GYKI 53655 and D-2-amino-5-phosphopentanoic, was revealed. The rise and decay time constants of the kainate receptor-mediated currents were identical to control EPSCs. PDC was not required to reveal the kainate receptor-mediated currents elicited in fast-spiking cells which also displayed similar rise and decay time constants to the control EPSCs. Excitatory input onto pyramidal and fast-spiking cells in the neocortex mediated by kainate receptors contributed between 14 and 40% of the total control unitary EPSCs which displayed identical time courses to the AMPA receptor-mediated component of the EPSCs. Post-synaptic kainate receptors at connected pyramidal cell synapses may be located extra-synaptically. [source] Innervation of interneurons immunoreactive for VIP by intrinsically bursting pyramidal cells and fast-spiking interneurons in infragranular layers of juvenile rat neocortexEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2002Jochen F. Staiger Abstract Cortical columns contain specific neuronal populations with characteristic sets of connections. This wiring forms the structural basis of dynamic information processing. However, at the single-cell level little is known about specific connectivity patterns. We performed experiments in infragranular layers (V and VI) of rat somatosensory cortex, to clarify further the input patterns of inhibitory interneurons immunoreactive (ir) for vasoactive intestinal polypeptide (VIP). Neurons in acute slices were electrophysiologically characterized using whole-cell recordings and filled with biocytin. This allowed us to determine their firing pattern as regular-spiking, intrinsically bursting and fast-spiking, respectively. Biocytin was revealed histochemically and VIP immunohistochemically. Sections were examined for contacts between the axons of the filled neurons and the VIP-ir targets. Twenty pyramidal cells and five nonpyramidal (inter)neurons were recovered and sufficiently stained for further analysis. Regular-spiking pyramidal cells displayed no axonal boutons in contact with VIP-ir targets. In contrast, intrinsically bursting layer V pyramidal cells showed four putative single contacts with a proximal dendrite of VIP neurons. Fast-spiking interneurons formed contacts with two to six VIP neurons, preferentially at their somata. Single as well as multiple contacts on individual target cells were found. Electron microscopic examinations showed that light-microscopically determined contacts represent sites of synaptic interactions. Our results suggest that, within infragranular local cortical circuits, (i) fast-spiking interneurons are more likely to influence VIP cells than are pyramidal cells and (ii) pyramidal cell input probably needs to be highly convergent to fire VIP target cells. [source] Possible promotion of neuronal differentiation in fetal rat brain neural progenitor cells after sustained exposure to static magnetismJOURNAL OF NEUROSCIENCE RESEARCH, Issue 11 2009Noritaka Nakamichi Abstract We have previously shown significant potentiation of Ca2+ influx mediated by N-methyl- D -aspartate receptors, along with decreased microtubules-associated protein-2 (MAP2) expression, in hippocampal neurons cultured under static magnetism without cell death. In this study, we investigated the effects of static magnetism on the functionality of neural progenitor cells endowed to proliferate for self-replication and differentiate into neuronal, astroglial, and oligodendroglial lineages. Neural progenitor cells were isolated from embryonic rat neocortex and hippocampus, followed by culture under static magnetism at 100 mT and subsequent determination of the number of cells immunoreactive for a marker protein of particular progeny lineages. Static magnetism not only significantly decreased proliferation of neural progenitor cells without affecting cell viability, but also promoted differentiation into cells immunoreactive for MAP2 with a concomitant decrease in that for an astroglial marker, irrespective of the presence of differentiation inducers. In neural progenitors cultured under static magnetism, a significant increase was seen in mRNA expression of several activator-type proneural genes, such as Mash1, Math1, and Math3, together with decreased mRNA expression of the repressor type Hes5. These results suggest that sustained static magnetism could suppress proliferation for self-renewal and facilitate differentiation into neurons through promoted expression of activator-type proneural genes by progenitor cells in fetal rat brain. © 2009 Wiley-Liss, Inc. [source] Modulation and function of the autaptic connections of layer V fast spiking interneurons in the rat neocortexTHE JOURNAL OF PHYSIOLOGY, Issue 12 2010William M. Connelly Neocortical fast-spiking (FS) basket cells form dense autaptic connections that provide inhibitory GABAergic feedback after each action potential. It has been suggested that these autaptic connections are used because synaptic communication is sensitive to neuromodulation, unlike the voltage-sensitive potassium channels in FS cells. Here we show that layer V FS interneurons form autaptic connections that are largely perisomatic, and without perturbing intracellular Cl, homeostasis, that perisomatic GABAergic currents have a reversal potential of ,78 ± 4 mV. Using variance,mean analysis, we demonstrate that autaptic connections have a mean of 14 release sites (range 4,26) with a quantal amplitude of 101 ± 16 pA and a probability of release of 0.64 (Vcommand=,70 mV, [Ca2+]o= 2 mm, [Mg2+]o= 1 mm). We found that autaptic GABA release is sensitive to GABAB and muscarinic acetylcholine receptors, but not a range of other classical neuromodulators. Our results indicate that GABA transporters do not regulate FS interneuron autapses, yet autaptically released GABA does not act at GABAB or extrasynaptic GABAA receptors. This research confirms that the autaptic connections of FS cells are indeed susceptible to modulation, though only via specific GABAergic and cholinergic mechanisms. [source] Differential inhibitory effects of drugs acting at the noradrenaline and 5-hydroxytryptamine transporters in rat and human neocortical synaptosomes,BRITISH JOURNAL OF PHARMACOLOGY, Issue 7 2009M Mantovani Background and purpose:, Although the amino acid sequences of rat and human 5-hydroxytryptamine (5-HT) and noradrenaline (NA) transporters (i.e. SERT and NET) are highly homologous, species differences exist in the inhibitory effects of drugs acting at these transporters. Therefore, comparison of the potencies of drugs acting at SERT and NET in native human and rat neocortex may serve to more accurately predict their clinical profile. Experimental approach:, Synaptosomes prepared from fresh human and rat neocortical tissues were used for [3H]-5-HT and [3H]-NA saturation and competition uptake experiments. The drugs tested included NA reuptake inhibitors (desipramine, atomoxetine and (S,S)-reboxetine), 5-HT reuptake blockers (citalopram, fluoxetine and fluvoxamine) and dual 5-HT/NA reuptake inhibitors (duloxetine and milnacipran). Key results:, In saturation experiments on synaptosomal [3H]-5-HT and [3H]-NA uptake, the dissociation constants did not indicate species differences although a smaller density of both SERT and NET was observed in human tissues. In competition experiments with the various drugs, marked species differences in their potencies were observed, especially at SERT. The rank order of selectivity ratios (SERT/NET) in human neocortex was as follows: citalopram , duloxetine = fluvoxamine , fluoxetine > milnacipran > desipramine = atomoxetine > (S,S)-reboxetine. Significant species differences in these ratios were observed for duloxetine, atomoxetine and desipramine. Conclusions and implications:, This study provides the first compilation of drug potency at native human neocortical SERT and NET. The significant species differences (viz., human vs. rat) in drug potency suggest that the general use of rodent data should be limited to predict clinical efficacy or profile. [source] | ||||||||||