bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of NMDA and High‐affinity Kainate Receptor Subunit mRNAs in the Adult Rat Retina
Authors: Brandstätter J. H. , Hartveit E. , Sassoè‐Pognetto M. , Wässle H. 
Published: April 2006

AbstractThe expression patterns of nine genes encoding theN‐methyl‐d‐aspartate (NMDA) receptor subunits NR1 and NR2A, NR2B, NR2C and NR2D, and the high‐affinity kainate receptor subunits KA1, KA2, GluR6 and GluR7, were studied in the adult rat retina byin situhybridization. Hybridization with [35S]dATP‐labelled oligonucleotide probes revealed the expression of four of the NMDA receptor subunits (NR1, NR2A, NR2B and NR2C) and three of the high‐affinity kainate receptor subunits (KA2, GluR6 and GluR7) in the retina. The NMDA receptor subunit NR2D and the high‐affinity kainate receptor subunit KA1 could not be detected. In the ganglion cell layer, virtually every ganglion cell or displaced amacrine cell expressed the receptor subunits NR1, NR2A, NR2B, NR2C, KA2 and GluR7. The GluR6 subunit was expressed in a more restricted manner in the ganglion cell layer. In the inner nuclear layer, the receptor subunits NR1 and KA2 were homogeneously distributed, and therefore are most likely expressed by all cell types in this layer. The GluR6, NR2A, NR2B and NR2C subunits were expressed by subsets of amacrine cells. Labelling for NR2C was also found above the middle of the inner nuclear layer, corresponding to the location of bipolar cell somata. The GluR7 subunit was expressed by most amacrine and bipolar cells. These findings suggest that NMDA and high‐affinity kainate receptor subunits could be present at a majority of glutamatergic retinal synapses.
Rat Hippocampal Kindling Induces Changes in the Glutamate Receptor mRNA Expression Patterns in Dentate Granule Neurons
Authors: Kamphuis W. , de Rijk T. C. , Talamini L. M. , Lopes da Silva F. H. 
Published: April 2006

AbstractThe expression level of the mRNAs encoding the Flip and Flop versions of the AMPA‐selective glutamate receptor subunits A, B, C and D was studied usingin situhybridization in the hippocampus of rats kindled by Schaffer collateral/commissural fibre stimulation. The expression levels of the Flip variant of GluR‐A, B and C mRNAs were bilaterally enhanced in the dentate granule neurons of fully kindled animals 24 h after the last seizure. These changes were already observed after the sixth kindling stimulation (preconvulsive‐stage), but not after a single afterdischarge. Four weeks after the last seizure, when the animals were still hypersensitive to kindling stimulations, only GluR‐A Flip expression was enhanced. These results suggest that kindling epileptogenesis is accompanied by an increased number and enhanced sensitivity of the expressed AMPA type glutamate receptors in the fascia dentata, leading to an enhanced excitatory synaptic transmission which may contribute to the process of kindling epileptogenesis.
Neurotrophic Factor Receptors and Their Signal Transduction Capabilities in Rat Astrocytes
Authors: Rudge John S. , Li Yanping , Pasnikowski Elizabeth M. , Mattsson Karen , Pan Li , Yancopoulos George D. , Wiegand Stanley J. , Lindsay Ronald M. , Ip Nancy Y. 
Published: April 2006

AbstractUntil recently, astrocytes were not considered as sites for neurotrophic factor action. We show here that, both in vivo and in vitro, astrocytes express receptors for two separate families of neurotrophic factors. In the intact adult rat CNS, astrocytes express the extracellular domain of the neurotrophin receptor TrkB and, in a more restricted population, the low‐affinity nerve growth factor receptor p75LNGFR. In the lesioned CNS, expression of the alpha component of the receptor for ciliary neurotrophic factor (CNTFRα) switches from a purely neuronal localization to cells in the glial scar at the edge of the wound. Using cultured hippocampal astrocytes as a model to address the functional status of these receptors, we have found only the truncated forms of TrkB and TrkC, which are incapable of signal transduction as measured by protein tyrosine phosphorylation or immediate early gene induction. In contrast, a fully functional CNTF receptor complex capable of signal transduction is present on cultured astrocytes. Thus, the neurotrophin receptors may act primarily to sequester or present the neurotrophins, whereas in the case of CNTF a functional response can be initiated within the astrocyte.
Modular Organization of Human Extrastriate Visual Cortex: Evidence from Cytochrome Oxidase Pattern in Normal and Macular Degeneration Cases
Authors: Clarke Stephanie 
Published: April 2006

AbstractThe human extrastriate occipital cortex contains several visual areas that are probably analogues of macaque areas V2, V3, VP, V4 and V5. Tracing of callosal connections has led to the anatomical identification of these areas and to the characterization of some of them by cyto‐ and myeloarchitecture (Clarke and Miklossy, 1990). The pattern of cytochrome oxidase activity in these visual areas is now described in a normal case and in a case of age‐related bilateral macular degeneration. In normal cortex, the laminar distribution of cytochrome oxidase activity was similar in V2, V3, VP, V4 and V5; a prominent dark band covered most of layers III and IV, and its upper and lower limits were gradual. In V2, V3, V4 and V5 but not VP, layer II tended to be darker than the infragranular layers. The overall intensity of the staining varied between areas: VP was very light, V2, V3 and V4 were darker, and V5 was very dark. A different, two‐band pattern of cytochrome oxidase activity was found in a restricted region of the posterosuperior precuneus. The bilateral age‐related macular degeneration had led to a great loss of ganglion cells in the central, but not in the peripheral retinae. The central representation in the lateral geniculate nuclei showed abnormally weak staining for cytochrome oxidase, particularly in the parvocellular layers. In the cortex, the contrast between lightly and darkly stained regions was greater than in the normal case. In particular, V5 was very heavily stained, and in V1 and V2 there were two different types of dark stripes that may represent compartments driven predominantly by the magnocellular system.
Antisera to Glutathione: Characterization and Immunocytochemical Application to the Rat Cerebellum
Authors: Hjelle Ole P. , Chaudhry Farrukh A. , Ottersen Ole P. 
Published: April 2006

AbstractRabbits were immunized with reduced glutathione (γ‐glutamyl‐cysteinyl‐glycine) coupled to bovine serum albumin by glutaraldehyde or a mixture of glutaraldehyde and formaldehyde. The antisera that were formed were tested qualitatively, by screening them against more than 50 amino acids and peptide conjugates that had been immobilized on cellulose discs (spot test), and quantitatively, by immunogold analysis of test conjugates that had been embedded in an epoxy resin. It was shown that the antisera selectively recognized the reduced and oxidized forms of glutathione and that they did not exhibit any significant crossreactivity with glutamate, cysteine, glycine, γ‐glutamyl‐cysteine or cysteinyl‐glycine. Immunocytochemistry of Vibratome sections of rat cerebellum suggested that glutathione occurs in glial cells as well as in neurons. This was confirmed by electron microscopic, immunogold cytochemistry of tissue from rat cerebellum that had been freeze‐substituted and embedded in Lowicryl under low temperature. Gold particles were concentrated over Golgi epithelial cells and perivascular glial processes, but also occurred over several types of neuronal profile including Purkinje and granule cell bodies, and mossy fibre terminals. At the subcellular level, glutathione‐like immunoreactivity was found in the cytoplasmic matrix, mitochondria and nuclei. The immunolabelling intensity was strongly reduced in animals that had been pretreated with buthionine sulphoximine, which is known to depress the level of glutathione by inhibiting γ‐glutamyl‐cysteine synthetase. The availability of antisera to glutathione is likely to further our understanding of the physiological and pathophysiological roles of this tripeptide.
Selective Allocation of GABAA Receptors Containing the α1 Subunit to Neurochemically Distinct Subpopulations of Rat Hippocampal Interneurons
Authors: Gao B. , Fritschy J. M. 
Published: April 2006

AbstractThe identification of a large variety of GABAA receptor subunits by molecular cloning suggests the existence of multiple receptor subtypes differing in localization and functional properties. In the present study we analysed immunohistochemically the cellular distribution of GABAA receptors containing the α1 subunit in the rat hippocampus with a subunit‐specific antiserum. Prominent staining of numerous interneurons was evident in Ammon's horn and the dentate gyrus, which contrasted with moderate and diffuse immunoreactivity in the dendritic layers of pyramidal and granule cells. Double immunofluorescence staining with antibodies to GABA revealed that a subset of GABAergic neurons in the hippocampus were immunoreactive for the α1 subunit. To determine whether these cells represent distinct subpopulations of interneurons, we analysed the co‐localization of the GABAA receptor α1 subunit with selective markers of hippocampal interneurons (selected calcium‐binding proteins and neuropeptides). In both Ammon's horn and the dentate gyrus, all parvalbumin‐positive neurons and 50% of calretinin‐positive neurons were double‐labelled, whereas interneurons containing calbindin‐D28k were devoid of α1 subunit staining. Similarly, most neurons positive for neuropeptide Y and a subset of somatostatin‐positive cells were double‐labelled, in contrast to cholecystokinin‐ and vasoactive intestinal peptide‐containing cells, which lacked the α1 subunit staining. These results demonstrate cell‐specific expression of GABAA receptors containing the α1 subunit among subsets of hippocampal interneurons, pointing to a pronounced functional specialization of these cells. Furthermore, the prominent expression of GABAA receptors by interneurons suggests that disinhibition may be of major functional relevance in regulating the balance between excitation and inhibition in hippocampal circuits.
Inhibitory Effects of L‐Glutamate on Central Processes of Crustacean Leg Motoneurons
Authors: Pearlstein E. , Marchand A. R. , Clarac F. 
Published: April 2006

AbstractIn crustaceans, glutamatergic excitation at the neuromuscular synapse has been extensively studied. Fewer reports exist of the central and possibly inhibitory actions of glutamate on neurons. The present study analyses the response of intracellularly identified motoneurons, which innervate the proximal leg muscles, to local glutamate pressure applications in the neuropil, in an in vitro thoracic preparation of the crayfish Procambarus clarkii. L‐Glutamate application always inhibited motoneuron activity, with a decrease in input resistance. The resulting depolarization or hyperpolarization could usually be reversed within 10 mV of the resting potential. The response persisted in neurons pharmacologically isolated with Cd2+ or tetrodotoxin. The reversal potential of the response to glutamate was displaced in a low‐chloride solution. Similar responses were obtained with GABA. Application of GABA blocked the glutamate response in a competitive manner. Both responses were suppressed by β‐guanidino‐propionic acid, a competitive antagonist for GABA receptors. This indicates that glutamate activates a chloride‐GABA receptor‐channel. Micromolar concentrations of picrotoxin reduced both the L‐glutamate and the GABA inhibitory responses, thereby unmasking a smaller, picrotoxin‐resistant effect of glutamate (but not of GABA), which was excitatory and sensitive to 6,7‐dinitroquinoxaline‐2,3‐dione (DNQX). These results suggest dual and opposite roles for motoneuron glutamatergic connections–a peripheral (well known) net excitatory one and a central net inhibitory one. Direct inhibition of motoneurons by L‐glutamatergic neurons is to be expected.
Learning‐related Alterations in the Visual Responsiveness of Neurons in a Memory System of the Chick Brain
Authors: Brown M. W. , Horn G. 
Published: April 2006

AbstractThe intermediate and medial hyperstriatum ventrale (IMHV) of the chick brain is known to be essential for the learning process of imprinting. The activity of neurons was recorded from the left IMHV of 2‐day‐old unanaesthetized chicks while the chicks were free to move in a running wheel. The chicks were either raised in complete darkness or visually trained (imprinted) with a set duration of exposure to a visual image. The first group of these birds was trained by exposure for 100 min to a rotating red box and the second was trained by similar exposure to a rotating blue cylinder. A third group was left untrained. Training more than doubled the proportion of sites that responded to the stimulus used to train the bird, relative to the proportion of sites responsive to the other stimulus and to the proportion of sites responsive in the untrained birds; the learning‐related increase was selective and highly significant. Behavioural monitoring indicated that the enhanced responsiveness could not be explained by overt differences in the alertness, attentiveness or movements of the birds. No significant effect of training was found on the proportion of sites responsive to a rotating stuffed jungle fowl or to the sound of a maternal call. The response at certain sites selectively signalled the presence of the training stimulus, while at others the response showed generalization across stimulus shape or colour. There was a non‐specific effect of training upon the pattern of spontaneous discharges of the neurons: the numbers of spikes occurring in clusters (bursts) was significantly reduced in trained birds compared with the dark reared controls.
Naloxone Ameliorates the Learning Deficit Induced by Pentylenetetrazol Kindling in Rats
Authors: Becker Axel , Grecksch Gisela , Brosz Mathias 
Published: April 2006

AbstractEndogenous opioid peptides modulate and regulate processes of central excitability. Furthermore, opioids are thought to interfere with processes of learning and memory storage. In order to study the effects of endogenous opioids on both processes we injected in the course of development of pentylenetetrazol kindling the opiate receptor antagonist naloxone, and tested the animals afterwards in a shuttle‐box task. It was found that naloxone pretreatment had dissociative effects. There was no effect on seizure outcome, whereas the learning deficit was ameliorated in the kindled group. The data suggest that endogenous opioid peptides contribute to the learning deficit found in pentylenetetrazol‐kindled rats.
Homotypic and Heterotypic Coupling Mediated by Gap Junctions During Glial Cell Differentiation In Vitro
Authors: Venance L. , Cordier J. , Monge M. , Zalc B. , Glowinski J. , Giaume C. 
Published: April 2006

AbstractIntercellular communication mediated by gap junctions was investigated during oligodendrocyte differentiation in primary and secondary cell cultures from newborn and adult rats. Two types of communication were considered: ionic coupling and dye‐coupling between similar oligodendrocytes selected at the same stage of differentiation (homotypic) and dye‐coupling between oligodendrocytes and astrocytes (heterotypic), Intercellular diffusion of fluorescent probes and double whole‐cell recordings were used to test the incidence of dye and ionic communication respectively. Progenitor cells, identified with A265 antibodies, were characterized by the absence of ionic and dye‐coupling, whereas oligodendrocytes, identified with galactosylceramide antibodies, exhibited both types of communication. This homotypic coupling was inhibited by various uncoupling agents, but unaffected by treatments which increased the intracellular concentration of CAMP. In cocultures of astrocytes and oligodendrocytes, Lucifer yellow and sulphorhodamine B were exchanged in both directions. This heterotypic dye‐coupling, which could be blocked by octanol, first appeared after 3 weeks in culture and increased to an incidence of 25% after 6 weeks, a developmental pattern comparable to homotypic dye‐coupling between oligodendrocytes. In contrast, during the same period, progenitors and microglia were never observed to be dye‐coupled with astrocytes.
Properties of the Hyperpolarization‐activated Cation Current lh in Rat Midbrain Dopaminergic Neurons
Authors: Mercuri N. B. , Bonci A. , Calabresi P. , Stefani A. , Bernardi G. 
Published: April 2006

abstractIntracellular electrophysiological recordings in current‐ and voltage‐clamp mode were obtained from dopaminergic neurons of the rat mesencephalon in an in vitro slice preparation. In current‐clamp mode, a time‐dependent anomalous rectification (TDR) of the membrane was observed in response to hyperpolarizing current pulses. In single‐electrode voltage‐clamp mode, a slowly developing inward current (lh) underlying the TDR was studied by hyperpolarizing voltage commands from a holding potential of ‐50 to ‐60 mV. lh started to be activated at ‐69 mV, was fully activated at ‐129 to ‐141 mV, with half‐maximal activation at ‐87 mV, and showed no inactivation with time. The time course of development of Ih followed a single exponential, and its time constant was voltage‐dependent. At ‐81 mV, lh activated with a time constant of 379 2 47.6 ms, whereas at ‐129 mV lh activated with a time constant of 65 ? 2.2 ms. Its estimated reversal potential was ‐35 ± 4 mV. Raising the extracellular concentration of K+ from 2.5 to 6.5 and to 12.5 mM increased the amplitude of lh while reducing the extracellular concentration of Na+ from 153.2 to 27.2 mM caused a reduction in amplitude of lh. Bath application of caesium (1–5 mM) reversibly reduced or blocked the TDR/lh. Perfusion of tetrodotoxin (0.5–1 μM), tetraethylammonium (10–20 mM) or barium (0.3–2 mM) did not significantly affect lh. lh was also present in cells impaled with CsCI‐filled electrodes. When lh was substantially reduced by extracellular caesium (1 mM) the firing rate of the dopaminergic cells, which consisted of a spontaneous pacemaker discharge of action potentials, was not clearly changed. In addition, the holding current in voltage‐clamp experiments at ‐50 to ‐60 mV was not affected by 1 mM caesium. We conclude that although the lh current is a typical feature of the dopaminergic neurons, it is neither a significant factor underlying the spontaneous pacemaker activity nor does it contribute substantially to the setting of the normal resting potential level of the membrane. On the other hand, since lh starts at voltages lower than or equal to ‐69 mV (below firing threshold), it may play a modulatory role in the cell's excitability by limiting the amplitude and duration of any prolonged hyperpolarizing events in the dopaminergic cells.
Shape and Spatial Distribution of Receptive Fields and Antagonistic Motion Surrounds in the Middle Temporal Area (V5) of the Macaque
Authors: Raiguel S. , Van Hulle M. M. , Xiao D.‐K. , Marcar V. L. , Orban G. A. 
Published: April 2006

AbstractThe spatial organization of receptive fields in the middle temporal (MT) area of anaesthetized and paralysed macaque monkeys was studied. In all, 288 neurons were successfully recorded. The size and shape of the receptive field (RF) was mapped with small patches of translating random dots and the resulting data were fitted with a generalized Gaussian. Results show that the RF area increases with eccentricity, and is larger in lamina 5 than in other layers. Most of these RFs are elongated, and the axis of elongation tends to be orthogonal to the preferred direction of motion. The direction selectivity is maintained in all positions in the RF, but layer 5 cells are less direction‐selective than cells in other layers. In a second series of experiments, radial dimensions of the classical RF and the antagonistic surround were estimated from area summation tests. These data were fitted with the difference of the integrals of two Gaussians. Surrounds were weakest in layer 4 and strongest in layer 2. Optimal stimulus diameters, also estimated from the area summation curve, were larger in the infragranular layers than in the other layers. The maximum sensitivity of the surround was clearly displaced from the classical RF (CRF) centre, indicating that the surround is not concentric with the CRF. This radial offset and the extent of the surround were largest in layers 2 and 5 and smallest in 3a. The extent of the surround half‐height equalled, on average, 3–4 times that of the CRF. These results suggest that antagonistic surrounds are constructed in MT, probably through horizontal connections, and that a strong vertical organization exists in area MT, as has been shown for V1.
Native Nicotinic Acetylcholine Receptors in Human Imr32 Neuroblastoma Cells: Functional, Immunological and Pharmacological Properties
Authors: Gotti C. , Briscini L. , Verderio C. , Oortgiesen M. , Balestra B. , Clementi F. 
Published: April 2006

AbstractIMR32 cells express two classes of surface nicotinic receptors: those labelled with high affinity by [125I]neuronal toxin, and those labelled by [125Iα‐bungarotoxin. Whole‐cell patch‐clamp recordings indicate that both classes of receptor are able to elicit inward currents that are totally blocked by d‐tubocurarine but only partially blocked by α‐bungarotoxin. In IMR32 cells, nicotine induces an increase in the intracellular level of free Ca2+. This increase, which is also completely blocked by d‐tubocurarine and only partially blocked by α‐bungarotoxin and Cd2+, is due to extracellular calcium influx through both the nicotinic receptors and the voltage‐activated Ca2+ channels. By using subunit‐specific polyclonal antibodies, we have demonstrated that the α‐bungarotoxin receptors contain the α7 subunit, but none of the other subunits whose transcripts are present in IMR32 cells. The pharmacological profile of these human α7‐containing α‐bungarotoxin receptors is similar to that observed in the native chick α7 receptor, but there are also some species‐specific differences.
The Double‐ticker: An Improved Fast Drug‐application System Reveals Desensitization of the Glutamate Channel from a Closed State
Authors: Tour O. , Parnas H. , Parnas I. 
Published: April 2006

AbstractThe present study describes a modification of the fast drug‐application technique (ticker) which combines two fast‐application systems, ‘the double‐ticker’. With the double‐ticker, drugs can be applied to excised patches from either one of the tickers permitting switching among three different solutions in the sub‐millisecond range. We made use of this advantageous feature of the double‐ticker to study two aspects of the glutamate receptor channel in crayfish muscle. The first concerns revealing the number of glutamate binding sites from measurements of a dose‐response relation (2–3 sites). The other relates to the state from which the receptor undergoes desensitization. For the quisqualate‐sensitive glutamate receptor desensitization occurs from a closed state. This is in addition to desensitization from an open state.