bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationships of the Dendritic Arborizations of Ventral Striatomesencephalic Projection Neurons With Boundaries of Striatal Compartments. An In Vitro Intracellular Labelling Study in the Rat
Authors: Arts Monique P. M. , Groenewegen Henk J. 
Published: April 2006

AbstractWe studied the relationships of the dendrites of ventral striatomesencephalic projection neurons with the compartmental structure of the ventral striatum, as revealed by enkephalin immunohistochemistry. Lightly fixed slices were employed in which Lucifer yellow was intracellulary injected into neurons that were retrogradely labelled following Fast Blue injections in the ventral tegmental area. Double immunohistochemical staining was carried out using antisera to Lucifer yellow and Leu‐enkephalin. Most of the 226 injected cells were located in the core region of the nucleus accumbens. All these neurons were of the small‐ to medium‐sized spiny type. The dendritic arborizations of over 90% of the cells remained within the compartment in which the parent cell bodies resided. The dendrites of most of these neurons abutted the border of the compartment, whereas a smaller number of neurons had dendrites that were distant from any compartmental boundary. The dendrites of fewer than 10% of the neurons crossed the borders of compartments. Only a few cells were injected in the shell region of the nucleus accumbens. None of these neurons extended its dendrites into the core region of the nucleus or into the territory of the clusters of small cells which characterize the shell. The present results demonstrate that the dendrites of the great majority of ventral striatomesencephalic neurons comply with the boundaries of ventral striatal enkephalin compartments. Together with the results of previous studies showing that such compartments are selectively innervated by thalamic and cortical afferents, and have outputs to different areas in the ventral mesencephalon, the present data suggest the existence of discrete channels through the ventral striatum.
Transient Association of the HNK‐1 Epitope with 5′‐Nucleotidase during Development of the Cat Visual Cortex
Authors: Vogel M. , Zimmermann H. , Singer W. 
Published: April 2006

AbstractDuring early postnatal development of the kitten visual cortex the ectoenzyme 5′‐nucleotidase undergoes a characteristic redistribution. Until about postnatal week 6 it is essentially confined to synaptic contacts in input layer IV and its expression is related to the use‐dependent segregation of thalamic afferents into ocular dominance columns. Subsequently, 5′‐nucleotidase becomes distributed uniformly throughout all layers and is then associated selectively with glial cells. Here we describe an age‐dependent alteration in the expression of a carbohydrate epitope of 5′‐nucleotidase which correlates with the developmental change of the enzyme's localization. We have isolated 5′‐nucleotidase from the occipital cortex of kittens of varying age and from adult cats and investigated by immunoblotting the association of the HNK‐1 carbohydrate epitope with the protein. 5′‐Nucleotidase carries the HNK‐1 epitope in kittens of 3–9 weeks but the epitope is absent from 12‐week‐old kittens or adult cats. Thus, the appearance of the HNK‐1 epitope correlates with the transient localization of the enzyme at synapses. The HNK‐1 carrying 5′‐nucleotidase may be involved in synaptogenesis and use‐dependent modifications of synaptic connections.
Brain‐derived Neurotrophic Factor is a Survival Factor for Cultured Rat Cerebellar Granule Neurons and Protects them Against Glutamate‐induced Neurotoxicity
Authors: Lindholm Dan , Dechant Georg , Heisenberg Carl‐Philipp , Thoenen Hans 
Published: April 2006

AbstractWe have studied the effects of different neurotrophins on the survival and proliferation of rat cerebellar granule cells in culture. These neurons express trkB and trkC, the putative neuronal receptors for brain‐derived neurotrophic factor (BDNF) and neurotrophin‐3 (NT‐3) respectively. Binding studies using iodinated BDNF and NT‐3 demonstrated that both BDNF and NT‐3 bind to the cerebellar granule neurons with a similar affinity of ˜ 2x10‐9 M. The number of receptors per granule cell was surprisingly high, ∼30x10‐4 and 2x 105 for BDNF and NT‐3, respectively. Both NT‐3 and BDNF elevated c‐fos mRNA in the granule neurons, but only BDNF up‐regulated the mRNA encoding the low‐affinity neurotrophin receptor (p75). In contrast to NT‐3, BDNF acted as a survival factor for the granule neurons. BDNF also induced sprouting of the granule neurons and significantly protected them against neurotoxicity induced by high (1 mM) glutamate concentrations. Cultured granule neurons also expressed low levels of BDNF mRNA which were increased by kainic acid, a glutamate receptor agonist. Thus, BDNF, but not NT‐3, is a survival factor for cultured cerebellar granule neurons and activation of glutamate receptor(s) up‐regulates BDNF expression in these cells.
Sodium, Calcium and Late Potassium Currents are Reduced in Cerebellar Granule Cells Cultured in the Presence of a Protein Complex Conferring Resistance to Excitatory Amino Acids
Authors: Zona Cristina , Ragozzino Davide , Ciotti Maria Teresa , Mercanti Delio , Avoli Massimo , Brancati Aldo , Calissano Pietro 
Published: April 2006

AbstractWhole‐cell, patch‐clamp recordings were used to study voltage‐gated currents generated by cerebellar granule cells that were cultured in medium containing either 10% fetal calf serum (hereafter termed S + granules) or neurite outgrowth and adhesion complex (NOAC, hereafter called NOAC granules). NOAC is a protein complex found in rabbit serum that renders granules resistant to the excitotoxic action of excitatory amino acids. During depolarizing commands both S+ and NOAC granules generated Na+ and Ca2+ inward currents and an early and a late K+ outward currents. However, Na+ and Ca2+ Inward currents and late outward K+ currents recorded in NOAC granules were smaller than those seen in S+ granules. Furthermore, although of similar amplitude, early K+ currents displayed different kinetics in the two types of neurons. Thus, these data demonstrate that the electrophysiological properties of cerebellar granules, and probably of other neuronal populations, depend upon serum components and raise the possibility that an analogous modulation might be operative in vivo, and play a role in development, synaptic plasticity or neuropathological processes.
Stochastic Geometry and Electrotonic Architecture of Dendritic Arborization of Brain Stem Motoneuron
Authors: Bras H. , Korogod S. , Driencourt Y. , Gogan P. , Tyc‐Dumont S. 
Published: April 2006

AbstractWe describe how the stochastic geometry of dendritic arborization of a single identified motoneuron of the rat affects the local details of its electrotonic structure. After describing the 3D dendritic geometry at high spatial resolution, we simulate the distribution of voltage gradients along dendritic branches under steady‐state and transient conditions. We show that local variations in diameters along branches and asymmetric branchings determine the non‐monotonous features of the heterogeneous electrotonic structure. This is defined by the voltage decay expressed as a function of the somatofugal paths in physical distances (voltage gradient). The fan‐shaped electrotonic structure demonstrates differences between branches which are preserved when simulations are computed from different values of specific membrane resistivity although the absolute value of their voltages is changed. At given distances from soma and over long paths, some branches display similar voltages resulting in their grouping which is also preserved when specific membrane resistivity is changed. However, the mutual relation between branches inside the group is respecified when different values of specific membrane resistivity are used in the simulations. We find that there are some invariant features of the electrotonic structure which are related to the geometry and not to the electrical parameters, while other features are changed by altering the electrical parameters. Under transient conditions, the somatofugal invasion of the dendritic tree by a somatic action potential shifts membrane potentials (above 10 mV) of dendritic paths for unequal distances from the soma during several milliseconds. Electrotonic reconfigurations and membrane shifts might be a mechanism for postsynaptic plasticity.
Antisense Probes Against Mediatophore Block Transmitter Release in Oocytes Primed with Neuronal mRNAs
Authors: Cavalli Antonella , Dunant Yves , Leroy Christine , Meunier François‐Marie , Morel Nicolas , Israël Maurice 
Published: April 2006

AbstractAntisense oligodesoxynucleotides were used to determine whether the mediatophore proteolipid is necessary for the Ca2+‐dependent release of the neurotransmitter acetylcholine. Xenopus laevis oocytes were injected with poly(A)+ mRNAs extracted from the electric lobes of Torpedo marmorata. The electric lobes contain an homogeneous population of cholinergic neurons homologous to motoneurons. Addition of antisense probes hybridizing to the mediatophore 15 kDa subunit inhibited the expression of both the mediatophore proteolipid in oocyte membranes and the Ca2+‐dependent acetylcholine release. Expression of other neuronal functions such as synthesis of [14C]acetylcholine from [14C]acetate was not inhibited. Another antisense probe specific for the sequence of a related proteolipid cDNA (the 15 kDa subunit of the chromaffin granule protonophore) was used as a control. It did not hybridize with the Torpedo mediatophore mRNA and, injected in addition to electric lobe mRNAs, it did not inhibit either mediatophore expression or acetylcholine release. We showed in addition that the mRNA primed oocytes did not contain a vesicular pool of acetylcholine. It was concluded (i) that the mediatophore proteolipid is essential for Ca2+‐dependent acetylcholine release and (ii) that the cytosolic pool of neurotransmitter seems to be preferentially used in this system.
Low Doses of NMDA Receptor Antagonists Synergistically Increase the Anticonvulsant Effect of the AMPA Receptor Antagonist NBQX in the Kindling Model of Epilepsy
Authors: Löscher Wolfgang , Rundfeldt Chris , Hönack Dagmar 
Published: April 2006

AbstractExcitatory amino acid transmitters are involved in the initiation of seizures and their propagation. Most attention has been directed to synapses using N‐methyl‐d‐aspartate (NMDA) receptors, although more recent evidence indicates potential roles for the a‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors as well. In the present experiments in amygdala‐kindled rats, i.e. a model of partial epilepsy, competitive and uncompetitive NMDA antagonists exerted only weak anticonvulsant effects, whereas the AMPA antagonist 2,3‐dihydroxy‐6‐nitro‐7‐sulfamoylbenzo(F)quinoxaline (NBQX) potently increased focal seizure threshold and inhibited seizure spread from the focus. These effects of NBQX were dramatically increased by pretreatment with low doses of NMDA antagonists, whereas adverse effects of NBQX were not potentiated. These data suggest that both non‐NMDA and NMDA receptors are critically involved in the kindled state, and that combinations of AMPA and NMDA receptor antagonists provide a new strategy for treatment of epileptic seizures.
Functional and Structural Topography of Horizontal Inhibitory Connections in Cat Visual Cortex
Authors: Kisvárday Zoltán F. , Eysel Ulf T. 
Published: April 2006

AbstractThe functional organization of long‐horizontal inhibitory connections was studied in cat visual cortical area 17, using a combination of electrophysiological recording and anatomical tracing in the same tissue. Orientation maps were obtained by recording multiunit activity from layer III at regular intervals (100–300μm) in a region of ‐1.3 mm2 of cortex at a depth corresponding to the location of the basket cell axons reconstructed later. Before the physiological mapping, the neuronal tracer biocytin had been iontophoretically injected at one functionally characterized site. On the basis of light microscopic features a total of five biocytin‐labelled large basket axons, BC1 ‐ BC5, were reconstructed from series of horizontal sections of two cats. The parent somata and dendritic fields of three axons (BC1, BC4 and BC5) could also be reconstructed. The axonal field of basket cell BC1 had an overall lateral spread of 1.8 mm. The axons of basket cells BC4 and BC5 spanned a distance of 3.05 and 2.85 mm, respectively. The distribution pattern of histologically reconstructed recording sites and of five labelled basket cell axons were directly compared in the same sections. The results show that a single large basket cell provides input to regions representing the whole range of orientations, i.e. iso‐orientation (±30°), oblique orientation (±[30–60]°) and cross‐orientation (±[60–90]°) to that at the basket cell's soma. Furthermore, the differential effect mediated by the same large basket cell at sites of different orientation preference was numerically estimated for two basket cells (BC4 and BC5) whose preferred orientations could be determined on the basis of recording sites adjacent to their parent somata. We counted the number of axonal terminals of these basket cells at iso‐, oblique‐ and cross‐orientation sites and found no significant difference in the average density of terminals at sites of either orientation preference. The functional topography of large basket cell axons indicates that the same basket cell can mediate iso‐, oblique‐ and cross‐orientation inhibition at different sites. Hence, we assume that large basket cells serve a complex physiological role depending on the location of target cells in the orientation map.
Regional Distribution of Putative NPY Y1 Receptors and Neurons Expressing Y1 mRNA in Forebrain Areas of the Rat Central Nervous System
Authors: Larsen Philip J. , Sheikh Søren P. , Jakobsen Cherine R. , Schwartz Thue W. , Mikkelsen Jens D. 
Published: April 2006

AbstractUsing monoiodinated radioligands of peptide YY (PYY), and the recently introduced neuropeptide Y (NPY) analogue [Leu31,Pro34]NPY, receptor binding sites of the Y1 and Y2 type were localized in the rat brain by quantitative in vitro autoradiography. The binding specificity and affinity of both radiolabeled ligands were analysed by ligand binding studies employing rat brain membrane homogenates from cerebral cortex and hippocampus. Using in situ hybridization histochemistry, the regional distribution and cellular localization of mRNA encoding the Y1 receptor were investigated in rat brain sections and compared to the distribution of Y1‐specific binding sites. PYY binds to both Y1 and Y2 receptors, while long C‐terminal fragments such as NPY13–36 and NPY16–36 bind preferentially to Y2 receptors. [Leu31, Pro34]NPY is a specific agonist for Y1 receptors. Highest densities of [125I]PYY binding sites were found in the cerebral cortex, the thalamus, the lateral septum, the hippocampus and the mesencephalic dopaminergic areas. In order to block putative Y2 receptors, a series of [125I]PYY binding experiments was performed in the presence of NPY13–36 (1 μM), a Y2 preferring C‐terminal fragment. High densities of binding sites remained present in the cerebral cortex, the thalamus and the medial mammillary nucleus when NPY13–36 was present in the incubation medium. Furthermore, these areas were highly enriched with [125l][Leu31, Pro34]NPY binding sites. In contrast, the hippocampal complex had its binding capacity reduced by ‐50%, while the lateral septum and mesencephalic dopaminergic areas had their binding capacities reduced even further. Linear regression analysis showed a high degree of correspondence between [125l][Leu31, Pro34]NPY binding and that obtained with [125I]PYY in the presence of 1 μM NPY13–36, suggesting that the two independent approaches to visualizing Y1 binding sites are comparable. In situ hybridization histochemistry revealed high levels of Y1 mRNA in the granular cell layer of the hippocampal dentate gyrus, several thalamic nuclei and the hypothalamic arcuate nucleus. Moderate levels of Y1 mRNA were seen in the frontoparietal cortex, several thalamic nuclei, the hippocampal pyramidal layers, the subiculum, the olfactory tubercle, the claustrum and a number of hypothalamic nuclei. The mesencephalon, the amygdala and most basal ganglia showed very low levels of hybridization. The present study further clarifies the anatomical distribution of multiple NPY binding sites within the central nervous system of the rat, and extends earlier suggestions that Y1 and Y2 receptor types are present within the central nervous system.
Mouse Barrel Cortex Functionally Compensates for Deprivation Produced by Neonatal Lesion of Whisker Follicles
Authors: Melzer Peter , Crane Alison M. , Smith Carolyn B. 
Published: April 2006

AbstractIn the murine somatosensory pathway, the metabolic whisker map in barrel cortex derived with the autoradiographic deoxyglucose method is spatially in register with the morphological whisker map represented by the barrels. The barrel cortex of adult mice, in which we had removed three whisker follicles from the middle row of whiskers shortly after birth, contained a disorganized zone surrounded by enlarged barrels with partially disrupted borders. With the fully quantitative autoradiographic deoxyglucose method, we investigated in barrel cortex of such mice the magnitude and the pattern of metabolic responses evoked by the deflection of whiskers. Most remarkably, the simultaneous deflection of six whiskers neighbouring the lesion activated not only the territory of the corresponding barrels, but also the unspecifiable area intercalated between the clearly identified barrels. This metabolic whisker map, unpredictable from the morphological ‘barrel’ map, may reflect a functional compensation for the deficit in input.
Precision and Variability in Postsynaptic Target Selection of Inhibitory Cells in the Hippocampal CA3 Region
Authors: Gulyás Attila I. , Mlles Richard , Hájos Norbert , Freund Tamás F. 
Published: April 2006

AbstractNon‐pyramidal cells were filled intracellularly with biocytin in the CA3 region of the guinea‐pig hippocampus in vitro, within or close to stratum pyramidale. On the basis of camera lucida reconstructions and electron microscopy, six different cell types with distinct laminar distribution of axon terminals could be distinguished. The axon of three axo‐axonic cells, three typical basket cells, and atypical basket cells of two types arborized in the perisomatic and proximal dendritlc region of CA3 pyramidal cells. Two cells with axons innervating the distal dendritlc segments of pyramidal cells were also found; one terminated in stratum radiatum and the other in stratum lacunosum‐moleculare. Electron microscopy demonstrated that symmetrical synapses were formed by the labelled boutons on axon initial segments, somata, and proximal or distal dendrites of mostly pyramidal neurons. Axo‐axonic cells showed absolute target selectivity for axon initial segments, whereas for the other cells the distribution of contacted elements was determined by the laminar distribution of axon terminals. In two cases, where additional cells were labelled with biocytin, multiple (up to nine) light microscopically identified contacts (presumed synaptic contacts) were established by the interneurons on several pyramidal cells and on an axo‐axonic cell. Our results show that a restricted set of inhibitory cells, with somata within or close to CA3 stratum pyramldale, possess variable patterns of axonal arborization. Various types of postsynaptic elements are contacted, but precision in selecting certain targets and ignoring others is maintained within a particular cell type and layer. In contrast to the diversity of axonal arbors the structure of the dendritic trees shows no consistent differences, suggesting that the cells may be activated by a similar set of afferents. It seems probable that the innervation of precise regions of postsynaptic pyramidal cells by different types of interneurons–often in conjunction with particular excitatory afferents (Han et at., Eur. J. Neurosci., 5, 395–410, 1993)–underlies functional differences in inhibitory synaptic actions.
Loss of Layer‐specific Astrocytic Glutamine Synthetase Immunoreactivity in Slice Cultures of Hippocampus
Authors: Derouiche Amin , Heimrich Bernd , Frotscher Michael 
Published: April 2006

AbstractGlutamine synthetase (GS) supposedly inactivates the excitatory neurotransmitter glutamate. By using immunocytochemistry for GS, we recently demonstrated a layer‐specific, perisynaptic distribution of GS‐immunoreactive astrocytes and their processes in perfusion‐fixed rat hippocampi. Highest levels of immunoreactivity were found in well defined termination zones of glutamatergic hippocampal afferents. In the present study we analysed the developmental aspect of this neuron – glia interaction by using hippocampal slice cultures lacking all extrinsic afferents. Under these conditions, no layer‐specific distribution of astrocytic GS immunoreactivity could be demonstrated. This suggests that the laminated distribution of GS immunoreactivity is formed in parallel with the segregated termination of hippocampal afferents. Thus, there is no predetermined pattern of GS‐containing astrocytes playing a role in the segregation of extrinsic fibres. The ultrastructural localization of GS immunoreactivity in fine astrocytic processes around asymmetric, probably glutamatergic excitatory spine synapses confirms earlier in situ findings, which suggests that this arrangement is a global phenomenon of glutamatergic systems.
Differential Visualization of Dopamine D2 and D3 Receptor Sites in Rat Brain. A Comparative Study Using In Situ Hybridization Histochemistry and Ligand Binding Autoradiography
Authors: Landwehrmeyer B. , Mengod G. , Palacios J. M. 
Published: April 2006

AbstractAt least five members of the dopamine receptor family have been characterized at the gene level. D2, D3 and D4 dopamine receptors are related pharmacologically. In order to visualize the differential expression of D1, D2 and D3 receptors in rat brain we have combined in situ hybridization histochemistry with receptor autoradiography. Regions enriched with D3 messenger RNA (mRNA) included the islands of Calleja (ioC) and nucleus accumbens. Very low or undetectable levels were present in the caudate–putamen. In contrast, no D2 transcripts were observed in the islands of Calleja, but there were high levels in the nucleus accumbens, caudate–putamen (CP) and pyramidal layer of the olfactory tubercle. A comparison of the binding pattern of six dopamine receptor radioligands hitherto regarded as D2 receptor‐selective showed that the islands of Calleja were intensely labelled by [125I]iodosulpride, [3H]CV 205 502 and [3H]SDZ 205 501, while the binding of [3H]spiperone, [3H]raclopride and [3H]YM 09151–2 was much lower or undetectable. Pharmacological analysis of the binding of D2/D3 ligands to the islands of Calleja and caudate–putamen suggests that binding sites in these two regions are of different pharmacology, consistent with the presence of D3 sites in the islands of Calleja and the predominance of D2 sites in the caudate. These results demonstrate the expression of D3 binding sites in the rat brain and provide a procedure to differentiate D2 and D3 receptor populations in binding studies.