bluuebunny/crossref_metadata_2025_split huggingface dataset:
SHORT COMUNICATIONEarly sodium elevations induced by combined oxygen and glucose deprivation in pyramidal cortical neurons
Authors: Pisani Antonio , Calabresi Paolo , Tozzi Alessandro , Bernardi Giorgio , Knöpfel Thomas 
Published: March 2003

AbstractWe investigated the effects of oxygen (O2)/glucose deprivation on intracellular sodium concentration ([Na+]i) of cortical pyramidal cells in a slice preparation of rat frontal cortex. Intracellular recordings were combined with microfluorometric measurements of [Na+]i using the Na+‐sensitive dye sodium‐binding benzofuran isophthalate (SBFI). Deprivation of O2/glucose caused an initial membrane hyperpolarization that was followed by a slowly developing large depolarization. Levels of [Na+]i started to increase significantly during the phase of membrane hyperpolarization. Neither tetrodotoxin, a combination of ionotropic and metabotropic glutamate receptor antagonists (d‐amino‐phosphonovalerate, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione plus S‐methyl‐4‐carboxyphenylglycine) nor bepridil, an inhibitor of the Na+/Ca2+‐exchanger, affected these responses to O2/glucose. The present results demonstrate that, in cortical neurons, O2/glucose deprivation induces an early rise in [Na+]i which cannot be ascribed to the activity of voltage gated Na+‐channels, glutamate receptors or of the Na+/Ca2+‐exchanger.
Shaping of the cat paw for food taking and object manipulation: an X‐ray analysis
Authors: Boczek‐Funcke A. , Kuhtz‐Buschbeck J. P. , Raethjen J. , Paschmeyer B. , Illert M. 
Published: March 2003

AbstractThe kinematics of the cat distal forelimb during food‐taking were analysed to obtain information on the movement processes within the paw before and during object taking in a species without monosynaptic cortico‐motoneuronal projections. The behaviour was investigated with two tests: either the table test (TT, food offered on a table located at ground level in a reaching distance of 22 and 28 cm) or the horizontal test (HT, food offered in a small container located at shoulder level, height 18–25 cm, reaching distance 6–12 cm). In five animals, the changes in configuration and the conjoint actions of the wrist, the metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joints were assessed with three‐dimensional X‐ray cinematography (time resolution 20 ms, spatial resolution 1 mm) and video analysis.While approaching the target, the digits were first extended and subsequently abducted. This ‘preshaping’ consisted of combined angular changes in the MCP and PIP joints, thereby attaining an adequate grip aperture. Each cat used a stable strategy, but different cats used different strategies. In the TT, preshaping involved an MCP extension and a PIP flexion. In the HT, predominant extension of the MCP, predominant extension of the PIP, or a combination of both were used, followed by MCP flexion and PIP flexion. The grip aperture started to decrease before object contact, earlier in the TT, later in the HT. Grasping was achieved by flexion of first the PIP and later the MCP.The X‐ray analysis gave evidence for individuated digit movements. Correlation analysis of the angular position of the joints between the different phalanges showed that digits 3 and 4 acted in concert, as did digits 2 and 5, but with clear independence between the different pairs. Furthermore, the different phalanges served different purposes during the grasp. Digits 3, 4 established object contact, digits 2, 5 were mainly used to stabilize the paw onto the surface.The cat distal forelimb displays a refined movement repertoire during the preshaping and grasping phase of food‐taking. During the preshaping phase, the kinematics resembled in some aspects the situation in humans. The results demonstrate the ability of the polysynaptic projections from the cortico‐motoneuronal system to organize differentiated distal limb movements, including individuated movements of the digits.
Acute inactivation of the inferior olive blocks associative learning
Authors: Welsh John P. , Harvey John A. 
Published: March 2003

AbstractCan acute inactivation of the inferior olive block associative learning? We anaesthetized the inferior olive with lidocaine while rabbits simultaneously: (i) performed conditioned nictitating membrane responses to a flashing light to which they had already been trained; and (ii) underwent their first experience with classical conditioning of the same response to a tone. Inactivation of the inferior olive immediately and reversibly abolished the performance of conditioned responses and prevented learning during rabbits' initial conditioning with a tone‐conditioned stimulus. When olivary function was restored, rabbits showed no signs of having learned under olivary anaesthesia. The experiment demonstrates that an acute disruption in olivary function can block learning, in addition to severely degrading motor control. The results are interpreted to indicate the importance of the inferior olive in optimizing learning, perhaps through a general role in regulating temporal processing.
Stratum radiatum giant cells: a type of principal cell in the rat hippocampus
Authors: Gulyás A. I. , Tóth K. , McBain C. J. , Freund T. F. 
Published: March 2003

AbstractNeurons of a distinct type in CA1 area stratum radiatum of the rat hippocampus have been found to express a direct cellular form of long‐term potentiation (LTP, Maccaferri & McBain, 1996, J. Neurosci.16, 5334), but their functional identity, i.e. whether interneuron or principal cell, remained unknown. Whole cell recording from hippocampal slices in vitro was combined with light and electron microscopy to answer this question. LTP was robustly induced by a pairing protocol and physiological properties were measured in radiatum giant cells (RGCs) using biocytin containing pipettes. Reconstruction of the cells' dendritic and axonal arbor revealed morphological properties similar to CA1 pyramidal cells with some characteristic differences. They typically had two large diameter apical dendrites, or when only one dendrite arose, it soon bifurcated. Apical dendrites formed a dendritic tuft in stratum lacunosum‐moleculare and the dendrites, but not the somata, were densely covered with conventional spines. The axon arose from the basal pole of the soma, descended to stratum oriens and emitted several axon terminals bearing collaterals that travelled horizontally, remaining in stratum oriens. The main, myelinated axon trunks turned towards the fimbria. In the electron microscope axon terminals were found to form asymmetrical synapses on postsynaptic dendritic shafts and dendritic spines in stratum oriens. The dendrites received asymmetrical synapses, mostly on their spines. The axon initial segments also received several synapses, a feature never observed on interneurons. All the above characteristics support the conclusion that RGCs are excitatory principal neurons.
European Neuroscience Association The changing pattern of fibre bundles that pass through the optic chiasm of mice
Authors: Colello S. J. , Guillery R. W. 
Published: March 2003

AbstractThe organization of retinofugal fibres in the developing and adult mouse has been studied with transmission electron microscopy, autoradiography and the Bodian silver method. It has previously been shown that all retinal ganglion cell axons are in glial‐wrapped bundles in the developing and adult optic nerve, but are not in similar bundles close to the chiasm. In the embryonic mouse this region shows a transition in glial morphology from an interfascicular to a radial type and here retinofugal fibres begin to form a new order related to their age. Growth cones become concentrated at the pial surface of the juxtachiasmatic nerve and older fibres are restricted to deeper regions. This same age‐related order is also evident in the optic tract. However, the age‐related order is lost within the chiasm, where growth cones, young and old fibres are again mingled in distinct bundles as they cross the mid‐line. This study is particularly concerned with the structure of the mid‐line bundles. These fibre bundles cross each other at right angles, and are recognizable in fetal and adult mice. In the adult, monocular injections of H3 proline followed by autoradiographic study show that the individual mid‐line bundles are monocular and that they fuse again, losing the fascicular structure as they leave the chiasm and enter the tract. In the fetus and in the adult, the bundles generally lack a complete glial wrapping so that growth cones can lie in intimate contact with two crossing bundles, one coming from the left eye, the other from the right. The interesting question about the mechanisms that keep growth cones from entering the wrong bundles when they are in this position remains to be addressed.
A purinergic component of the excitatory postsynaptic current mediated by P2X receptors in the CA1 neurons of the rat hippocampus
Authors: Pankratov Yuri , Castro Enrique , Miras‐Portugal Maria Teresa , Krishtal Oleg 
Published: March 2003

AbstractThe pyramidal neurons in the CA1 area of hippocampal slices from 17‐ to 19‐day‐old rats have been investigated by means of patch clamp. Excitatory postsynaptic currents (EPSCs) were elicited by stimulating the Schaffer collateral at a frequency below 0.2 Hz. It was found that inhibition of glutamatergic transmission by 20 μm 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) and 100 μm 2‐amino‐5‐phosphonovaleric acid (D‐APV) left a small component of the EPSC uninhibited. The amplitude of this residual EPSC (rEPSC) comprised 25 ± 11% of the total EPSC when measured at a holding potential of −50 mV. The rEPSC was blocked by selective P2 blocker pyridoxal phosphate‐6‐azophenyl‐2′‐4′‐disulphonic acid (PPADS) 10 μm and bath incubation with non‐hydrolysable ATP analogues, ATP‐γ‐S and α,β‐methylene‐ATP at 50 and 20 μm, respectively. The rEPSC was dramatically potentiated by external Zn2+ (10 μm). In another series of experiments exogenous ATP was applied to the CA1 neurons in situ. An inward current evoked by ATP was inhibited by PPADS to the same extent as the rEPSC. It is concluded that, depending on membrane voltage, about one‐fifth to one‐quarter of the EPSC generated by the excitatory synaptic input to the hippocampal CA1 neurons of rat is due to the activity of P2X receptors.
Hippocampal synaptic density and glutamate immunoreactivity following transient cerebral ischaemia in the chick
Authors: Horner Catherine H. , Davies Heather A. , Stewart Michael G. 
Published: March 2003

AbstractA transient ischaemic episode of 10 min duration was induced in 1‐day‐old chicks. After a 1‐week survival period, synapse density was assessed in the ventral hippocampus using the ‘disector’ technique. A significant decrease was observed in asymmetric synapses, markedly greater than that observed previously in the dorsal hippocampus. Because the effect occurred mainly on excitatory synapses, the distribution of glutamate in the ventral hippocampus was also assessed by a postembedding immunogold labelling technique. The density of gold particles was significantly greater in both boutons and neuropil in the ischaemic group compared to controls, lending support to the theory of excitotoxicity as an explanation for ischaemic neural degeneration.
Individual differences in stress‐induced dopamine release in the nucleus accumbens are influenced by corticosterone
Authors: Rougé‐Pont Françoise , Deroche Véronique , Moal Michel Le , Piazza Pier Vincenzo 
Published: March 2003

AbstractStressful experiences, glucocorticoids hormones and dopaminergic neurons seems to interact in determining a higher propensity to develop drug abuse. In this report, we studied the acute interaction between these three factors. For this purpose, we compared stress‐induced dopamine release in intact rats and in rats in which stress‐induced corticosterone secretion was experimentally blocked. Ten‐minute tail‐pinch was used as a stressor and dopamine release estimated in the nucleus accumbens by using the microdialysis technique. Individual differences were also taken into account by comparing rats identified as either predisposed (HRs) or resistant (LRs) to develop self‐administration of drugs of abuse, on the basis of their locomotor response to novelty. It was found that suppression of stress‐induced corticosterone secretion significantly decreased stress‐induced dopamine release. However, such an effect greatly differed between HR and LR rats. When corticosterone secretion was intact HR animals had a higher and longer dopamine release in response to stress than LRs. The blockade of stress‐induced corticosterone secretion selectively reduced the dopaminergic response of HRs that did not differ from LRs anymore. These findings strength the idea that glucocorticoids could be involved in determining propensity to develop drug self‐administration. In particular, these hormones could play a role in determining the higher dopaminergic activity that characterizes drug proned individuals.
Functional Expression Of GFP‐Tagged Kv1.3 And Kv1.4 Channels In HEK 293 Cells
Authors: Jürgen Kupper 
Published: March 2003

AbstractVarious types of voltage gated potassium channels (Kv) are responsible for setting the resting potential and shaping the membrane potential waveform in the subcellular domains of neurons. In order to visualize the expression behaviour of recombinant Kv channels, we have fused green fluorescent protein (GFP) to the N‐terminal of the α subunits Kv1.3 and Kv1.4. In transiently transfected HEK 293 cells the GFP‐Kv chimeras localize to the plasma membrane. Whole‐cell voltage clamp recordings demonstrate that they form functional potassium channels. Kinetic analysis reveals that the gating kinetics of GFP‐Kv1.3 are virtually indistinguishable from those displayed by its wild‐type correlate. For GFP‐Kv1.4 channels we find that their gating is modified in an expected manner. In response to short depolarizing voltage pulses they do not inactivate, indicating that the attached GFP interferes with the fast N‐type inactivation mechanism present in wild type Kv1.4 channels. We suggest that GFP tagging of Kv channels might be a useful tool to monitor the spatiotemporal distribution of recombinant potassium channels expressed in living neurons.
How does the human brain deal with a spinal cord injury?
Authors: Bruehlmeier M. , Dietz V. , Leenders K. L. , Roelcke U. , Missimer J. , Curt A. 
Published: March 2003

AbstractThe primary sensorimotor cortex of the adult brain is capable of significant reorganization of topographic maps after deafferentation and de‐efferentation. Here we show that patients with spinal cord injury exhibit extensive changes in the activation of cortical and subcortical brain areas during hand movements, irrespective of normal (paraplegic) or impaired (tetraplegic patients) hand function. Positron emission tomography ([15O]‐H2O‐PET) revealed not only an expansion of the cortical ‘hand area’ towards the cortical ‘leg area’, but also an enhanced bilateral activation of the thalamus and cerebellum. The areas of the brain which were activated were qualitatively the same in both paraplegic and tetraplegic patients, but differed quantitatively as a function of the level of their spinal cord injury. We postulate that the changes in brain activation following spinal cord injury may reflect an adaptation of hand movement to a new body reference scheme secondary to a reduced and altered spino‐thalamic and spino‐cerebellar input.
Prolonged expression of zinc finger immediate‐early gene mRNAs and decreased protein synthesis following kainic acid induced seizures
Authors: Honkaniemi Jari , Sharp Frank R. 
Published: March 2003

AbstractIn the present study in situ hybridization was used to study the effect of kainic acid induced seizures on the expression of the zinc finger immediate‐early genes (IEGs) NGFI‐A, NGFI‐B, NGFI‐C, egr‐2, egr‐3 and Nurr1. Kainic acid markedly induced these IEGs especially in hippocampus, cortex and amygdala by 30 min. This induction gradually decreased and returned to baseline by 24 h in most regions. However, in the CA1 and CA3 subfields of hippocampus known to be damaged by kainic acid the expression of all the IEGs except egr‐2 remained elevated for 24 h. NGFI‐A, NGFI‐B, NGFI‐C and to a lesser extent, Nurr1, remained elevated also in the subcortical region of the temporal lobe. By 24 h incorporation of 14C‐leucine decreased in the piriform cortex, amygdala, and in the CA1 and CA3 subfields, but not in CA2 and dentate gyrus. These areas showing decreased protein synthesis in the hippocampus by 24 h showed prolonged IEG induction, whereas IEG expression returned to control levels in areas showing normal protein synthesis. In the temporal lobe decreased protein synthesis coexisted with decreased IEG expression, whereas areas in the vicinity of the region showing decreased protein synthesis demonstrated elevated IEG expression. The decreased protein synthesis was localized in areas where extensive neuronal death has occurred. This prolonged IEG induction in the hippocampus, which has been linked with neuronal death, could solely represent a prolonged mRNA turnover caused by disrupted protein synthesis. The prolonged IEG expression in the temporal lobe appeared to be localized in regions where the cells are in stress, but still viable. The sustained IEG expression might therefore either represent a stress response by which the neurons are trying to protect themselves or, alternatively, the IEG response may be an early sign indicating that these cells are initiating a pathway leading to programmed cell death.
Nicotinic receptors in the rat prefrontal cortex: increase in glutamate release and facilitation of mediodorsal thalamo‐cortical transmission
Authors: Gioanni Y. , Rougeot C. , Clarke P. B. S. , Lepousé C. , Thierry A. M. , Vidal C. 
Published: March 2003

AbstractThe modulatory influence of nicotinic acetylcholine receptor (nAChRs) on thalamocortical transmission was characterized in the prelimbic area (PrL) of the rat prefrontal cortex. In the first experiment, rats received a unilateral excitotoxic lesion centred on the mediodorsal thalamic nucleus (MD), and were sacrificed 1 week later. The lesion resulted in a 40% reduction of 3H‐nicotine autoradiographic labelling in the ipsilateral prefrontal cortex, particularly in areas that are innervated by the MD. Electrophysiological experiments were subsequently performed in non‐lesioned anaesthetized animals, in order to study modulation of short‐ and long‐latency responses of PrL neurons evoked by electrical stimulation of the MD. The short‐latency responses result from activation of the MD–PrL pathway and are mediated via AMPA‐type glutamatergic receptors, whereas the long‐latency responses reflect activation of the recurrent collaterals of cortical pyramidal neurons. Iontophoretic application of nicotinic agonists (nicotine, DMPP) facilitated both types of response. Local application of the nAChR antagonists dihydro‐beta‐erythroidine, mecamylamine and methyllycaconitine, prevented both kinds of facilitation. Finally, intracerebral microdialysis experiments were performed in order to test for nicotinic modulation of extracellular glutamate concentrations in the PrL. Direct application of nicotine via the dialysis probe increased glutamate levels in a dose‐dependent manner. This effect was blocked by local perfusion of dihydro‐beta‐erythroidine. These findings therefore provide anatomical and functional evidence for nAChR‐mediated modulation of thalamocortical input to the prefrontal cortex. Such a mechanism may be relevant to the cognitive effects of nicotine and nicotinic antagonists.
Stimulus‐function, wind‐up and modulation by diffuse noxious inhibitory controls of responses of convergent neurons of the spinal trigeminal nucleus oralis
Authors: Dallel Radhouane , Duale Christian , Luccarini Philippe , Molat Jean‐Louis 
Published: March 2003

AbstractExtracellular unitary recordings were made from 53 spinal trigeminal nucleus oralis (Sp5O) convergent neurons in halothane‐anaesthetized rats. The neurons had an ipsilateral receptive field including mainly oral or perioral regions. They responded to percutaneous electrical stimulation with two peaks of activation. The first had a short latency (4.3 ± 0.3 ms) and low threshold (0.35 ± 0.04 mA), whereas the second had a longer latency (68.1 ± 3.4 ms) and higher threshold (7.3 ± 0.5 mA). Intracutaneous injection of capsaicin (0.1%) produced a strong and rapid reduction of the long‐latency responses of Sp5O convergent neurons with little effect on the short‐latency responses. In most cases (73%), the long‐latency responses exhibited a wind‐up phenomenon during repetitive (0.66 Hz) suprathreshold electrical stimulation. These results suggest that C‐fibres mediate the long‐latency response of Sp5O convergent neurons. Regarding the C‐fibre‐evoked responses, a linear relationship between the intensity of the applied current and the magnitude of the response was found within the one to three times threshold range. The Sp5O convergent neurons also encoded the intensity of mechanical stimuli applied to the skin or mucosa in the 5–50 g ranges. The evoked activity of Sp5O convergent neurons could be suppressed by noxious heat applied to the tail (52 °C) and long‐lasting poststimulus effects followed this. These findings show that convergent neurons in the Sp5O resemble those in the deep laminae of the spinal dorsal horn and spinal trigeminal nucleus caudalis, and further support that the Sp5O plays a part in the processing of nociceptive information from the orofacial region.
Enhanced synaptic transmission and reduced threshold for LTP induction in fyn‐transgenic mice
Authors: Lu Y. ‐F. , Kojima N. , Tomizawa K. , Moriwaki A. , Matsushita M. , Obata K. , Matsui H. 
Published: March 2003

AbstractTo elucidate the physiological role of Fyn, we analysed the properties of synaptic transmission and synaptic plasticity in hippocampal slices of mice overexpressing either wild‐type Fyn (w‐Fyn) or its constitutively active mutant (m‐Fyn). These fyn‐transgenes were driven by the calcium/calmodulin‐dependent protein kinase IIα promoter which turned on in the forebrain neurons including hippocampal pyramidal cells and in late neural development. In the hippocampal slices expressing m‐Fyn the paired‐pulse facilitation was reduced and the basal synaptic transmission was enhanced. A weak theta‐burst stimulation, which was subthreshold for the induction of long‐term potentiation (LTP) in control slices, elicited LTP in CA1 region of the slices expressing m‐Fyn. When a relatively strong stimulation was applied, the magnitude of LTP in m‐Fyn slices was similar to that in control slices. By contrast, the basal synaptic transmission and the threshold for the induction of LTP were not altered in the slices overexpressing wild‐type Fyn. To examine the effect of expression of m‐Fyn on GABAergic inhibitory system, we applied bicuculline, a GABAA receptor blocker, to the hippocampal slices. The ability of bicuculline to enhance excitatory postsynaptic potentials was attenuated in slices expressing m‐Fyn, suggesting that the overexpression of m‐Fyn reduced the GABAergic inhibition. The enhancement of synaptic transmission and the reduction of GABAergic inhibition may contribute to the enhanced seizure susceptibility in the mice expressing m‐Fyn. Thus, these results suggest that regulation of Fyn tyrosine kinase activity is important for both synaptic transmission and plasticity.