bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nerve growth factor (NGF) induces motoneuron apoptosis in rat embryonic spinal cord in vitro
Authors: Sedel Frédéric , Béchade Catherine , Triller Antoine 
Published: March 2003

AbstractRecent studies have demonstrated that nerve growth factor (NGF) induces apoptosis of several cell types in the central nervous system through its low‐affinity p75 neurotrophin receptor (p75NTR). To test the effect of NGF on embryonic motoneuron survival, we developed an organotypic culture system which allowed the in vitro development of intact embryonic rat spinal cords. In our system, neural tubes were taken and cultured at E13, just before the onset of physiological motoneuron death. After 2 days in vitro (DIV), motoneurons underwent apoptosis over a time‐course similar to that in vivo. In this system, the addition of NGF (200 ng/mL) for 2 days enhanced the number of apoptotic motoneurons by 37%. This pro‐apoptotic effect was completely reversed by the blocking anti‐p75NTR (REX) antibody which inhibits NGF binding to p75NTR. Other neurotrophins, e.g. brain‐derived neurotrophic factor (BDNF), neurotrophin 3 (NT3) and neurotrophin 4/5 (NT4/5) did not have any effect, while glial cell‐derived neurotrophic factor (GDNF) promoted motoneuron survival. Anti‐BDNF blocking antibodies enhanced motoneuron death indicating that endogenous BDNF promotes motoneuron survival in explants. Our results demonstrate, for the first time, that NGF can induce embryonic motoneuron apoptosis through its receptor p75NTR.
Vasopressin in the lateral septum promotes elemental conditioning to the detriment of contextual fear conditioning in mice
Authors: Desmedt Aline , Garcia René , Jaffard Robert 
Published: March 2003

AbstractPrevious experiments using a classical fear conditioning paradigm have provided evidence that the processing of contextual conditional stimuli (CSs) by the hippocampus would be controlled by the amygdala through a modulation of hippocampal‐lateral septal (H‐LS) excitability. More specifically, our suggestion was that vasopressin release into the LS would occur in an elemental conditioning case [pairing CS–US (unconditional stimulus) procedure] and would result in less hippocampal‐dependent contextual stimuli processing (i.e. overshadowing of CSs by the simple CS). Conversely, when an unpairing CS–US procedure is used, this would result in more contextual stimuli processing through a decrease in vasopressin release into the LS. The aim of the present experiment was to test this hypothesis using intraseptal injection of vasopressin or its V1/V2 antagonist. In agreement with this hypothesis, results suggest that vasopressin release into the LS would constitute a device by which priority is given to the more salient simple stimulus to the detriment of contextual information.
The neurosteroid pregnenolone sulphate increases dopamine release and the dopaminergic response to morphine in the rat nucleus accumbens
Authors: Barrot Michel , Vallée Monique , Gingras Mireille A. , Le Moal Michel , Mayo Willy , Piazza Pier Vincenzo 
Published: March 2003

AbstractNeurosteroids are a subclass of steroids that can be synthesized in the central nervous system independently of peripheral sources. Clinical studies in humans have associated some of these hormones with a generic sensation of ‘well‐being’ and with pathologies such as depression. In rodents, the neurosteroid pregnenolone sulphate (Preg‐S) has been shown to present antidepressant‐like effects. These observations suggest that neurosteroids could interact with reward‐related processes, mood and motivation. However, the possible neural substrates of such an effect remain unclear. In this report, we studied the action of Preg‐S on the activity of the mesencephalic dopaminergic projection to the nucleus accumbens which is considered one of the biological substrates of motivation and reward. Both the direct effect of Preg‐S and the influence of this hormone on the dopaminergic response to the pharmacological reward provided by the opiate morphine, were studied by means of microdialysis. Pregnenolone sulphate dose‐dependently increased dopamine release in the nucleus accumbens. Furthermore, this hormone doubled the dopaminergic response to morphine. These effects were observed for Preg‐S doses of 100, 200, and 400 pmol injected intracerebroventricularly. The stimulant effect of Preg‐S on dopamine could mediate some of the behavioural effects of neurosteroids and in particular the interaction of these hormones with mood and motivation.
The cortical visual area V6: brain location and visual topography
Authors: Galletti Claudio , Fattori Patrizia , Gamberini Michela , Kutz Dieter F. 
Published: March 2003

AbstractThe brain location and topographical organization of the cortical visual area V6 was studied in five hemispheres of four awake macaque monkeys. Area V6 is located in the caudal aspect of the superior parietal lobule (SPL). It occupies a ‘C’‐shaped belt of cortex whose upper branch is in the depth of the parieto‐occipital sulcus (POS) and lower one is in the depth of the medial parieto‐occipital sulcus (POM), with the medial surface of the brain as a zone of junction between the two branches. Area V6 contains a topographically organized representation of the contralateral visual field up to an eccentricity of at least 80 °. The lower visual field representation is located dorsally, in the ventral part of POS, and the upper field ventrally, in the dorsal wall of POM. The representation of the horizontal meridian forms the posterior border of V6. It is adjacent to area V3 in POS as well as in the caudal part of POM, on the ventral convexity of the brain. The lower vertical meridian forms the anterior border of V6, adjacent to area V6A. The upper vertical meridian is in the depth of POM. The representation of the central visual field is not magnified relative to that of the periphery. The central visual field (below 20–30 ° of eccentricity) is represented in the medial‐most aspect of the annectant gyrus, in the lateral part of the posterior bank of POS. The visuotopic organization of area V6 suggests a role in the analysis of the flow field resulting from self‐motion, in selecting targets during visual searching as well as in the control of arm‐reaching movements towards non‐foveated targets.
The paleocortical ventricle is the origin of reelin‐expressing neurons in the marginal zone of the foetal human neocortex
Authors: Meyer Gundela , Wahle Petra 
Published: March 2003

AbstractThe subpial granular layer (SGL) is a transient cell layer in the cortical marginal zone during the period of neuronal migration into the cortical plate. The origin of the SGL has been studied by immunocytochemistry for calretinin (CR) and reelin in human foetuses from 11 to 40 gestational weeks (GW). At 11 GW, the paleocortical ventricle, a rostral dilatation of the lateral ventricle, gives rise to two fountainheads: a medial fountainhead provides neurons for the marginal zone (MZ) of the rostral cortex and rostral hippocampal rudiment, while multiple cell streams migrate from a lateral fountainhead into the MZ of the paleocortex and insula. The latero‐medial gradient of neuronal packing density in the neocortical MZ indicates that migration extends farther into the neocortex. Neurons express CR already in the retrobulbar ventricular zone; they express reelin only as they approach the MZ of the paleocortex and rostral archicortex. At 16/17 GW, large numbers of CR‐immunoreactive granule cells originate from the same fountainheads, and then direct medially, toward the surface of the anterior perforated substance, and laterally, into the paleocortical MZ, from where they continue into the neocortical SGL following a ventrolateral to dorsomedial gradient. From 13 to 18 GW, reelin is expressed by a subpopulation of granule cells and by Cajal–Retzius‐like neurons. By 22 GW, the paleocortical ventricle undergoes regression and no longer supplies the SGL. Our results show that the paleocortical ventricle gives rise to a stream of neurons which extends over the cortical MZ as the subpial granular layer. The fact that SGL derivatives express reelin suggests that this transient cell layer may play a significant role in the establishment of the complex cytoarchitecture of the cerebral cortex.
Prior short‐term synaptic disinhibition facilitates long‐term potentiation and suppresses long‐term depression at CA1 hippocampal synapses
Authors: Hsu Kuei‐Sen , Ho Wen‐Chia , Huang Chiung‐Chun , Tsai Jing‐Jane 
Published: March 2003

AbstractLong‐term potentiation (LTP) and long‐term depression (LTD) are two main forms of activity‐dependent synaptic plasticity that have been extensively studied as the putative mechanisms underlying learning and memory. Current studies have demonstrated that prior synaptic activity can influence the subsequent induction of LTP and LTD at Schaffer collateral‐CA1 synapses. Here, we show that prior short‐term synaptic disinhibition induced by type A γ‐aminobutyric acid (GABA) receptor antagonist picrotoxin exhibited a facilitation of LTP induction and an inhibition of LTD induction. This effect lasted between 10 and 30 min after washout of picrotoxin and was specifically inhibited by the L‐type voltage‐operated Ca2+ channel (VOCC) blocker nimodipine, but not by the N‐methyl‐d‐aspartate (NMDA) receptor antagonist d‐2‐amino‐5‐phosphopentanoic acid (D‐APV). Moreover, this picrotoxin‐induced priming effect was mimicked by forskolin, an activator of cyclic adenosine monophosphate (cAMP)‐dependent protein kinase (PKA), and was blocked by the adenylyl cyclase inhibitor 9‐(tetrahydro‐2‐furanyl)‐9H‐purin‐6‐amine (SQ 22536) and the PKA inhibitor Rp‐adenosine 3′,5′‐cyclic monophosphothioate (Rp‐cAMPS). It was also found that following picrotoxin application, CA1 neurons have a higher probability of synchronous discharge in response to a population of excitatory postsynaptic potential (EPSP) of fixed slope (EPSP/spike potentiation). However, picrotoxin treatment did not significantly affect paired‐pulse facilitation (PPF). These findings suggest that a brief of GABAergic disinhibition can act as a priming stimulus for the subsequent induction of LTP and LTD at Schaffer collateral‐CA1 synapses. The increase in Ca2+ influx through L‐type VOCCs in turn triggering a cAMP/PKA signalling pathway is a possible molecular mechanism underlying this priming effect.
Abnormal expression of neurofilament proteins in dysmyelinating axons located in the central nervous system of jimpy mutant mice
Authors: Gotow Takahiro , Leterrier Jean F. , Ohsawa Yoshiyuki , Watanabe Tsuyoshi , Isahara Kyoko , Shibata Riichi , Ikenaka Kazuhiro , Uchiyama Yasuo 
Published: March 2003

AbstractMyelination in the peripheral nervous system is considered to increase the phosphorylation level of neurofilament proteins in the axon, resulting in an increase in axonal calibre. To understand the relationship between myelination and neurofilament proteins in axons, we examined jimpy mutant mice with a point mutation in the proteolipid protein gene and dysmyelination in the central nervous system. The jimpy mice exhibited a characteristic similarity in neurofilament nature to the myelin‐deficient mice in the peripheral nervous system reported previously. The following novel results were obtained in the jimpy mice: dysmyelinated axons, in which the amount of non‐phosphorylated neurofilament‐H was drastically increased without a significant reduction of the phosphorylated form, compared with the control myelinated axons, did not suffer any decrease in their diameters. Expression levels of all neurofilament subunit proteins and their mRNAs were enhanced in the central nervous system tissue. Because the above biochemical data were obtained from the cytoskeletal fraction, at least some of the increased neurofilament‐H and ‐M proteins appeared to be coassembled into neurofilaments but remained non‐phosphorylated. Axonal neurofilaments of the jimpy were, probably due to this abnormal stoichiometry and phosphorylation state in neurofilaments, more compact and random in alignment with less prominent cross‐bridges than those of the control, providing possible evidence for disturbing the axonal transport of other organelles. These results suggest that myelination regulates both the expression and phosphorylation of neurofilament proteins, and is essential for the cytoplasmic organization of myelinated axons.
Improved auditory spatial acuity in visually deprived ferrets
Authors: King Andrew J. , Parsons Carl H. 
Published: March 2003

AbstractWe have examined the effects on auditory spatial acuity in the horizontal plane of depriving ferrets of patterned visual cues by binocular eyelid suture in infancy or for a comparable period in adulthood. Minimum audible angles (MAAs) were measured for 500‐, 100‐ and 40‐ms broadband noise bursts at the midline and at 45° to one side. A logistic regression analysis revealed no consistent difference between the midline MAAs of normal and infant lid‐sutured ferrets. However, the lateral field MAAs of the infant‐deprived group were significantly smaller and showed less inter‐subject variability than those of normal‐sighted ferrets. The animals deprived in adulthood were tested in the lateral field only, firstly 6 months after binocular eyelid suture and again after a further 10 months. For the first test, the MAAs achieved by these animals with 500‐ and 100‐ms noise bursts were significantly smaller than the normal values and no different from those of the infant‐deprived group. A significant improvement in performance at the two shortest stimulus durations (100 and 40 ms) was observed when the adult‐deprived animals were re‐tested. Their second‐test MAAs did not differ from those of the infant‐deprived group at any of the three stimulus durations used, and both groups achieved significantly better scores than the normal‐sighted control animals. These results show that prolonged visual deprivation in both juvenile and adult ferrets can lead to a significant improvement in auditory spatial acuity in the lateral sound field. This is consistent with reports that congenitally blind humans can localize peripheral sounds more accurately than normal controls.
Postnatal loss of Merkel cells, but not of slowly adapting mechanoreceptors in mice lacking the neurotrophin receptor p75
Authors: Kinkelin Ilka , Stucky Cheryl L. , Koltzenburg Martin 
Published: March 2003

AbstractMerkel cells are specialized epidermal cells which are abundantly found in touch‐sensitive areas and which are innervated by slowly adapting mechanosensitive afferent fibres with large myelinated (Aβ) axons. The role of Merkel cells in mechanosensation, their developmental regulation and their influence on sensory neuron function are, however, incompletely understood. Here, we used mice lacking the neurotrophin receptor p75 which is expressed on Merkel cells to investigate their postnatal development and that of their innervating sensory neurons. Using morphological studies we now show that Merkel cells develop normally in both hairy and glabrous skin in these animals until 2 weeks old, but are progressively lost thereafter and have almost completely disappeared 2 months after birth. Using standard extracellular electrophysiological recording techniques we find that despite the profound loss of Merkel cells there is no corresponding reduction in the number of myelinated slowly adapting afferent fibres. Moreover, the mean mechanical threshold of these neurons and their average stimulus response function to suprathreshold mechanical stimuli does not change during the time period when more than 99% of Merkel cells are lost. We conclude that Merkel cells require p75 during the late postnatal development. However, neither the survival nor the mechanical sensitivity of slowly adapting mechanoreceptive Aβ‐fibres depends on the presence of Merkel cells.
Stimulation of nicotinic receptors in the lateral septal nucleus increases anxiety
Authors: Ouagazzal Abdel‐Mouttalib , Kenny Paul J. , File Sandra E. 
Published: March 2003

AbstractThe present study investigated the role of nicotinic receptors in the lateral septum in the modulation of anxiety. The effects of direct injections of nicotine into the lateral septum were first investigated in two tests of anxiety, social interaction and elevated plus‐maze tests. Intra‐septal injection of nicotine (1 and 4 μg) induced consistent anxiogenic effects in both tests. The reversal of nicotinic effects with mecamylamine was then studied in the social interaction test. Intra‐septal injection of mecamylamine at a low dose (15 ng) induced an anxiolytic effect, suggesting the presence of intrinsic cholinergic tone increasing anxiety. At higher doses (30–50 ng), mecamylamine was without effect in the social interaction test, but blocked the anxiogenic effects of nicotine (4 μg). These findings provide further evidence for the role of the lateral septum in the modulation of anxiety and suggest that cholinergic projections to this brain area facilitate anxiety through nicotinic receptors.
Neuroactive steroids and the constraint of memory
Authors: Slot L. A. Bruins , Piazza P. V. , Colpaert F. C. 
Published: March 2003

AbstractDifferent normo‐ and pathophysiological conditions are associated with large variations in plasma and brain concentrations of neuroactive steroids. In an attempt to specify the possible role of these steroids in memory processes, we examined the ability of pregnanolone, a positive modulator of the γ‐aminobutyric acid type A (GABAA) receptor complex, to sustain state dependence in rats. Animals treated with either saline or different doses of pregnanolone were trained to complete a fixed ratio 10 (FR10) schedule of lever presses for milk reward within 120 s, and were tested for the retention of this response 48 h later while treated with the same or a different treatment. The data indicate that saline‐to‐drug as well as drug‐to‐saline state changes produced robust failures to recall the response. Furthermore, animals trained with pregnanolone showed transfer of the response when tested with the benzodiazepine chlordiazepoxide and vice versa. The partial benzodiazepine inverse agonist N‐methyl‐β‐carboline‐3‐carboxamide (FG‐7142) antagonized the states produced by both pregnanolone and chlordiazepoxide. State changes constitute a mechanism of action that may operate endogenously; the release of neuroactive steroids in response to various physiological conditions may act to contain but also to constrain memories associated with these events, rendering these memories inaccessible on other occasions. The apparent memory impairment that can so be produced may render the effects of past experience available in a manner that is appropriately selective.
The cerebellum and cognition: cerebellar lesions do not impair spatial working memory or visual associative learning in monkeys
Authors: Nixon Philip D. , Passingham Richard E. 
Published: March 2003

AbstractAnatomical studies in non‐human primates have shown that the cerebellum has prominent connections with the dorsal, but not the ventral, visual pathways of the cerebral cortex. Recently, it has been shown that the dorsolateral prefrontal cortex (DPFC) and cerebellum are interconnected in monkeys. This has been cited in support of the view that the cerebellum may be involved in cognitive functions, e.g. working memory. Six monkeys (Macaca fascicularis) were therefore trained on a classic test of working memory, the spatial delayed alternation (SDA) task, and also on a visual concurrent discrimination (VCD) task. Excitotoxic lesions were made in the lateral cerebellar nuclei, bilaterally, in three of the animals. When retested after surgery the lesioned animals were as quick to relearn both tasks as the remaining unoperated animals. However, when the response times (RT) for each task were directly compared, on the SDA task the monkeys with cerebellar lesions were relatively slow to decide where to respond. We argue that on the SDA task animals can prepare their responses between trials whereas this is not possible on the VCD task, and that the cerebellar lesions may disrupt this response preparation. We subsequently made bilateral lesions in the DPFC of the control animals and retested them on the SDA task. These monkeys failed to relearn the task. The results show that, unlike the dorsal prefrontal cortex, the cerebellum is not essential for working memory or the executive processes that are necessary for correct performance, though it may contribute to the preparation of responses.
The spatial representation of chemical structures in the antennal lobe of honeybees: steps towards the olfactory code
Authors: Sachse Silke , Rappert Angelika , Galizia C. Giovanni 
Published: March 2003

AbstractOdours are represented by specific ensembles of activated glomeruli in a combinatorial manner within the olfactory bulb of vertebrates or the antennal lobe (AL) of insects. Here, we optically measured glomerular calcium activities in vivo in the honeybee Apis mellifera during olfactory stimulation with 36 pure chemicals differing systematically in carbon chain length (C‐5–10) and functional group (aldehyde, ketone, alcohol, carboxylic acid and alkane). We show their glomerular representations in 38 morphologically identified glomeruli out of the honeybee's 160. We measured the molecular receptive range of identified glomeruli averaging up to 21 individuals. Of the 38 glomeruli measured, 23 show maximal activity in a specific range of chain length. Glomeruli preferentially responding to a functional group are also always broadly tuned to particular chain lengths. Furthermore, glomeruli with similar response spectra are often direct neighbours. The results allow conclusions about the interactions between olfactory receptors and odour molecules, and about the AL network.
Human striosomes are enriched in 5‐HT2A receptors: autoradiographical visualization with [3H]MDL100,907, [125I](±)DOI and [3H]ketanserin
Authors: López‐Giménez Juan F. , Mengod Guadalupe , Palacios José M. , Vilaró M. Teresa 
Published: March 2003

Abstract5‐HT2A receptors have been visualized with [3H]MDL100,907 in selected human brain areas by autoradiography. These areas included caudate and putamen, nucleus dentatus of the cerebellum, substantia nigra, nucleus raphe dorsalis, locus coeruleus and inferior olive. In the striatum [3H]MDL100,907 labelling was compared with the pattern obtained with [125I](±)DOI and [3H]ketanserin. [3H]MDL100,907 and [125I](±)DOI showed an identical patchy distribution which was hardly observed with [3H]ketanserin. In the remaining regions, [3H]MDL100,907 and [3H]ketanserin autoradiographical signals and percentage of specific binding were compared. Whereas the pattern of distribution was identical for both radioligands, [3H]MDL100,907 presented a much lower percentage of nonspecific binding compared with [3H]ketanserin. These results confirm the presence of 5‐HT2A receptors in human striosomes and in those areas where [3H]ketanserin presented a high nonspecific binding, and they highlight the advantage of using [3H]MDL100,907 to visualize these receptors.