bluuebunny/crossref_metadata_2025_split huggingface dataset:
Developmental Loss of GABA‐ and Glycine‐induced Depolarization and Ca2+ Transients in Embryonic Rat Dorsal Horn Neurons in Culture
Authors: Wang Jian , Reichling David B. , Kyrozis Andreas , MacDermott Amy B. 
Published: April 2006

AbstractMore than 90% of dorsal horn neurons from embryonic day 15–16 rats responded to the inhibitory amino acids GABA and glycine by a transient elevation of intracellular Ca2+ concentration ([Ca2+]i) when maintained in culture for <1 week. This [Ca2+]i response has previously been shown to be due to depolarization and subsequent Ca2+ entry through voltage‐gated Ca2+ channels following activation of bicuculline‐sensitive GABAA receptors and strychnine‐sensitive glycine receptors. Both the number of cells responding to GABA and glycine and the amplitude of the [Ca2+]i response diminished over time in culture. By 30 days in culture, none of the cells responded to GABA, muscimol or glycine by elevation of [Ca2+]i. The loss of the [Ca2+]i response was not due to a change in the abundance or the properties of voltage‐gated Ca2+ channels, since over the same period of time dorsal horn neurons showed a large increase in the amplitude of the [Ca2+]i transient in response to 30 mM K+. Nor was the loss of the [Ca2+]i response due to a loss of GABA and glycine receptors. Instead, the decrease in the [Ca2+]i response over time paralleled a similar change in the electrophysiological responses. More than 90% of the neurons tested were depolarized in response to inhibitory amino acids during the first week in culture. After 30 days, all neurons tested responded to GABA and glycine with a hyperpolarization. These observations add support to the suggestion that GABA and glycine may excite dorsal horn neurons earlyin development and play a role in postmitotic differentiation.
Opposing Excitatory and Inhibitory Influences from the Cerebellum and Basal Ganglia Converge on the Superior Colliculus: an Electrophysiological Investigation in the Rat
Authors: Westby G. W. Max , Collinson Christine , Redgrave Peter , Dean Paul 
Published: April 2006

AbstractWe recently showed (Westby et al., Eur. J. Neurosci., 5, 1378–1388, 1993) that the cerebellar interpositus nucleus is a source of excitatory drive for a population of spontaneously active neurons in the lateral intermediate layers of the contralateral superior colliculus. Anatomical and physiological studies have shown that this region of the colliculus contains cells of origin of the crossed descending tectoreticulospinal tract and receives GABAergic input from the ipsilateral basal ganglia. In the present study we tested the hypothesis that the same neurons receiving excitatory drive from the cerebellum also receive tonic inhibitory input from the substantia nigra pars reticulata. From a sample of 73 spontaneously active collicular cells we found that in 53% the firing rate was suppressed by GABA microinjection into the contralateral deep cerebellar nuclei; a further 15% showed a frequency increase. Of the collicular cells identified as receiving excitatory cerebellar input, 85% were found to be disinhibited by nigral GABA microinjection. The remainder were all inhibited by nigral GABA. These data show that the main excitatory influence from the cerebellum and the main inhibitory influence from the substantia nigra converge on at least one population of spontaneously active cells in the lateral intermediate layers of the superior colliculus. This finding is discussed in relation to the possible function of these spontaneous cells in movement control and nociception.
Regulation of Neuropeptides in Adult Rat Forebrain by the Neurotrophins BDNF and NGF
Authors: Croll Susan D. , Wiegand Stanley J. , Anderson Keith D. , Lindsay Ronald M. , Nawa Hiroyuki 
Published: April 2006

AbstractThe expression of neuropeptides and neurotrophic factors is altered in the hippocampus after seizure induction in rats. Because the increase in brain‐derived neurotrophic factor (BDNF) and nerve growth factor (NGF) mRNAs precede changes in neuropeptide expression after seizure, it is possible that BDNF and NGF mediate subsequent alterations in peptide expression. To test this hypothesis directly, BDNF or NGF was infused into the hippocampus and cortex of adult rats. To ascertain the regional specificity of any observed effects of neurotrophin administration on neuropeptide expression, infusions into the striatum were also studied. To control for specificity, vehicle was also infused into the same sites. Peptide and mRNA alterations were assessed by Northern analysis, immunohistochemistry and radioimmunoassay. BDNF produced elevations of peptide and mRNA for neuropeptide Y and cholecystokinin in hippocampus and cortex, and somatostatin in cortex. BDNF increased mRNAs for neuropeptide Y, cholecystokinin, substance P and dynorphin in striatum. In contrast, BDNF decreased dynorphin peptide and mRNA in hippocampus. NGF's effects were limited to small mRNA increases, without corresponding changes in peptide levels, for neuropeptide Y in hippocampus and striatum, substance P in cortex and cholecystokinin in striatum. The distinct and limited effects of NGF infusion on neuropeptide expression demonstrate that BDNF's effects are not non‐specific results of protein infusion into the brain. These findings indicate that BDNF may play a regionally specific role in modulating neuropeptide expression in the normal brain as well as in various pathophysiological states.
Low Density, but not High Density, C6 Glioma Cells Support Dorsal Root Ganglion and Sympathetic Ganglion Neurite Growth
Authors: Watanabe Eiji , Hosokawa Hiroshi , Kobayashi Hiroaki , Murakami Fujio 
Published: April 2006

AbstractAccumulating evidence suggests that an inhibitory influence of the environment on growth cones plays a crucial role in development and regeneration of neuronal projections. Oligodendrocyte‐associated neurite growth inhibiting substance is one of the most extensively studied molecules. Molecular biological studies, however, remain slow in progress. Although finding clonal cells that express such factors would facilitate the analysis of inhibitory influences on neurite growth, few cell lines have been reported to express neurite growth inhibitor. We therefore investigated the possibility of a clonal glial cell line to differentiate and express inhibitory or non‐permissive features for neurite outgrowth in culture. We chose the C6 glioblastoma cell line and examined neurite extension from chick dorsal root ganglion (DRG) explants. Neurites from embryonic day 9 DRG extensively grew on C6 cells that were cultured at low cell density, while they failed to grow on C6 cells cultured at high density, even in the presence of nerve growth factor in high concentrations. Membrane extract from high density C6 cells, when used as culture substratum, was less permissive for neurite outgrowth compared to extract from low density cells. Treatment of the membrane extract derived from high density C6 cells with trypsin made it less non‐permissive for neurite growth. These results suggest that C6 cells are induced to express a non‐permissive property for neurite outgrowth by culturing them at high density.
Ultrastructure and GABA Immunoreactivity in Layers 8 and 9 of the Optic Tectum of Xenopus laevis
Authors: Rybicka Krystyna Kielan , Udin Susan B. 
Published: April 2006

AbstractThis study presents an ultrastructural analysis of layers 8 and 9 in the optic tectum of Xenopus laevis. Retinotectal axons were labelled with horseradish peroxidase and tectal cells were labelled with antibody to GABA. Four distinct axonal and dendritic structures were identified. GABA‐negative axon terminals formed asymmetric synapses and were categorized as type a‐1 (which included retinotectal axons), characterized by medium size synaptic vesicles and pale mitochondria, and type a‐2 (non‐retinotectal) with large vesicles and dense mitochondria. GABA‐negative dendrites (type d) contained dense mitochondria, microtubules in the dendritic shafts, and dendritic spines devoid of microtubules. GABA‐positive structures contained small synaptic vesicles and dense mitochondria. Some dendrites (type D) were not only postsynaptic but were also presynaptic elements, as defined by the presence of vesicles and distinct synaptic clefts with symmetric specializations. GABA‐positive presynaptic structures were mostly located in vesicle‐filled, bulbous extensions of dendritic shafts and usually terminated onto dendritic spines. Some type D dendrites were the middle element in serial synapses, with input from either GABA‐positive or GABA‐negative structures and output to GABA‐negative structures. Retinotectal terminals were identified as one of the synaptic inputs to GABA‐positive processes. Glia were characterized by granular cytoplasm and large mitochondria, often displaying a crystalline matrix structure. These results indicate that GABA‐positive neurons are a prominent component of circuitry in the superficial layers of the tectum of Xenopus and that, as in mammals, they participate in serial synaptic arrangements in which retinotectal axons are the first element. These arrangements are consistent with complex processing of visual input to the tectum and a central role for inhibitory processes in the shaping of tectal responses.
Cortical Magnification Theory Fails to Predict Visual Recognition
Authors: Strasburger Hans , Rentschler Ingo , Harvey Lewis O. 
Published: April 2006

AbstractThe sense of form is poor in indirect view. Yet the cortical magnification theory asserts that the disadvantage can be made up by scaling the image size according to the spatial variation in the mapping of the retina onto the cortex. It is thus assumed that all visual information passes through a functionally homogeneous neural circuitry, with the spatial sampling of input signals varying across the visual field. We challenge this notion by showing that character recognition in the visual field cannot be accommodated by any concept of sole size scaling but requires increasing both size and contrast of the target being viewed. This finding is formalized into a hyperbolic law which states that target size multiplied by log contrast is constant across the visual field. We conclude that the scalar cortical magnification theory fails for character recognition since the latter depends on multidimensional pattern representations in higher, i.e. striate and prestriate, cortical areas.
Development of Tonotopy in the Inferior Colliculus II: 2‐DG Measurements in the Kitten
Authors: Ehret Günter , Romand Raymond 
Published: April 2006

AbstractThe development of size and tonotopy in the inferior colliculus of the kitten was studied using the [14C]2‐deoxyglucose technique and tone stimulation with 2 and 15 kHz at a maximum 110 dB sound pressure level. At 2 days of age, frequency‐specific labelling cannot be detected. Two kilohertz labelling is distinctly visible in the rostral and central inferior colliculus at day 6; 15 kHz labelling occurs first at day 11. In the rostral and central inferior colliculus, 2 kHz labelling starts at a ventral and central position and shifts dorsalwards and to a more lateral location between postnatal days 6 and 21. Such a shift is not seen in the caudal inferior colliculus. There, the focus of 2 kHz labelling remains rather constant; only the extension of the labelling increases in the older animals. In all parts of the inferior colliculus, 15 kHz labelling starts at a ventromedial position and shifts to a more lateral location while extending also more dorsalwards as the age increases. These changes in 15 kHz labelling continue up to 3 months. In addition to the ventromedial‐to‐dorsolateral shift and expansion of labelling, there is also a rostral‐to‐caudal gradient of maturation, in that in older animals frequency‐specific labelling reaches farther caudalwards. The reported changes in frequency representation in the inferior colliculus can be explained on the basis of a shift in frequency input and input sensitivity to the laminae of the inferior colliculus, mainly due to maturational changes within the cochlea and/or as a consequence of the increasing size of the inferior colliculus.
Reduced Synchronization in the Visual Cortex of Cats with Strabismic Amblyopia
Authors: Roelfsema Pieter R. , König Peter , Engel Andreas K. , Sireteanu Ruxandra , Singer Wolf 
Published: April 2006

AbstractSynchronous firing of spatially separate neurons was studied with multi‐electrode recordings in area 17 of the visual cortex of strabismic cats which had developed behaviourally verified amblyopia of the deviated eye. Responses of neurons were evoked with moving light bars or gratings of different spatial frequency. Neurons driven by the normal eye displayed stronger synchronization of their responses than neurons dominated by the amblyopic eye. These interocular differences were highly significant and particularly pronounced for grating stimuli of high spatial frequency. No interocular differences were noted with respect to the amplitudes of responses to the light bars and gratings. These results suggest reduced synchronization of population responses as a neurophysiological correlate of strabismic amblyopia and underline the importance of correlated firing of spatially separate cortical neurons for normal processing of visual information.
Muscarinic Receptor Profiles of Mouse Brain Astrocytes in Culture Vary With Their Tissue Of Origin but Differ From Those of Neurons
Authors: André C. , Santos G. Dos , Koulakoff A. 
Published: April 2006

AbstractThe two main cell populations in brain tissues are neurons and astrocytes. Cultures of both bear muscarinic acetylcholine receptors (mAChRs). Available data indicate that astrocyte mAChRs are heterogeneous, but the particular subtypes on these cells are not known, nor is there any information as to whether there is a regional variation in the mAChR profile of astrocytes. This paper describes the mAChR profiles of cultured astrocytes derived from the cerebral hemispheres, mesencephalon and medulla‐pons, and is a continuation of our study on cultures of neurons from these same tissues. Pharmacological studies showed that the astrocytes accumulated small amounts of mAChRs with distinct pharmacological profiles which, for a given area, differed from those of neurons in culture. Northern blot analyses showed transcripts for ml and m3 mAChRs only. Their concentrations differed from one cell population to another. Astrocyte cultures from the mesencephalon contained ml mRNA amounts close to those in the tissue. Thus, at least part of the mAChR profile in vitro might be a true reflection of the cell's properties in vivo. Functional studies showed that mAChRs mediate the stimulation of phosphoinositide turnover in all three astrocyte cultures, that the amplitude of this response varies greatly with the origin of the cell, and that two pharmacological subclasses, M1 and M1–2‐, are involved in these responses, but to different extents. Thus the CNS contains discrete astrocyte populations which in culture differ in their mAChR profiles at the molecular, the pharmacological and the functional levels.
Developmental Shift From Long‐term Depression to Long‐term Potentiation at the Mossy Fibre Synapses in the Rat Hippocampus
Authors: Battistin Tiziana , Cherubini Enrico 
Published: April 2006

AbstractDuring development, in the CA1 hippocampal region, long‐term potentiation (LTP) starts appearing at postnatal (P) day 7 and reaches its maximal expression towards the end of the second postnatal week. However, LTP is often preceded by long‐term depression (LTD), an activity‐dependent and long‐lasting reduction of synaptic strength. LTD can be induced by sustained, low‐frequency stimulation of the afferent pathway and is dependent on activation of N‐methyl‐D‐aspartate (NMDA) receptors. We report here that, in the CA3 hippocampal region, during a critical period of postnatal development, between P6 and P14, a high‐frequency stimulation train (100 Hz, 1 s) to the mossy fibres in the presence of the NMDA receptor antagonist (+)‐3‐(2‐carboxy‐piperazin‐4‐yl)‐propyl‐1‐phosphonic acid (CPP; 20 μM) induced LTD. The depression of the amplitude of the field excitatory postsynaptic potential (EPSP) was 28 ± 7% (n= 21). This form of LTD was NMDA‐independent and synapse‐specific. When a tetanus was applied in the presence of CPP and 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX; 50 μM), which blocked the field EPSP, it failed to induce LTD upon washout of CNQX. LTD was probably postsynaptic in origin since it did not affect paired‐pulse facilitation. A rise in extracellular calcium concentration (from 2 to 4 mM) produced LTP instead of LTD. At the end of the second postnatal week, the same high‐frequency stimulation train to the mossy fibres induced LTP as in adult neurons. Functional changes in synaptic connections during development may control membrane depolarization and the amount of intracellular calcium necessary to trigger either LTD or LTP.
Location and Anatomical Connections of a Paradoxical Sleep Induction Site in the Cat Ventral Pontine Tegmentum
Authors: Reinoso‐Suárez Fernando , de Andrés Isabel , Rodrigo‐Angulo Margarita L. , Rodríguez‐Veiga Elisia 
Published: April 2006

AbstractThe brainstem mechanisms for the generation of paradoxical sleep are under considerable debate. Previous experiments in cats have demonstrated that injections of the cholinergic agonist carbachol into the oral pontine tegmentum elicit paradoxical sleep behaviour and its polygraphic correlates. The different results on the pontine structures that mediate this effect do not agree. We report here that limited microinjections of a carbachol solution into the ventral part of the oral pontine reticular nucleus in the cat induce, with a short latency, a dramatic, long‐lasting increase in paradoxical sleep. Moreover, neuronal tracing experiments show that this pontine site is connected with brain structures responsible for the different bioelectric events of paradoxical sleep. These two facts suggest that the ventral part of the oral pontine reticular nucleus is a nodal link in the neuronal network underlying paradoxical sleep mechanisms.
Juvenile Visual Callosal Axons in Kittens Display Origin‐and Fate‐related Morphology and Distribution of Arbors
Authors: Aggoun‐Zouaoui Djamila , Innocenti Giorgio M. 
Published: April 2006

AbstractIn kittens, callosal axons originating either from medial area 17 (transient axons) or near the 17/18 border (mostly permanent axons) were labelled with anterogradely transported biocytin; they were reconstructed by computer from serial sections, and their morphologies compared at different ages. During the first and second postnatal weeks both sets of axons branched profusely in the white matter of the lateral gyrus and the number of branches increased with age. The most common type of axon ending was the growth cone; others may have been collapsing growth cones, branches in the process of elimination or early synaptic boutons. Axons from medial area 17 distributed over a broad territory, including the 17/18 border where callosal axons terminate in the adult cat, but without aiming specifically at any one area. The majority of axons and their branches terminated in the white matter or at the bottom of layer VI; exceptionally they extended further into the cortex. Most of the axons originating near the 17/18 border were different from those described above, and the difference increased with age. Although they also terminated profusely in the white matter of the lateral gyrus, most of the branches terminated near the contralateral 17/18 border; they frequently entered the grey matter up to the superficial layers and branched into it. During the third week, axons from medial area 17 were rarely found to extend beyond the corpus callosum, probably because they were in the process of being eliminated. In contrast, axons originating near the 17/18 border had increased their number of branches in the grey matter. In conclusion, during the first and second postnatal weeks axons grew and differentiated according to their origin, and this anticipated whether they would be maintained or eliminated. Neurotrophic signals, possibly from the white matter or the subplate, and growth‐inhibiting signals from area 17 may be involved in this process.
Involvement of Metabotropic and lonotropic Glutamate Receptors in Inositol Polyphosphate Formation in Carp Retinal Slices
Authors: Janssen‐Bienhold U. , Wenzel A. , Hannken T. , Weiler R. 
Published: April 2006

AbstractThe contribution of ionotropic and metabotropic glutamate receptors to inositol polyphosphate accumulation in carp retinal slices was investigated using myo‐[2‐3H]inositol prelabelling. In the presence of the glutamate agonists quisqualate, (RS)‐α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole propionic acid (AMPA) and trans‐(±)‐1‐amino‐1, 3‐cyclopentane‐dicarboxylic acid (t‐ACPD), formation of [3H]inositol phosphate was significantly increased in a dose‐dependent manner, with EC50 values of 350 nM, 1.5 μM and 10 μM respectively. The complete AMPA‐induced response and a large component of the quisqualate‐induced response were inhibited in a competitive manner when the ionotropic antagonist 6‐cyano‐7‐nitroquinoxaline‐2, 3‐dione (CNQX) was present. Furthermore, the remaining level of quisqualate‐induced [3H]inositol phosphate formation closely matched that produced by ACPD alone, and coincubation of AMPA and ACPD showed additive effects, suggesting that the quisqualate‐induced response resulted from coactivation of metabotropic and ionotropic glutamate receptors. The ionotropic component was partially reduced in the presence of cobalt, suggesting indirect effects resulting from synaptic interactions. We could exclude indirect effects through depolarization‐induced release of other neurotransmitters. Only serotonin (EC50 1 μM) and carbachol (at a concentration of 1 mM) stimulated [3H]inositol phosphate formation, but their antagonists did not affect the quisqualate response and coactivation with quisqualate and serotonin or carbachol resulted in additive effects. The ionotropic component was completely suppressed when Ca2+ was omitted from the medium and cobalt was present. This makes it likely that the ionotropic component resulted from Ca2+ entry through AMPA‐gated channels and subsequent Ca2+‐dependent activation of phospholipase C.
Galanin Receptor Binding Sites in Adult Rat Spinal Cord Respond Differentially to Neonatal Capsaicin, Dorsal Rhizotomy and Peripheral Axotomy
Authors: Kar S. , Quirion R. 
Published: April 2006

AbstractThe discrete distribution and possible changes in specific [125I]galanin binding sites were evaluated in the rat spinal cord following neonatal capsaicin treatment, dorsal rhizotomy and sciatic nerve section. The highest density of [125I]galanin binding sites in the normal rat spinal cord was particularly evident in the superficial layers of the dorsal horn whereas moderate to low amounts of labelling were associated with the deeper dorsal horn, areas around the central canal and the ventral horn. Capsaicin‐treated rats, compared to littermate controls, showed a significant bilateral increase in [125I]galanin binding in the superficial laminae of the dorsal horn. Similarly, unilateral dorsal rhizotomy evoked a significant increase in the density of [125I]galanin binding sites in the superficial dorsal horn ipsilateral to surgery. Section of the sciatic nerve, on the other hand, induced a significant depletion in [125I]galanin binding in laminae I and II of the ipsilateral dorsal horn. These results, in parallel to those reported for galanin immunoreactivity under similar conditions, suggest that [125I]galanin binding sites are preferentially located postsynaptically to the primary afferent fibre terminals in the dorsal horn of the spinal cord. Thus it seems that galanin, at the level of the dorsal spinal cord, regulates the processing of nociceptive information by acting on its own class of specific receptors located postsynaptically to primary sensory terminals.