bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subunit‐selective modulation of GABAA receptors by the non‐steroidal anti‐inflammatory agent, mefenamic acid
Authors: Halliwell R. F. , Thomas P. , Patten D. , James C. H. , Martinez‐Torres A. , Miledi R. , Smart T. G. 
Published: March 2003

AbstractMefenamic acid (MFA) has anti‐convulsant and pro‐convulsant effects in vivo, and has been shown to potentiate and inhibit GABAA (γ‐aminobutyric acid) receptors in vitro. In this study, whole‐cell currents were recorded from Xenopus oocytes and human embryonic kidney (HEK) cells expressing human recombinant GABAA receptors to resolve the molecular mechanisms by which MFA modulates GABAA receptor function. We demonstrate that MFA potentiated GABA‐activated currents for α1β2 γ2S (EC50 = 3.2 ± 0.5 μm), but not for α1β1 γ2S receptors. MFA also enhanced GABA‐activated responses and directly activated α1β2/β3 GABAA receptors, but inhibited responses to GABA on α1β1 constructs (IC50 = 40 ± 7.2 μm). A comparison of β1, β2 and β3 subunits suggested that the positive modulatory action of MFA involved asparagine (N) 290 in the second transmembrane domain (TM2) of the β2 and β3 subunits. Mutation of N290 to serine (S) markedly reduced modulation by MFA in α1β2(N290S)γ2S receptors, whereas α1β1(S290N)γ2S constructs revealed potentiated responses to GABA (EC50 = 7.8 ± 1.7 μm) and direct activation by MFA. The potentiation by MFA displayed voltage sensitivity. The direct activation, potentiation and inhibitory aspects of MFA action were predominantly conferred by the β subunits as the spontaneously active homomeric β1 and β3 receptors were susceptible to modulation by MFA. Molecular comparisons of MFA, loreclezole and etomidate, agents which exhibit similar selectivity for GABAA receptors, revealed their ability to adopt similar structural conformations. This study indicates that N290 in TM2 of β2 and β3 subunits is important for the regulation of GABAA receptor function by MFA. Our data provide a potential molecular mechanism for the complex central effects of MFA in vivo.
Increased glutathione levels in neurochemically identified fibre systems in the aged rat lumbar motor nuclei
Authors: Ramírez‐León Vania , Kullberg Susanna , Hjelle Ole Petter , Ottersen Ole Petter , Ulfhake Brun 
Published: March 2003

AbstractThe spinal cord motor nuclei have been the focus of a number of investigations exploring neurodegenerative mechanisms, e.g. excitotoxicity mediated by glutamate and oxidative stress. Here, high‐resolution quantitative post‐embedding immunocytochemistry with antibodies to oxidized and reduced glutathione (GSH), an ubiquitously expressed scavenger of free radicals, was used to examine if GSH synthesis is upregulated pre‐ and/or postsynaptically in the lumbar motor nuclei of aged (30 month old) rats. The purpose was, moreover, to resolve the extent of correlation between GSH expression, transmitter identity and degenerative changes. Tissue from young adult rats was co‐processed for comparison. The quantitative immunogold analysis revealed an increase in GSH‐immunoreactivity in both pre‐ and postsynaptic compartments in the lumbar motor nuclei of aged rats. Presynaptically, the enrichment of GSH‐immunoreactivity was seen in axonal boutons of normal appearance, and was furthermore restricted to the extra‐mitochondrial compartment. Postsynaptically, the aged rats disclosed, in comparison with young adults, higher values for GSH‐immunoreactivity both over mitochondria (+49%) and cytoplasmic matrix (+130%). When analysing the transmitter identity of the bouton profiles, it turned out that close to 50% of all glutamate‐immunoreactive boutons in the aged rats contained very high levels (> 40 gold particles/μm2) of GSH‐immunoreactivity. Strong GSH‐immunoreactivity was also a typical feature of a subset of axon terminal‐ and axon fibre‐like profiles in the aged rat that showed signs of axon dystrophy and degeneration. When comparing with normally appearing axon fibre profiles located in close vicinity, the population of aberrant axons had higher average levels of glutamate‐immunoreactivity (+93%), and lower average levels of glycine‐immunoreactivity (–88%). No difference was seen regarding the levels of GABA. The results of this study lend support to the idea that aging in the spinal cord motor nuclei is associated with an increased oxidative stress and indicate that different transmitter systems are differentially affected by the degenerative process.
Distribution of the voltage‐dependent calcium channel α1G subunit mRNA and protein throughout the mature rat brain
Authors: Craig P. J. , Beattie R. E. , Folly E. A. , Reeves M. B. , Priestley J. V. , Carney S. L. , Sher E. , Perez‐Reyes E. , Volsen S. G. 
Published: March 2003

AbstractThe molecular identity of a gene which encodes the pore‐forming subunit (α1G) of a member of the family of low‐voltage‐activated, T‐type, voltage‐dependent calcium channels has been described recently. Although northern mRNA analyses have shown α1G to be expressed predominantly in the brain, the detailed cellular distribution of this protein in the central nervous system (CNS) has not yet been reported. The current study describes the preparation of a subunit specific α1G riboprobe and antiserum which have been used in parallel in situ mRNA hybridization and immunohistochemical studies to localize α1G in the mature rat brain. Both α1G mRNA and protein were widely distributed throughout the brain, but variations were observed in the relative level of expression in discrete nuclei. Immunoreactivity for α1G was typically localized in both the soma and dendrites of many neurons. Whilst α1G protein and mRNA expression were often observed in cells known to exhibit T‐type current activity, some was also noted in regions, e.g. cerebellar granule cells, in which T‐type activity has not been described. These observations may reflect differences between the subcellular distribution of channels that can be identified by immunohistochemical methods compared with electrophysiological techniques.
Clonal expansion and cell dispersion in the developing mouse retina
Authors: Reese B. E. , Necessary B. D. , Tam P. P. L. , Faulkner‐Jones B. , Tan S. ‐S. 
Published: March 2003

AbstractThe present study has used two different approaches for labelling progenitor cells at the optic vesicle stage in order to examine patterns of clonal expansion and cellular dispersion within the developing retina. X‐inactivation transgenic mice and chimeric mice expressing the lacZ reporter transgene were examined during development and in adulthood to study the radial and tangential dispersion of proliferating neuroepithelial cells and postmitotic retinal cells of known identities. Chimeric retinas were used to measure tangential dispersion distances, while transgenic retinas were used to assess the frequency of tangential dispersion for individual populations of retinal neurons. Tangential dispersion is shown to be a universal feature of particular retinal cell types, being contrasted with the strictly radial dispersion of other cells. Tangential dispersion is a relatively short‐distance phenomenon, with distinct dispersion distances characteristic for cone, horizontal, amacrine and ganglion cells. Embryonic and postnatal retinas show that tangential dispersion occurs at different times for these distinct cell types, associated with their times of differentiation rather than their neurogenetic periods. These developmental results rule out the possibility that tangential dispersion is due to a passive displacement produced by the proliferation of later‐born cells, or to the lateral dispersion of a dividing sibling; rather, they are consistent with the hypothesis that tangential dispersion plays a role in the establishment of the orderly spatial distribution of retinal mosaics.
Filial imprinting in domestic chicks is associated with spine pruning in the associative area, dorsocaudal neostriatum
Authors: Bock Jörg , Braun Katharina 
Published: March 2003

AbstractJuvenile emotionally modulated learning events are fundamental for the normal development of socio‐emotional competence and intellectual capabilities. Filial imprinting in the domestic chick provides a suitable model to investigate the neural mechanisms underlying such juvenile learning events. The forebrain area dorsocaudal neostriatum (Ndc), a multimodal integration area and presumed equivalent to mammalian parietotemporal association cortices, has been shown to be critically involved in this learning process. We investigated whether filial imprinting is associated with changes of synaptic connectivity in the Ndc. Quantitative measurements of spine densities of a large neuron type in the Ndc revealed a massive pruning of spine synapses after filial imprinting. Compared with 7‐day‐old naive control chicks, imprinted chicks displayed significantly lower spine frequencies on all dendritic segments. Since the average length of the dendritic segments did not change during imprinting, these results can be interpreted as a reduction of the absolute number of spine synapses on this neuron type. In a control region, the primary sensory forebrain area ectostriatum, spine density and dendritic length remained unchanged. These results indicate that synaptic pruning may represent a mechanism of selective synaptic reorganization in higher associative forebrain areas as a fundamental feature of juvenile learning events.
Differential coupling of G‐protein‐linked receptors to Ca2+ mobilization through inositol(1,4,5)trisphosphate or ryanodine receptors in cerebellar granule cells in primary culture
Authors: Del Río E. , Mclaughlin Mark , Downes C. P. , Nicholls D. G. 
Published: March 2003

AbstractRat cerebellar granule cells in primary culture possess muscarinic, metabotropic glutamatergic, histaminergic and α‐adrenergic receptors which couple to phosphoinositide‐specific phospholipase C. We have determined the ability of these receptors to elevate inositol(1,4,5)trisphosphate and to release intracellular calcium, in order to establish the correlation between these two responses. In resting cerebellar granule cells, only the muscarinic agonist carbachol evoked significant increases in both inositol(1,4,5)trisphosphate and cytoplasmic free Ca2+. Mild depolarization (20 mm KCl) enhanced inositol(1,4,5)trisphosphate elevation by carbachol and histamine, but not by noradrenaline or the metabotropic glutamate agonist 1S,3R ACPD. In contrast, Ca2+‐release responses were modified differently by 20 mm KCl‐depolarization: the responses to carbachol, histamine and 1S,3R ACPD, but not the responses to noradrenaline, were markedly enhanced. The contribution of ryanodine‐sensitive Ca2+‐release channels (ryanodine receptors) to the calcium release signal in depolarized cells was determined. Ryanodine (10 μm) inhibited most effectively the cytoplasmic Ca2+ elevation evoked by 1S,3R ACPD (> 90%), while Ca2+ release upon stimulation by carbachol and histamine was only inhibited by ≈ 60% and remained larger than in the absence of KCl. Our data are consistent with a specific coupling between metabotropic glutamate receptors and ryanodine‐sensitive Ca2+‐release channels which may not require generation of inositol(1,4,5)trisphosphate.
β‐Thymosin, a modulator of the actin cytoskeleton is increased in regenerating retinal ganglion cells
Authors: Roth Lukas W. A. , Bormann Peter , Wiederkehr Christa , Reinhard Eva 
Published: March 2003

Abstractβ‐Thymosins are actin monomer‐binding polypeptides that are expressed in a neuronal growth‐specific manner during embryonic development. Here, we show that regenerating retinal ganglion cells and non‐neuronal cells of the optic nerve transiently activate β‐thymosin transcription after optic nerve lesion in the zebrafish. In retinal cell cultures, β‐thymosin is found at highest concentration in growth cones, branching points and varicosities of neurite‐extending retinal ganglion cells. These places often exhibit reduced phalloidin staining, indicating that β‐thymosin promotes the disassembly of actin filaments. β‐Thymosin distribution within neurons in culture is distinct from actin, tubulin and the actin‐severing protein gelsolin. Ectopic expression of β‐thymosin in a central nervous system (CNS) catecholaminergic cell line leads to alterations in the shape of the cell bodies and neurites. β‐Thymosin‐positive cells spread more fully and exhibit an excessive degree of branching. We partially cloned two other actin‐binding proteins, profilin and gelsolin, and analysed their expression patterns. Profilin is constitutively expressed in virtually all cells. Gelsolin, like β‐thymosin, is selectively increased in regenerating retinal ganglion cells. During development, however, gelsolin mRNA is not detected in the nervous system. These findings indicate that distinct mechanisms control the actin cytoskeleton in embryonic and regenerating neurons, and that β‐thymosin may be a major regulator of actin dynamics in the zebrafish CNS.
The cellular and developmental expression of hrs‐2 in rat
Authors: Tsujimoto S. , Pelto‐Huikko M. , Aitola M. , Meister B. , Vik‐Mo E. O. , Davanger S. , Scheller R. H. , Bean A. J. 
Published: March 2003

AbstractThe molecular events underlying vesicular trafficking probably involve the formation and dissolution of protein complexes between integral components of the vesicle and its target membrane. SNAP‐25 is associated with the plasma membrane and is a component of a core protein complex thought to be essential for neurotransmitter release. We have previously characterized a protein, hrs‐2, that interacts with SNAP‐25 and inhibits secretion from permeabilized PC12 cells. The cellular localization and developmental expression patterns of a number of proteins involved in the secretion machinery have been documented. To understand more about the possible cellular role of hrs‐2, we have examined hrs‐2 distribution, developmental expression and subcellular localization in rat tissues and cell lines. We show herein that the distribution of hrs‐2 in brain and periphery parallels that of SNAP‐23/25, and that recombinant hrs‐2 binds to both SNAP‐23 and SNAP‐25. Hrs‐2 mRNA and protein are found almost ubiquitously in neurons in the brain. Hrs‐2 mRNA is expressed in the neural tube at E10 and thereafter mRNA and protein levels remain relatively constant in the whole brain through adulthood. In cultured PC12 cells, endogenous hrs‐2 is expressed in the cytoplasm and on the limiting membranes of multivesicular bodies. Overexpression of hrs‐2 in mammalian cells results in the appearance of large intracellular compartments that are labelled with hrs‐2 antibodies. The wide distribution, the interaction with SNAP‐23 and the localization on multivesicular body membranes suggest a general role for hrs‐2 in cellular machinery.
Effects of juvenile isolation and morphine treatment on social interactions and opioid receptors in adult rats: behavioural and autoradiographic studies
Authors: Van den Berg Caroline L. , Van Ree Jan M. , Spruijt Berry M. , Kitchen Ian 
Published: March 2003

AbstractThe consequences of juvenile isolation and morphine treatment during the isolation period on (social) behaviour and μ‐, δ‐ and κ‐opioid receptors in adulthood were investigated by using a social interaction test and in vitro autoradiography in rats. Juvenile isolation reduced social exploration in adults. Morphine treatment counteracted this reduction in isolated rats, but decreased social exploration in nonisolated rats. Self‐grooming and nonsocial exploration were enhanced after juvenile isolation. Morphine treatment had no effect on self‐grooming, but suppressed nonsocial exploration in isolated rats. With respect to the opioid receptors, juvenile isolation resulted in regiospecific increases in μ‐binding sites with a 58% increase in the basolateral amygdala and a 33% increase in the bed nucleus of stria terminalis. Morphine treatment in isolated rats reversed this upregulation in both areas. The number of δ‐binding sites did not differ between the experimental groups. A general upregulation of κ‐binding sites was observed after juvenile isolation, predominantly in the cortical regions, the hippocampus and the substantia nigra. Morphine treatment did not affect the upregulation of κ‐receptors. The results show that juvenile isolation during the play period causes long‐term effects on social and nonsocial behaviours and on the number of μ‐ and κ‐ but not δ‐opioid receptors in distinct brain areas. The number of μ‐receptors in the basolateral amygdala appears to be negatively correlated with the amount of social exploration in adult rats.
Morphology, morphometry and probability mapping of the pars opercularis of the inferior frontal gyrus: an in vivo MRI analysis
Authors: Tomaiuolo F. , MacDonald J. D. , Caramanos Z. , Posner G. , Chiavaras M. , Evans A. C. , Petrides M. 
Published: March 2003

AbstractThe pars opercularis occupies the posterior part of the inferior frontal gyrus. Electrical stimulation or damage of this region interferes with language production. The present study investigated the morphology and morphometry of the pars opercularis in 108 normal adult human cerebral hemispheres by means of magnetic resonance imaging. The brain images were transformed into a standardized proportional steoreotaxic space (i.e. that of Talairach and Tournoux) in order to minimize interindividual brain size variability. There was considerable variability in the shape and location of the pars opercularis across brains and between cerebral hemispheres. There was no significant difference or correlation between left and right hemisphere grey matter volumes. There was also no significant difference between sex and side of asymmetry of the pars opercularis. A probability map of the pars opercularis was constructed by averaging its location and extent in each individual normalized brain into Talairach space to aid in localization of activity changes in functional neuroimaging studies.
Calcium channel heterogeneity among cone photoreceptors in the tree shrew retina
Authors: Morgans Catherine W. 
Published: March 2003

AbstractRetinal photoreceptors are depolarized in darkness and release neurotransmitter tonically. They respond to light by hyperpolarization and a concomitant reduction in transmitter release. The calcium‐dependent release of transmitter is coupled to graded changes in membrane potential by L‐type calcium channels in the photoreceptor terminals. This paper reports the immuno‐localization of an L‐type channel α1D subunit to most, but not all, synaptic terminals of cones in the tree shrew retina. Double labelling for the α1D subunit and the plasma membrane Ca2+‐ATPase, which has been shown to be present in all tree shrew cones, revealed a subpopulation of cone terminals that did not react with the α1D antibody. The nonimmunoreactive synaptic terminals represented ≈ 5.8% of the total and formed a highly regular array across the retina reminiscent of the blue cones. Double‐staining for the α1D subunit and blue cone opsin confirmed that these are the blue cones. The observed differences in calcium channel immunoreactivity between long and short wavelength cones points to previously unsuspected heterogeneity in the molecular machinery governing transmitter release from spectrally different cone types.
Partial denervation of the whiskerpad in adult mice: altered patterns of metabolic activity in barrel cortex
Authors: Bronchti Gilles , Corthésy Marc‐Etienne , Welker Egbert 
Published: March 2003

AbstractOne hundred days after unilateral C‐row nerve transection in the adult mouse whiskerpad, the caudal follicles of row C are reinnervated with ≈ 80 % of the original number of axons [Corthésy, M.‐E., Bronchti, G. & Welker, E. (1999) Eur. J. Neurosci., 11, 2835–2846]. To what extent is this reinnervation functional, and how does it interact with the enlargement of the functional representation of neighbouring rows subsequent to the denervation? Using the autoradiographic deoxyglucose method, we studied the whisker representation at the level of the barrel cortex 100 days post lesionem. We stimulated whiskers belonging to the denervated row C, the neighbouring rows B and D, or to all five rows A–E. The deoxyglucose uptake was measured in tangential sections through layer IV. The results indicate that, 100 days post lesionem, whiskers of row C reactivate their cortical barrels. However, (i) the magnitude of this cortical response was reduced; (ii) row C barrels were equivalently activated by the stimulation of the neighbouring rows; and (iii) when all whiskers were stimulated, we observed a significantly reduced deoxyglucose uptake over the representation of nonlesioned whiskers of rows D and E. Therefore, 100 days after the peripheral nerve lesion the reinnervation of the whiskerpad had not restored a normal pattern of activation at the level of the barrel cortex. We propose that this is due to a modified interaction between the representations of the various rows of follicles at the cortical level that does not return to normal.
Partial denervation of the whiskerpad in adult mice: pattern and origin of reinnervation
Authors: Corthésy Marc‐Etienne , Bronchti Gilles , Welker Egbert 
Published: March 2003

AbstractWe studied sensory organ reinnervation after nerve transection in the mouse whisker‐to‐barrel pathway. In one set of adult mice, we determined at light microscopy level the number of fibres reaching the caudal whisker follicles 5, 15, 20, 60, 100 days and 1 year after transection of the sensory nerve of row C. Regenerated fibres were first detected 15 days post lesionem (p.l.) and myelin first observed at 20 days. Between 60 and 100 days, the number of fibres stayed at ≈ 80% of the values obtained in control animals. At that time, myelinated fibres reached only 58% of their number in controls. At the electron microscopy level, these fibres differ from control ones by a smaller fibre diameter. The innervation of follicles of adjacent rows was not modified, indicating that follicular reinnervation is row specific. We checked this feature by injecting in another set of mice the denervated follicles and the adjacent ones with distinct retrograde tracers 45 days and 1 year after nerve transection. The percentage of double‐labelled neurons in the Gasserian ganglion did not increase in experimental animals. This confirms the absence of colonization of intact follicles by regenerating fibres and indicates that reinnervation of the whisker follicles takes place by regeneration of the degenerated axons without collateral reinnervation. The companion paper describes the pattern of activation of the barrel cortex relative to the present findings.