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Receptor Subunits (receptor + subunit)
Kinds of Receptor Subunits Terms modified by Receptor Subunits Selected AbstractsGlutamate Receptor Subunit ,2 Is Highly Expressed in a Novel Population of Glial-Like Cells in Rat Pineal Glands in CultureJOURNAL OF NEUROCHEMISTRY, Issue 3 2000Shouki Yatsushiro Abstract: The mammalian pineal gland uses L-glutamate as an intercellular chemical transmitter to regulate negatively melatonin synthesis. To receive glutamate signals, pinealocytes express at least three kinds of glutamate receptors: metabotropic receptor types 3 and 5 and an ionotropic receptor, GluR1. In this study, we examined whether or not the fourth class of ionotropic receptor, ,, which is known for its nondefinitive molecular function and its unique expression pattern in brain, is expressed in pineal gland. RT-PCR analyses with specific probes indicated the expression of mRNA of ,2 but not that of ,1 in pineal gland and cultured pineal cells. Western blotting analysis with polyclonal antibodies specific to the carboxyl-terminal region of the ,2 receptor recognized a single 110-kDa polypeptide of cerebellar membranes and specifically immunostained Purkinje cells. The ,2 antibodies recognized a 110-kDa polypeptide of pineal membranes and specifically immunostained huge glial-like cells with the occasional presence of several long, branching processes in a pineal cell culture. ,2 is not uniformly distributed throughout the cells and is relatively abundant at the periphery of the cell bodies and long processes, where the terminals of synaptophysin-positive processes of pinealocytes, a site for glutamate secretion, are frequently present. The ,2-positive cells constitute a very minor population among total pineal cells (,0.03%). Double immunolabeling with ,2 antibodies and antibodies against marker proteins for pineal interstitial cells clearly distinguishes ,2-positive pineal cells and other known interstitial cells, including glial fibrillary acidic protein- or vimentin-positive glial-like cells. These results indicated that the ,2 glutamate receptor is expressed in a novel subpopulation of pineal glial-like cells in culture and suggest the presence of a glutamate-mediated intercellular signal transduction mechanism between pinealocytes and ,2-expressing cells. The pineal cells may provide a good experimental system for studies on the function of glutamate receptor ,2. [source] Characterization of dendritic spines in the Drosophila central nervous systemDEVELOPMENTAL NEUROBIOLOGY, Issue 4 2009Florian Leiss Abstract Dendritic spines are a characteristic feature of a number of neurons in the vertebrate nervous system and have been implicated in processes that include learning and memory. In spite of this, there has been no comprehensive analysis of the presence of spines in a classical genetic system, such as Drosophila, so far. Here, we demonstrate that a subset of processes along the dendrites of visual system interneurons in the adult fly central nervous system, called LPTCs, closely resemble vertebrate spines, based on a number of criteria. First, the morphology, size, and density of these processes are very similar to those of vertebrate spines. Second, they are enriched in actin and devoid of tubulin. Third, they are sites of synaptic connections based on confocal and electron microscopy. Importantly, they represent a preferential site of localization of an acetylcholine receptor subunit, suggesting that they are sites of excitatory synaptic input. Finally, their number is modulated by the level of the small GTPase dRac1. Our results provide a basis to dissect the genetics of dendritic spine formation and maintenance and the functional role of spines. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source] Critical and sensitive periods for reversing the effects of mechanosensory deprivation on behavior, nervous system, and development in Caenorhabditis elegansDEVELOPMENTAL NEUROBIOLOGY, Issue 11 2007Susan Rai Abstract In these studies the nematode Caenorhabditis elegans was used as a model to investigate ways to reverse the effects of mechanosensory deprivation on behavior and development. Rose et al. (J Neurosci 2005; 25:7159,7168) showed that worms reared in isolation responded significantly less to a mechanical tap stimulus, were significantly smaller, and expressed significantly lower levels of a postsynaptic glutamate receptor subunit on the command interneurons of the tap response circuit and a presynaptic vesicle marker in the tap sensory neurons compared with worms raised in groups. Here, brief mechanical stimulation at any time throughout development reversed the effects of isolation on the response to tap and on postsynaptic glutamate receptor expression on the command interneurons, suggesting there is no critical period for these measures. In contrast to the high level of plasticity in glutamate receptor subunit expression on the interneurons, low levels of stimulation only rescued vesicle expression in the tap sensory neurons early in development and progressively higher levels of stimulation were required as the worm developed, suggesting a sensitive period immediately after hatching, followed by a period of decreasing plasticity. Stimulation during the first three stages of larval development, but not later, rescued the effects of isolation on worm length, suggesting there is a critical period for this measure that ends in the third larval stage. These results indicate that different effects of early isolation required different amounts and/or timing of stimulation to be reversed. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Synaptic plasticity and functionality at the cone terminal of the developing zebrafish retinaDEVELOPMENTAL NEUROBIOLOGY, Issue 3 2003Oliver Biehlmaier Abstract Previous studies have analyzed photoreceptor development, some inner retina cell types, and specific neurotransmitters in the zebrafish retina. However, only minor attention has been paid to the morphology of the synaptic connection between photoreceptors and second order neurons even though it represents the transition from the light sensitive receptor to the neuronal network of the visual system. Here, we describe the appearance and differentiation of pre- and postsynaptic elements at cone synapses in the developing zebrafish retina together with the maturation of the directly connecting second order neurons and a dopaminergic third order feedback-neuron from the inner retina. Zebrafish larvae were examined at developmental stages from 2 to 7dpf (days postfertilization) and in the adult. Synaptic maturation at the photoreceptor terminals was examined with antibodies against synapse associated proteins. The appearance of synaptic plasticity at the so-called spinule-type synapses between cones and horizontal cells was assessed by electron microscopy, and the maturation of photoreceptor downstream connection was identified by immunocytochemistry for GluR4 (AMPA-type glutamate receptor subunit), protein kinase ,1 (mixed rod-cone bipolar cells), and tyrosine hydroxylase (dopaminergic interplexiform cells). We found that developing zebrafish retinas possess first synaptic structures at the cone terminal as early as 3.5dpf. Morphological maturation of these synapses at 3.5,4dpf, together with the presence of synapse associated proteins at 2.5dpf and the maturation of second order neurons by 5dpf, indicate functional synaptic connectivity and plasticity between the cones and their second order neurons already at 5dpf. However, the mere number of spinules and ribbons at 7dpf still remains below the adult values, indicating that synaptic functionality of the zebrafish retina is not entirely completed at this stage of development. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 222,236, 2003 [source] Association of a single nucleotide polymorphism in neuronal acetylcholine receptor subunit alpha 5 (CHRNA5) with smoking status and with ,pleasurable buzz' during early experimentation with smokingADDICTION, Issue 9 2008Richard Sherva ABSTRACT Aims To extend the previously identified association between a single nucleotide polymorphism (SNP) in neuronal acetylcholine receptor subunit alpha-5 (CHRNA5) and nicotine dependence to current smoking and initial smoking-experience phenotypes. Design, setting, participants Case,control association study with a community-based sample, comprising 363 Caucasians and 72 African Americans (203 cases, 232 controls). Measurements Cases had smoked , five cigarettes/day for , 5 years and had smoked at their current rate for the past 6 months. Controls had smoked between one and 100 cigarettes in their life-time, but never regularly. Participants also rated, retrospectively, pleasurable and displeasurable sensations experienced when they first smoked. We tested for associations between smoking phenotypes and the top 25 SNPs tested for association with nicotine dependence in a previous study. Findings A non-synonymous coding SNP in CHRNA5, rs16969968, was associated with case status [odds ratio (OR) = 1.5, P = 0.01] and, in Caucasians, with experiencing a pleasurable rush or buzz during the first cigarette (OR = 1.6, P = 0.01); these sensations were associated highly with current smoking (OR = 8.2, P = 0.0001). Conclusions We replicated the observation that the minor allele of rs16969968 affects smoking behavior, and extended these findings to sensitivity to smoking effects upon experimentation. While the ability to test genetic associations was limited by sample size, the polymorphism in the CHRNA5 subunit was shown to be associated significantly with enhanced pleasurable responses to initial cigarettes in regular smokers in an a priori test. The findings suggest that phenotypes related to subjective experiences upon smoking experimentation may mediate the development of nicotine dependence. [source] Requirement of the tumour suppressor APC for the clustering of PSD-95 and AMPA receptors in hippocampal neuronsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2007Atsushi Shimomura Abstract Mutations in the adenomatous polyposis coli (APC) gene are associated with familial adenomatous polyposis and sporadic colorectal tumours. The APC gene is expressed ubiquitously in various tissues, especially throughout the large intestine and central nervous system (CNS). In the CNS, the expression of the APC protein is highest during embryonic and early postnatal development. APC associates through its C-terminal region with postsynaptic density (PSD)-95, a neuronal protein that participates in synapse development. Here, we examined the involvement of APC in synaptogenesis. In cultured hippocampal neurons, both overexpression of a dominant-negative construct that disrupts the APC,PSD-95 interaction and knockdown of APC expression using small interfering RNA (siRNA) inhibited the clustering of PSD-95 and a glutamate receptor subunit, and reduced alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA)-induced activity of AMPA receptors; however, the clustering of an N -methyl- d -aspartate (NMDA) receptor subunit was unaffected. These results are suggestive of APC involvement in the development of glutamatergic synapses. [source] Impairment of eyeblink conditioning in GluR,2-mutant mice depends on the temporal overlap between conditioned and unconditioned stimuliEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001Yasushi Kishimoto Abstract Mice lacking the glutamate receptor subunit ,2 (GluR,2) are deficient in cerebellar long-term depression (LTD) at the parallel fibre,Purkinje cell synapses. We conducted delay and trace eyeblink conditioning with these mice, using various temporal intervals between the conditioned stimulus (CS) and unconditioned stimulus (US). During trace conditioning in which a stimulus-free trace interval (TI) of 250, 100 or 50 ms intervened between the 352-ms tone CS and 100-ms US, GluR,2-mutant mice learned as successfully as wild-type mice. Even in the paradigm with TI = 0 ms, in which the end of CS and onset of US are simultaneous, there was no difference between the GluR,2-mutant and wild-type mice in their acquisition of a conditioned response. However, in the delay paradigm in which the 452-ms CS overlapped temporally with the coterminating 100-ms US, GluR,2-mutant mice exhibited severe learning impairment. The present study together with our previous work [Kishimoto, Y., Kawahara, S., Suzuki, M., Mori, H., Mishina, M. & Kirino, Y. (2001) Eur. J. Neurosci.,13, 1249,1254], indicates that cerebellar LTD-independent learning is possible in paradigms without temporal overlap between the CS and US. On the other hand, GluR,2 and cerebellar LTD are essential for learning when there is CS,US temporal overlap, suggesting that the cerebellar neural substrates underlying eyeblink conditioning may change, depending on the temporal overlap of the CS and US. [source] Interleukin-6-induced proliferation of pre-B cells mediated by receptor complexes lacking the SHP2/SOCS3 recruitment sites revisitedFEBS JOURNAL, Issue 24 2001Kerstin Friederichs Interleukin-6 (IL-6) induces B-cell proliferation by binding to receptor complexes composed of a specific ,-receptor (gp80; CD126) and the signal transducing receptor subunit gp130 (CD130). Immediately after receptor complex activation, signal transducers and activators of transcription (STATs) 1 and 3 and the Src-homology domain-containing protein tyrosine phosphatase 2 (SHP2) are recruited to gp130 and subsequently tyrosine phosphorylated. The activated dimerized STATs translocate to the nucleus and bind to enhancer elements of IL-6-inducible genes. SHP2 acts as an adapter and links the Jak/STAT pathway to the Ras/Raf/MAPK cascade but it is also involved in signal attenuation. Whereas STAT3 activation appears to be crucial for all biological activities of IL-6, the requirement of SHP2-activation depends on the individual biological response analyzed. The requirement of SHP2 activation for the pre-B cell (Ba/F3) proliferation has been reported previously [Fukada, T., Hibi, M., Yamanaka, Y., Takahashi-Tezuka, M., Fujitani, Y., Yamaguchi, T., Nakajima, K. & Hirano, T. (1996) Immunity5, 449,460]. In contrast, we have recently demonstrated that the presence of a single STAT-recruitment site within gp130 is sufficient for IL-6- induced proliferation of Ba/F3 cells [Schmitz, J., Dahmen, H., Grimm, C., Gendo, C., Müller-Newen, G., Heinrich, P.C. & Schaper, F. (2000) J. Immunol.164, 848,854]. To unravel this discrepancy we analyzed the IL-6-induced dose-dependent proliferation of Ba/F3 cells mediated by receptor complexes lacking SHP2/SOCS3 recruitment sites. Surprisingly, pre-B cells, after stimulation with low amounts of IL-6, proliferate much more efficiently in the absence of the activated SHP2 than in the presence of the tyrosine phosphatase. Therefore, SHP2 activation appears to be relevant for IL-6-induced proliferation only after stimulation with very large amounts of IL-6. [source] Nicotinic acetylcholine receptor expression in the hippocampus of 27 mouse strains reveals novel inhibitory circuitryHIPPOCAMPUS, Issue 8 2008Lorise C. Gahring Abstract Mouse strains are well-characterized to exhibit differences in their physiological and behavioral responses to nicotine. This report examines the expression of the high-affinity nicotine binding receptor subunit, neuronal nicotinic receptor subunit alpha4 (nAChR,4), in the dorsal hippocampus of 27 inbred mouse strains. Multiple differences among mouse strains in the cellular expression of nAChR,4 between subregions of the hippocampal field are evident. Differences that we describe in the expression of nAChR,4 suggest mouse strains of diverse genetic origin could exhibit significant variation in how this receptor contributes to modulating intrahippocampal circuitry. These findings define a genetic frame-work in which the strain-specific responses to nicotine include underlying contributions by the varied anatomical context in which nAChRs are expressed. © 2008 Wiley-Liss, Inc. [source] Mouse chromosome 11 harbors genetic determinants of hippocampal strain-specific nicotinic receptor expressionHIPPOCAMPUS, Issue 8 2008Scott W. Rogers Abstract Differences between isogenic mouse strains in cellular expression of the neuronal nicotinic acetylcholine (ACh) receptor subunit alpha4 (nAChR,4) by the dorsal hippocampus are well known. To investigate further the genetic basis of these variations, expression of the nAChR,4 subunit was measured in congenic mouse lines derived from two strains exhibiting notable divergence in the expression of this subunit: C3H and C57BL/6. Congenic lines carrying reciprocally introgressed regions (quantitative trait loci; QTL) from chromosomes 4, 5, and 12 each retained the phenotype most closely associated with the parental strain. However, in congenic lines harboring the reciprocal transfer of a chromosome 11 QTL, a characteristic difference in the ratio of interneurons versus astrocytes expressing nAChR,4 in the CA1 region is reversed relative to the parental strain. These finding suggest that this chromosomal segment harbors genes that regulate strain distinct hippocampal morphology that is revealed by nAChR,4 expression. © 2008 Wiley-Liss, Inc. [source] Nicotinic ,5 subunit deletion locally reduces high-affinity agonist activation without altering nicotinic receptor numbersJOURNAL OF NEUROCHEMISTRY, Issue 1 2007Robert W. B. Brown Abstract Neuronal nicotinic acetylcholine receptor subunit ,5 mRNA is widely expressed in the CNS. An ,5 gene polymorphism has been implicated in behavioral differences between mouse strains, and ,5-null mutation induces profound changes in mouse acute responses to nicotine. In this study, we have examined the distribution and prevalence of ,5* nicotinic acetylcholine receptor in mouse brain, and quantified the effects of ,5-null mutation on pre-synaptic nicotinic acetylcholine receptor function (measured using synaptosomal 86Rb+ efflux) and overall [125I]epibatidine binding site expression. ,5* nicotinic acetylcholine receptor expression was found in nine of fifteen regions examined, although < 20% of the total nicotinic acetylcholine receptor population in any region contained ,5. Deletion of the ,5 subunit gene resulted in localized loss of function (thalamus, striatum), which was itself confined to the DH,E-sensitive receptor population. No changes in receptor expression were seen. Consequently, functional changes must occur as a result of altered function per unit of receptor. The selective depletion of high agonist activation affinity sites results in overall nicotinic function being reduced, and increases the overall agonist activation affinity. Together, these results describe the receptor-level changes underlying altered behavioral responses to nicotine in nicotinic acetylcholine receptor ,5 subunit-null mutants. [source] NSF binds calcium to regulate its interaction with AMPA receptor subunit GluR2JOURNAL OF NEUROCHEMISTRY, Issue 6 2007Jonathan G. Hanley Abstract N -ethylmaleimide-sensitive fusion protein (NSF) is essential for numerous Ca2+ -triggered vesicle trafficking events. It functions as a molecular chaperone to regulate trafficking protein complexes such as the soluble NSF attachment protein (SNAP) receptor complex and the ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR)-protein interacting with C-kinase (PICK1) complex. AMPAR trafficking is fundamental to processes of synaptic plasticity, which may underlie learning and memory. Changes in synaptic strength brought about by AMPAR trafficking are triggered by a post-synaptic influx of Ca2+, which may have numerous molecular targets including PICK1. NSF binds AMPAR subunit glutamate receptor subunit 2 (GluR2) and functions to maintain receptors at the synapse. In this study, it was showed that NSF is a Ca2+ -binding protein and that GluR2,NSF interactions are inhibited by the presence of 15 ,mol/L Ca2+. NSF Ca2+ -binding is reciprocally inhibited by the presence of GluR2 C-terminus. Mutant of NSF that binds Ca2+ with reduced affinity and binds GluR2 with reduced sensitivity to Ca2+ was identied. In addition, the interaction of ,SNAP with PICK1 is sensitive to Ca2+. This study demonstrates that the GluR2-NSF-,SNAP-PICK1 complex is regulated directly by Ca2+, allowing for the transduction of Ca2+ signals into concerted alterations in protein,protein interactions to bring about changes in AMPAR trafficking during synaptic plasticity. [source] Hypoxic damage to the periventricular white matter in neonatal brain: role of vascular endothelial growth factor, nitric oxide and excitotoxicityJOURNAL OF NEUROCHEMISTRY, Issue 4 2006Charanjit Kaur Abstract The present study examined factors that may be involved in the development of hypoxic periventricular white matter damage in the neonatal brain. Wistar rats (1-day old) were subjected to hypoxia and the periventricular white matter (corpus callosum) was examined for the mRNA and protein expression of hypoxia-inducible factor-1, (HIF-1,), endothelial, neuronal and inducible nitric oxide synthase (eNOS, nNOS and iNOS), vascular endothelial growth factor (VEGF) and N-methyl-D-aspartate receptor subunit 1 (NMDAR1) between 3 h and 14 days after hypoxic exposure by real-time RT-PCR, western blotting and immunohistochemistry. Up-regulated mRNA and protein expression of HIF-1,, VEGF, NMDAR1, eNOS, nNOS and iNOS in corpus callosum was observed in response to hypoxia. NMDAR1 and iNOS expression was found in the activated microglial cells, whereas VEGF was localized to astrocytes. An enzyme immunoassay showed that the VEGF concentration in corpus callosum was significantly higher up to 7 days after hypoxic exposure. NO levels, measured by colorimetric assay, were also significantly higher in hypoxic rats up to 14 days after hypoxic exposure as compared with the controls. A large number of axons undergoing degeneration were observed between 3 h and 7 days after the hypoxic exposure at electron-microscopic level. Our findings point towards the involvement of excitotoxicity, VEGF and NO in periventricular white matter damage in response to hypoxia. [source] The Caenorhabditis elegans lev-8 gene encodes a novel type of nicotinic acetylcholine receptor , subunitJOURNAL OF NEUROCHEMISTRY, Issue 1 2005Paula R. Towers Abstract We have cloned Caenorhabditis elegans lev-8 and demonstrated that it encodes a novel nicotinic acetylcholine receptor (nAChR) subunit (previously designated ACR-13), which has functional roles in body wall and uterine muscles as part of a levamisole-sensitive receptor. LEV-8 is an ,,subunit and is the first to be described from the ACR-8-like group, a new class of nAChR with atypical acetylcholine-binding site (loop C) and channel-lining motifs. A single base pair change in the first intron of lev-8 in lev-8(x15) mutants leads to alternative splicing and the introduction of a premature stop codon. lev-8(x15) worms are partially resistant to levamisole-induced egg laying and paralysis, phenotypes rescued by expression of the wild-type gene. lev-8(x15) worms also show reduced rates of pharyngeal pumping. Electrophysiological recordings from body wall muscle show that currents recorded in response to levamisole have reduced amplitude in lev-8(x15) compared with wild-type animals. Consistent with these phenotypic observations, green fluorescent protein fused to LEV-8 is expressed in body wall and uterine muscle, motor neurons and epithelial-derived socket cells. Thus, LEV-8 is a levamisole receptor subunit and exhibits the most diverse expression pattern of any invertebrate nAChR subunit studied to date. [source] Association of Markers in the 3, Region of the GluR5 Kainate Receptor Subunit Gene to Alcohol DependenceALCOHOLISM, Issue 5 2009Henry R. Kranzler Background:, Glutamate neurotransmission plays an important role in a variety of alcohol-related phenomena, including alcohol self-administration by both animals and humans. Because the risk for alcohol dependence (AD) is genetically influenced, genes encoding glutamate receptors are candidates to contribute to the risk for AD. We examined the role of variation in the 3, region of GRIK1, the gene that encodes the GluR5 receptor subunit of the kainic acid glutamate receptor, on risk for AD. We focused specifically on this gene because topiramate, a glutamate modulator that binds to the GluR5 subunit, has shown robust efficacy in the treatment of AD. Methods:, We genotyped 7 single nucleotide polymorphisms (SNPs) in the 3,-half of GRIK1, which includes 3 differentially spliced exons, in a sample of EA control subjects (n = 507) and subjects with AD (n = 1,057). Results:, We found nominally significant evidence of association to AD for 3 SNPs (rs2832407 in intron 9, rs2186305 in intron 17, and rs2832387 in the 3,UTR). Empirical p -value estimation revealed that only rs2832407 was significantly associated to phenotype (p = 0.043). Discussion:, These findings provide support for the hypothesis that variation in the 3, portion of the gene encoding the GluR5 kainate receptor subunit contributes to the risk for AD. Further research is needed to ascertain whether this SNP is itself functional or whether the association reflects linkage disequilibrium with functional variation elsewhere in the gene and whether this SNP moderates topiramate's effects in the treatment of AD. [source] Lasting changes in NMDAR1 mRNA level in various regions of cerebral cortex in epileptogenesis of amygdaloid-kindled ratPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 5 2000Shiuichi Kikuchi MD Abstract The involvement of NMDA receptor subunit, NR1, with kindling phenomenon has been reported, but the role of NR1 in epileptogenesis is still unknown. We have examined the expression levels of NR1 mRNA in the cerebral cortices of amygdaloid-kindled rats. Northern blot analysis showed a significant increase in NR1 mRNA expression level in the ipsilateral frontal and temporal cortices at 4 weeks after the last generalized seizure. At the same time, NR1 mRNA decreased in the bilateral piriform cortices. These data suggest that NR1-mediated transmission may have an impact in the neurobiological basis of enduring epileptogenesis. [source] Environmental enrichment reverses cognitive and molecular deficits induced by developmental lead exposureANNALS OF NEUROLOGY, Issue 1 2003Tomás R. Guilarte PhD Long-term deficits in cognitive function are the principal effects of lead (Pb2+) exposure in children and can be modeled in experimental animals. Current therapeutic approaches in the treatment of childhood Pb2+ intoxication are not effective in reversing learning deficits once they have occurred. We report that environmental enrichment reverses long-term deficits in spatial learning produced by developmental Pb2+ exposure in rats. Enhanced learning performance of Pb2+ -exposed animals reared in an enriched environment was associated with recovery of deficits in N- methyl- D -aspartate receptor subunit 1 (NR1) mRNA and induction of brain-derived neurotrophic factor (BDNF) mRNA in the hippocampus. The effect of environmental enrichment on NR1 and BDNF gene expression was specific to Pb2+ -exposed animals and was present in the absence of changes in the NR2B subunit of the N- methyl- D -aspartate receptor, GluR1, ,CamKII, or PSD-95 gene expression measured in the same animals. Our findings demonstrate that the learning impairments and NR1 subunit mRNA deficits resulting from developmental Pb2+ exposure are reversible if the animals are provided with an enriched environment even after the exposure has occurred. We propose environmental enrichment as a basis for the treatment of childhood Pb2+ intoxication. [source] GABAB receptor function in the ileum and urinary bladder of wildtype and GABAB1 subunit null miceAUTONOMIC & AUTACOID PHARMACOLOGY, Issue 3 2002G. J. Sanger Summary1 GABAB1 receptor subunit knockout mice were generated and the effects of the GABAB receptor agonist, baclofen, were evaluated within the peripheral nervous system (PNS) of wildtype (+/+), heterozygote (+/,) and knockout (,/,) animals. For this purpose, neuronally-mediated responses were evoked in both the isolated ileum and urinary bladder, using selective electrical field stimulation (EFS). 2 In ileum resected from 4,8-week-old-mice, low frequencies of EFS (0.5 Hz) evoked irregular muscle contractions which were prevented by atropine 1 ,M and reduced by baclofen (33.4 ± 5.6%, 100 ,m). The latter effect was antagonized by the GABAB receptor antagonist CGP54626 0.2 ,m. Baclofen 100 ,m did not affect contractions of similar amplitude induced by carbachol, indicating that the ability of baclofen to inhibit cholinergic function in mouse ileum may be due to an action at prejunctional GABAB receptors. 3 To avoid the development of grand mal seizure by GABAB1 (,/,) mice, a behaviour observed when the mice were greater than 3 weeks old, it was necessary to study the effects of this knockout in 1,3-week-old-animals. However, at this age, EFS at 0.5 Hz did not evoke robust muscle contractions. Consequently we used EFS at 5 Hz, which did evoke cholinergically mediated contractions, found to be of similar amplitude in (+/+) and (+/,) mice, of both 1,3 weeks and 4,8 weeks of age. At this frequency of EFS, baclofen reduced the amplitude of the evoked contractions [n=6 (+/+) and n=5 (+/,), IC50 19.2 ± 4.8 ,m) and this effect was greatly reduced in the presence of CGP54626 0.2 ,m. 4 In urinary bladder from 1,3-week-old-mice, using higher frequencies of EFS to evoke clear, nerve-mediated contractions (10 Hz), baclofen 10,300 ,m concentration-dependently inhibited contractions in (+/+) mice (IC50 9.6 ± 3.8 ,m). This effect was inhibited by CGP54626 (0.2 ,m, 46.2 ± 13.6% inhibition, 300 ,m baclofen n=7) a concentration which, by itself, had no effect on the EFS-evoked contractions. 5 The effects of baclofen in both ileum and urinary bladder were absent in the GABAB1 receptor subunit (,/,) mice; however, responses to EFS were unaffected in (,/,) when compared to the (+/+) mice. 6 Our data suggest that, as in the central nervous system (CNS), the GABAB1 receptor subunit is an essential requirement for GABAB receptor function in the enteric and PNS. As such, these data do not provide a structural explanation for the existence of putative subtypes of GABAB receptor, suggested by studies such as those in which different rank-orders of GABAB agonist affinity have been reported in different tissues. [source] Cloned P2X receptor subunits in cerebellum and hippocampusDRUG DEVELOPMENT RESEARCH, Issue 1-2 2001Florentina Soto Abstract P2X receptor subunits have been found in the brain, with P2X2, P2X4, and P2X6 showing a high level of expression. Here, we review the findings about the distribution of P2X receptor subunits in cerebellum and hippocampus and discuss their implication on the possible roles of ATP as neurotransmitter/neuromodulator in the brain. Drug Dev. Res. 52:133,139, 2001. © 2001 Wiley-Liss, Inc. [source] Genetic Architecture of Idiopathic Generalized Epilepsy: Clinical Genetic Analysis of 55 Multiplex FamiliesEPILEPSIA, Issue 5 2004Carla Marini Summary: Purpose: In families with idiopathic generalized epilepsy (IGE), multiple IGE subsyndromes may occur. We performed a genetic study of IGE families to clarify the genetic relation of the IGE subsyndromes and to improve understanding of the mode(s) of inheritance. Methods: Clinical and genealogic data were obtained on probands with IGE and family members with a history of seizures. Families were grouped according to the probands' IGE subsyndrome: childhood absence epilepsy (CAE), juvenile absence epilepsy (JAE), juvenile myoclonic epilepsy (JME), and IGE with tonic,clonic seizures only (IGE-TCS). The subsyndromes in the relatives were analyzed. Mutations in genes encoding ,1 and ,2 ,-aminobutyric acid (GABA)-receptor subunits, ,1 and ,1 sodium channel subunits, and the chloride channel CLC-2 were sought. Results: Fifty-five families were studied. 122 (13%) of 937 first- and second-degree relatives had seizures. Phenotypic concordance within families of CAE and JME probands was 28 and 27%, respectively. JAE and IGE-TCS families had a much lower concordance (10 and 13%), and in the JAE group, 31% of relatives had CAE. JME was rare among affected relatives of CAE and JAE probands and vice versa. Mothers were more frequently affected than fathers. No GABA-receptor or sodium or chloride channel gene mutations were identified. Conclusions: The clinical genetic analysis of this set of families suggests that CAE and JAE share a close genetic relation, whereas JME is a more distinct entity. Febrile seizures and epilepsy with unclassified tonic,clonic seizures were frequent in affected relatives of all IGE individuals, perhaps representing a nonspecific susceptibility to seizures. A maternal effect also was seen. Our findings are consistent with an oligogenic model of inheritance. [source] Developmental maturation of ionotropic glutamate receptor subunits in rat vestibular nuclear neurons responsive to vertical linear accelerationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2008Suk-King Lai Abstract We investigated the maturation profile of subunits of ionotropic glutamate receptors in vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the vertical plane. The otolithic origin of Fos expression in these neurons was confirmed as a marker of functional activation when labyrinthectomized and/or stationary control rats contrasted by showing sporadically scattered Fos-labeled neurons in the vestibular nuclei. By double immunohistochemistry for Fos and one of the receptor subunits, otolith-related neurons that expressed either ,-amino-3-hydroxy-5-methyl-4-isoxazole-propionate or N -methyl- d -aspartate subunits were first identified in the medial vestibular nucleus, spinal vestibular nucleus and Group x by postnatal day (P)7, and in the lateral vestibular nucleus and Group y by P9. No double-labeled neurons were found in the superior vestibular nucleus. Within each vestibular subnucleus, these double-labeled neurons constituted ,90% of the total Fos-labeled neurons. The percentage of Fos-labeled neurons expressing the GluR1 or NR2A subunit showed developmental invariance in all subnuclei. For Fos-labeled neurons expressing the NR1 subunit, similar invariance was observed except that, in Group y, these neurons decreased from P14 onwards. For Fos-labeled neurons expressing the GluR2, GluR2/3, GluR4 or NR2B subunit, a significant decrease was found by the adult stage. In particular, those expressing the GluR4 subunit showed a two- to threefold decrease in the medial vestibular nucleus, spinal vestibular nucleus and Group y. Also, those expressing the NR2B subunit showed a twofold decrease in Group y. Taken together, the postsynaptic expression of ionotropic glutamate receptor subunits in different vestibular subnuclei suggests that glutamatergic transmission within subregions plays differential developmental roles in the coding of gravity-related vertical spatial information. [source] GluR3 subunit regulates sleep, breathing and seizure generationEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 5 2008Hendrik W. Steenland Abstract The functional role of GluR3 AMPA (,-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptor subunits has remained elusive. In vitro studies of genetic knockout mice have not yielded significant alterations in synaptic communication. However, behavioural approaches utilizing knockout mice have shown that the subunit may be involved in exploration and motor coordination, suggesting that in vivo methodologies may be more forthcoming. We tested the hypothesis that GluR3 subunits are involved in the modulation of neural network activity. We used a freely behaving mouse model to examine the effect of GluR3,/, on field potential recordings of electroencephalogram, vital functions (i.e. breathing and heart rate) and muscle tone across natural sleep and wakefulness states. We found that GluR3,/, mice virtually lack electroencephalographic signatures of NREM sleep (n = 9) as demonstrated by reduction in electroencephalogram power in the low-frequency bands (,1, ,2 and ,). In addition, three of nine GluR3,/, mice expressed seizure activity during wakefulness and sleep, suggesting that deletion of the GluR3 gene may predispose to seizure. GluR3 gene knockout also produced state-dependent respiratory modulation, with a selective reduction in breathing rate during behavioural inactivity. These findings show that GluR3 subunits have diverse neurophysiological impact, modulating oscillatory networks for sleep, breathing and seizure generation. Finally, this is the first study to demonstrate the feasibility of direct diaphragm electromyogram recordings in freely behaving mice. [source] Evidence for the involvement of purinergic P2X7 receptors in outer retinal processingEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2006Theresa Puthussery Abstract Extracellular ATP mediates fast excitatory neurotransmission in many regions of the central nervous system through activation of P2X receptors. Although several P2X receptor subunits have been identified in the mammalian retina, little is known about the functional role of these receptors in retinal signalling. The purpose of the present study was to investigate whether purinergic P2X7 receptors are involved in outer retinal processing by assessing receptor localization, degradation of extracellular ATP and the effect of functional activation of P2X7 receptors on the electroretinogram (ERG). Using light and electron microscopy, we demonstrated that P2X7 receptors are expressed postsynaptically on horizontal cell processes as well as presynaptically on photoreceptor synaptic terminals in both the rat and marmoset retina. Using an enzyme cytochemical method, we showed that ecto-ATPases are active in the outer plexiform layer of the rat retina, providing a mechanism by which purinergic synaptic transmission can be rapidly terminated. Finally, we evaluated the role of P2X7 receptors in retinal function by assessing changes to the ERG response of rats after intravitreal delivery of the P2X7 receptor agonist benzoyl benzoyl ATP (BzATP). Intravitreal injection of BzATP resulted in a sustained increase (up to 58%) in the amplitude of the photoreceptor-derived a-wave of the ERG. In contrast, BzATP caused a transient reduction in the rod- and cone-derived postreceptoral responses. These results provide three lines of evidence for the involvement of extracellular purines in outer retinal processing. [source] Presynaptic localization of an AMPA-type glutamate receptor in corticostriatal and thalamostriatal axon terminalsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2004Fumino Fujiyama Abstract The neostriatum is known to receive glutamatergic projections from the cerebral cortex and thalamic nuclei. Vesicular glutamate transporters 1 and 2 (VGluT1 and VGluT2) are located on axon terminals of corticostriatal and thalamostriatal afferents, respectively, whereas VGluT3 is found in axon terminals of cholinergic interneurons in the neostriatum. In the present study, the postsynaptic localization of ionotropic glutamate receptors was examined in rat neostriatum by the postembedding immunogold method for double labelling of VGluT and glutamate receptors. Immunoreactive gold particles for AMPA receptor subunits GluR1 and GluR2/3 were frequently found not only on postsynaptic but also on presynaptic profiles immunopositive for VGluT1 and VGluT2 in the neostriatum, and GluR4-immunoreactive particles were observed on postsynaptic and presynaptic profiles positive for VGluT1. Quantitative analysis revealed that 27,45% of GluR1-, GluR2-, GluR2/3- and GluR4-immunopositive particles found in VGluT1- or VGluT2-positive synaptic structures in the neostriatum were associated with the presynaptic profiles of VGluT-positive axons. In contrast, VGluT-positive presynaptic profiles in the neostriatum showed almost no immunoreactivity for NMDA receptor subunits NR1 or NR2A/B. Furthermore, almost no GluR2/3-immunopositive particles were observed in presynaptic profiles of VGluT3-positive (cholinergic) terminals that made asymmetric synapses in the neostriatum, or in those of VGluT1- or VGluT2-positive terminals in the neocortex. The present results indicate that AMPA receptor subunits but not NMDA receptor subunits are located on axon terminals of corticostriatal and thalamostriatal afferents, and suggest that glutamate released from these axon terminals controls the activity of the terminals through the presynaptic AMPA autoreceptors. [source] The subcellular localization of GABAB receptor subunits in the rat substantia nigraEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2003Justin Boyes Abstract The inhibitory effects of GABA within the substantia nigra (SN) are mediated in part by metabotropic GABAB receptors. To better understand the mechanisms underlying these effects, we have examined the subcellular localization of the GABAB receptor subunits, GABAB1 and GABAB2, in SN neurons and afferents using pre-embedding immunocytochemistry combined with anterograde or retrograde labelling. In both the SN pars compacta (SNc) and pars reticulata (SNr), GABAB1 and GABAB2 showed overlapping, but distinct, patterns of immunolabelling. GABAB1 was more strongly expressed by putative dopaminergic neurons in the SNc than by SNr projection neurons, whereas GABAB2 was mainly expressed in the neuropil of both regions. Immunogold labelling for GABAB1 and GABAB2 was localized in presynaptic and postsynaptic elements throughout the SN. The majority of labelling was intracellular or was associated with extrasynaptic sites on the plasma membrane. In addition, labelling for both subunits was found on the presynaptic and postsynaptic membranes at symmetric, putative GABAergic synapses, including those formed by anterogradely labelled striatonigral and pallidonigral terminals. Labelling was also observed on the presynaptic membrane and at the edge of the postsynaptic density at asymmetric, putative excitatory synapses. Double immunolabelling, using the vesicular glutamate transporter 2, revealed the glutamatergic nature of many of the immunogold-labelled asymmetric synapses. The widespread distribution of GABAB subunits in the SNc and SNr suggests that GABAB -mediated effects in these regions are likely to be more complex than previously described, involving presynaptic autoreceptors and heteroreceptors, and postsynaptic receptors on different populations of SN neurons. [source] Synaptic localization of GABAA receptor subunits in the substantia nigra of the rat: effects of quinolinic acid lesions of the striatumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2002Fumino Fujiyama Abstract The inhibitory amino acid, ,-aminobutyric acid (GABA), plays a critical role in the substantia nigra (SN) in health and disease. GABA transmission is controlled in part by the type(s) of GABA receptor expressed, their subunit composition and their location in relation to GABA release sites. In order to define the subcellular localization of GABAA receptors in the SN in normal and pathological conditions, sections of SN from control rats and rats that had received quinolinic acid lesions of the striatum were immunolabelled using the postembedding immunogold technique with antibodies against subunits of the GABAA receptor. Immunolabelling for ,1, ,2/3 and ,2 subunits was primarily located at symmetrical synapses. Double-labelling revealed that ,2/3 subunit-positive synapses were formed by terminals that were enriched in GABA. Colocalization of ,1, ,2/3 and ,2 subunits occurred at individual symmetrical synapses, some of which were identified as degenerating terminals derived from the striatum. In the SN ipsilateral to the striatal lesion there was a significant elevation of immunolabelling for ,2/3 subunits of the GABAA receptor at symmetrical synapses, but not of GluR2/3 subunits of the AMPA receptor at asymmetrical synapses. It was concluded that fast GABAA -mediated transmission occurs primarily at symmetrical synapses within the SN, that different receptor subunits coexist at individual synapses and that the upregulation of GABAA receptors following striatal lesions is expressed as increased receptor density at synapses. The upregulation of GABAA receptors in Huntington's disease and its models is thus likely to lead to an increased efficiency of transmission at intact GABAergic synapses in the SN and may partly underlie the motor abnormalities of this disorder. [source] NMDA receptor subunits GluR,1, GluR,3 and GluR,1 are enriched at the mossy fibre,granule cell synapse in the adult mouse cerebellumEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001Kazuyuki Yamada Abstract Cerebellar N -methyl- d -aspartate (NMDA) receptors are concentrated in the granular layer and are involved in motor coordination and the induction of long-term potentiation at mossy fibre,granule cell synapses. In the present study, we used immunohistochemistry to examine the distribution of NMDA receptor subunits in the adult mouse cerebellum. We found that appropriate pepsin pretreatment of sections greatly enhanced the sensitivity and specificity of immunohistochemical detection. As a result, intense immunolabelling for GluR,1 (NR2A), GluR,3 (NR2C), and GluR,1 (NR1) all appeared in synaptic glomeruli of the granular layer. Double immunofluorescence showed that these subunits were colocalized in individual synaptic glomeruli. Within the glomerulus, NMDA receptor subunits were located between centrally-located huge mossy fibre terminals and peripherally-located tiny Golgi axon terminals. By immunoelectron microscopy, all three subunits were detected at the postsynaptic junction in granule cell dendrites, forming synapses with mossy fibre terminals. Consistent with the known functional localization, GluR,1, GluR,3, and GluR,1 are, thus, anatomically concentrated at the mossy fibre,granule cell synapse. By contrast, immunohistochemical signals were very low in Purkinje cell somata and dendrites in the molecular layer. The lack of GluR,1 immunolabelling in Purkinje cells was unexpected because the cells express GluR,1 mRNA at high levels and high levels of GluR,1 protein in the molecular layer were revealed by immunoblot. As Purkinje cells are exceptionally lacking GluR, expression, the discrepant result may provide in vivo evidence suggesting the importance of accompanying GluR, subunits in synaptic localization of GluR,1. [source] Heterogeneous distribution of AMPA glutamate receptor subunits at the photoreceptor synapses of rodent retinaEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2001Iris Hack Abstract In the retina the segregation of different aspects of visual information starts at the first synapse in signal transfer from the photoreceptors to the second-order neurons, via the neurotransmitter glutamate. We examined the distribution of the four AMPA glutamate receptor subunits GluR1,GluR4 at the photoreceptor synapses in mouse and rat retinae by light and immunoelectron microscopy and serial section reconstructions. On the dendrites of OFF-cone bipolar cells, which make flat, noninvaginating contacts postsynaptic at cone synaptic terminals, the subunits GluR1 and GluR2 were predominantly found. Horizontal cell processes postsynaptic at both rod and cone synaptic terminals preferentially expressed the subunits GluR2, GluR2/3 and GluR4. An intriguing finding was the presence of GluR2/3 and GluR4 subunits on dendrites of putative rod bipolar cells, which are thought to signal through the sign-inverting metabotropic glutamate receptor 6, mGluR6. Furthermore, at the rod terminals, horizontal cell processes and rod bipolar cell dendrites showed labelling for the AMPA receptor subunits at the ribbon synaptic site or perisynaptically at their site of invagination into the rod terminal. The wide distribution of AMPA receptor subunits at the photoreceptor synapses suggests that AMPA receptors play an important role in visual signal transfer from the photoreceptors to their postsynaptic partners. [source] Distribution of glycine receptor subunits on primate retinal ganglion cells: a quantitative analysisEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2000Bin Lin Abstract This study investigates the distribution of inhibitory neurotransmitter receptors on sensory neurons. Ganglion cells in the retina of a New World monkey, the common marmoset Callithrix jacchus, were injected with Lucifer yellow and Neurobiotin and subsequently processed with antibodies against one (,1), or against all subunits, of the glycine receptor, or against the anchoring protein gephyrin. Immunoreactive (IR) puncta representing glycine receptor or gephyrin clusters were found on the proximal and the distal dendrites of all ganglion cell types investigated. For both parasol and midget cells, the density of receptor clusters was greater on distal than proximal dendrites for all antibodies tested. In parasol cells the average density for the ,1 subunit of the glycine receptor was 0.087 IR puncta/µm of dendrite, and for all subunits it was 0.119 IR puncta/µm of dendrite. Thus, the majority of glycine receptors on parasol cells contain the ,1 subunit. For parasol cells, we estimated an average of 1.5 glycinergic synapses/100 µm2 dendritic membrane on proximal dendrites and about 9.4 glycinergic synapses/100 µm2 on distal dendrites. The segregation of receptors to the distal dendrites appears to be a common feature of inhibitory neurotransmitter input to parasol and midget cells, and might be associated with the receptive field surround mechanism. [source] Gephyrin, a major postsynaptic protein of GABAergic synapsesEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000Marco Sassoč-Pognetto Abstract ,-aminobutyric acid type A (GABAA) receptors are located at the majority of inhibitory synapses in the mammalian brain. However, the mechanisms by which GABAA receptor subunits are targeted to, and clustered in, the postsynaptic membrane are poorly understood. Recent studies have demonstrated that gephyrin, a protein first identified as a component of the glycine receptor (GlyR) complex, is colocalized with several subtypes of GABAA receptors and is involved in the stabilization of postsynaptic GABAA receptor clusters. Thus, gephyrin functions as a clustering protein for major subtypes of inhibitory ion channel receptors. [source] | ||||||||||||||||||||||||||||