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Synaptic Development (synaptic + development)

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Life Sciences	80%

Selected Abstracts

Myopodia (postsynaptic filopodia) participate in synaptic target recognition

DEVELOPMENTAL NEUROBIOLOGY, Issue 1 2003
Sarah Ritzenthaler
Abstract Synaptic partner cells recognize one another by utilizing a variety of molecular cues. Prior to neuromuscular synapse formation, Drosophila embryonic muscles extend dynamic actin-based filopodia called "myopodia." In wild-type animals, myopodia are initially extended randomly from the muscle surface but become gradually restricted to the site of motoneuron innervation, a spatial redistribution we call "clustering." Previous experiments with prospero mutant embryos demonstrated that myopodia clustering does not occur in the absence of motoneuron outgrowth into the muscle field. However, whether myopodia clustering is due to a general signal from passing axons or is a result of the specific interactions between synaptic partners remained to be investigated. Here, we have examined the relationship of myopodia to the specific events of synaptic target recognition, the stable adhesion of synaptic partners. We manipulated the embryonic expression of ,PS2 integrin and Toll, molecules known to affect synaptic development, to specifically alter synaptic targeting on identified muscles. Then, we used a vital single-cell labeling approach to visualize the behavior of myopodia in these animals. We demonstrate a strong positive correlation between myopodia activity and synaptic target recognition. The frequency of myopodia clustering is lowered in cases where synaptic targeting is disrupted. Myopodia clustering seems to result from the adherence of a subset of myopodia to the innervating growth cone while the rest are eliminated. The data suggest that postsynaptic cells play a dynamic role in the process of synaptic target recognition. © 2003 Wiley Periodicals, Inc. J Neurobiol 55: 31,40, 2003 [source]

Impact of basic FGF expression in astrocytes on dopamine neuron synaptic function and development

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2006
Caroline Forget
Abstract Behavioural sensitization to amphetamine (AMPH) requires action of the drug in the ventral midbrain where dopamine (DA) neurons are located. In vivo studies suggest that AMPH sensitization requires enhanced expression of basic fibroblast growth factor (bFGF) in the nucleus of midbrain astrocytes. One idea is that the AMPH-induced increase in bFGF expression in astrocytes leads to enhanced secretion of this peptide and to long-term plasticity in DA neurons. To study directly the effects of astrocytic expression of bFGF on DA neurons, we established a cell-culture model of mesencephalic astrocytes and DA neurons. Immunolabelling showed that even in the absence of a pharmacological stimulus, the majority of mesencephalic astrocytes in culture express bFGF at a nuclear level. Arguing against the idea that bFGF was secreted, bFGF was undetectable in the extracellular medium (below 10 pg/mL). However, supplementing culture medium with exogenous bFGF at standard concentrations (20 ng/mL) led to a dramatic change in the morphology of astrocytes, increased spontaneous DA release, and inhibited synapse formation by individual DA neurons. RNA interference (siRNA) against bFGF mRNA, caused a reduction in DA release but produced no change in synaptic development. Together these data demonstrate that under basal conditions (in the absence of a pharmacological stimulus such as amphetamine) bFGF is not secreted even though there is abundant nuclear expression in astrocytes. The effects of bFGF seen here on DA neurons are thus likely to be mediated through more indirect glial,neuronal interactions, leading to enhanced DA release without a necessary change in synapse number. [source]

In vivo quantitative proton MRSI study of brain development from childhood to adolescence,

JOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 2 2002
Alena Horská PhD
Abstract Purpose To quantify regional variations in metabolite levels in the developing brain using quantitative proton MR spectroscopic imaging (MRSI). Materials and Methods Fifteen healthy subjects three to 19 years old were examined by in vivo multislice proton MRSI. Concentrations of N-acetyl aspartate (NAA), total choline (Cho), total creatine (Cr), and peak area ratios were determined in selected frontal and parietal gray and white matter regions, basal ganglia, and thalamus. Results In cortical gray matter regions, the ratio of NAA/Cho increased to a maximum at 10 years and decreased thereafter (P = 0.010). In contrast, in white matter, average ratios NAA/Cho increased linearly with age (P = 0.045). In individual brain regions, age-related changes in NAA/Cho were found in the putamen (P = 0.044). No significant age-related changes in NAA, Cho, Cr, or other metabolite ratios could be determined. Conclusion Consistent with recent studies using other structural and functional neuroimaging techniques, our data suggest that small but significant changes occur in regional cerebral metabolism during childhood and adolescence. Non-linear age related changes of NAA/Cho in frontal and parietal areas, resembling previously reported age related changes in rates of glucose utilization and cortical volumes, may be associated with dendritic and synaptic development and regression. Linear age-related changes of NAA/Cho in white matter are also in agreement with age-related increases in white matter volumes, and may reflect progressive increases in axonal diameter and myelination. J. Magn. Reson. Imaging 2002;15:137,143. Published 2002 Wiley-Liss, Inc. [source]

Visual deprivation increases accumulation of dense core vesicles in developing optic tectal synapses in Xenopus laevis

THE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 12 2010
Jianli Li
Abstract Despite considerable progress in understanding the molecular components of synapses in the central nervous system, the ultrastructural rearrangements underlying synaptic development remain unclear. We used serial section transmission electron microscopy and three-dimensional reconstructions of the optic tectal neuropil of Xenopus laevis tadpoles to detect and quantify changes in synaptic ultrastructure over a 1-week period from stages 39 and 47, during which time the visual system of Xenopus tadpoles becomes functional. Synapse density, presynaptic maturation index, and number of synapses per axon bouton increase, whereas the number of DCVs per bouton decreases, between stages 39 and 47. The width of the synaptic cleft decreased and the diameter of postsynaptic profiles increased between stages 39 and 47 and then remained relatively unchanged after stage 47. We found no significant difference in synapse maturation between GABAergic and non-GABAergic synapses. To test the effect of visual experience on synaptogenesis, animals were deprived of visual experience for 3 days from stage 42 to 47. Visual deprivation decreased synapse maturation and the number of connections per bouton. Furthermore, visual deprivation increased the number of DCVs per bouton by more than twofold. The visual-deprivation-induced decrease in synaptic connections is specific to asymmetric non-GABAergic synapses; however, both symmetric GABAergic and asymmetric synapses show comparable increases in the number DCVs with visual deprivation. In both the control and the visually deprived animals, the number of DCVs per bouton is highly variable and does not correlate with either synapse maturation or the number of connected partners per bouton. These data suggest that synaptogenesis and DCV accumulation are regulated by visual experience and further suggest a complex spatial and temporal relation between DCV accumulation and synapse formation. J. Comp. Neurol. 518:2365,2381, 2010. © 2010 Wiley-Liss, Inc. [source]

Impaired development of hippocampal mossy fibre synapses in mouse mutants for the presynaptic scaffold protein Bassoon

THE JOURNAL OF PHYSIOLOGY, Issue 12 2010
Frederic Lanore
Bassoon, a protein highly concentrated at the synaptic active zone, is thought to participate in the organization of the cytomatrix at the site of neurotransmitter release. Bassoon is amongst the first proteins to accumulate at newly formed synaptic junctions, raising the question of the functional role of this protein in the early stages of synaptic development. Here we show that the course of synaptic maturation of hippocampal mossy fibre (MF) synapses (glutamatergic synapses with multiple release sites) is markedly altered during the first 2 weeks of postnatal development in mutant mice lacking the central region of Bassoon (Bsn,/, mice). At postnatal day 7 (P7), Bsn,/, mice display large amplitude MF-EPSCs with decreased paired pulse ratios, an abnormality which may be linked to deficits in the organization of the presynaptic active zone. Surprisingly, 1 week later, decreased MF-EPSCs amplitude is observed in Bsn,/, mice, consistent with the inactivation of a subset of synaptic release sites. Finally, at more mature states a decreased posttetanic potentiation is observed at MF-synapses. These results support the notion that Bassoon is important for organizing the presynaptic active zone during the postnatal maturation of glutamatergic synapses. [source]