Search results for "Synapse"
showing 10 items of 243 documents
Brain choline has a typical precursor profile.
1998
Choline is product and precursor to both acetylcholine and membrane phospholipids, and, in the brain, is ultimately provided by the circulation. The brain is protected from excess choline and choline deprivation by a refined system of homeostatic mechanisms that maintain a level of extracellular choline that, for its role as precursor, meets saturation criteria under normal conditions. The kinetic and activity profiles of choline are typical for a biosynthetic precursor.
An exon junction complex‐independent function of Barentsz in neuromuscular synapse growth
2021
The exon junction complex controls the translation, degradation, and localization of spliced mRNAs, and three of its core subunits also play a role in splicing. Here, we show that a fourth subunit, Barentsz, has distinct functions within and separate from the exon junction complex in Drosophila neuromuscular development. The distribution of mitochondria in larval muscles requires Barentsz as well as other exon junction complex subunits and is not rescued by a Barentsz transgene in which residues required for binding to the core subunit eIF4AIII are mutated. In contrast, interactions with the exon junction complex are not required for Barentsz to promote the growth of neuromuscular synapses.…
Sparse Distributed Representation of Odors in a Large-scale Olfactory Bulb Circuit
2013
In the olfactory bulb, lateral inhibition mediated by granule cells has been suggested to modulate the timing of mitral cell firing, thereby shaping the representation of input odorants. Current experimental techniques, however, do not enable a clear study of how the mitral-granule cell network sculpts odor inputs to represent odor information spatially and temporally. To address this critical step in the neural basis of odor recognition, we built a biophysical network model of mitral and granule cells, corresponding to 1/100th of the real system in the rat, and used direct experimental imaging data of glomeruli activated by various odors. The model allows the systematic investigation and g…
Sequence Learning in a Single Trial: A Spiking Neurons Model Based on Hippocampal Circuitry.
2020
ABSTRACTIn contrast with our everyday experience using brain circuits, it can take a prohibitively long time to train a computational system to produce the correct sequence of outputs in the presence of a series of inputs. This suggests that something important is missing in the way in which models are trying to reproduce basic cognitive functions. In this work, we introduce a new neuronal network architecture that is able to learn, in a single trial, an arbitrary long sequence of any known objects. The key point of the model is the explicit use of mechanisms and circuitry observed in the hippocampus, which allow the model to reach a level of efficiency and accuracy that, to the best of our…
A modeling study suggesting how a reduction in the context-dependent input on CA1 pyramidal neurons could generate schizophrenic behavior.
2011
The neural mechanisms underlying schizophrenic behavior are unknown and very difficult to investigate experimentally, although a few experimental and modeling studies suggested possible causes for some of the typical psychotic symptoms related to this disease. The brain region most involved in these processes seems to be the hippocampus, because of its critical role in establishing memories for objects or events in the context in which they occur. In particular, a hypofunction of the N-methyl-D-aspartate (NMDA) component of the synaptic input on the distal dendrites of CA1 pyramidal neurons has been suggested to play an important role for the emergence of schizophrenic behavior. Modeling st…
Coincident glutamatergic depolarizations enhance GABAA receptor-dependent Cl- influx in mature and suppress Cl- efflux in immature neurons.
2021
The impact of GABAergic transmission on neuronal excitability depends on the Cl--gradient across membranes. However, the Cl--fluxes through GABAA receptors alter the intracellular Cl- concentration ([Cl-]i) and in turn attenuate GABAergic responses, a process termed ionic plasticity. Recently it has been shown that coincident glutamatergic inputs significantly affect ionic plasticity. Yet how the [Cl-]i changes depend on the properties of glutamatergic inputs and their spatiotemporal relation to GABAergic stimuli is unknown. To investigate this issue, we used compartmental biophysical models of Cl- dynamics simulating either a simple ball-and-stick topology or a reconstructed CA3 neuron. Th…
Synaptic release of zinc from brain slices: factors governing release, imaging, and accurate calculation of concentration.
2006
Cerebrocortical neurons that store and release zinc synaptically are widely recognized as critical in maintenance of cortical excitability and in certain forms of brain injury and disease. Through the last 20 years, this synaptic release has been observed directly or indirectly and reported in more than a score of publications from over a dozen laboratories in eight countries. However, the concentration of zinc released synaptically has not been established with final certainty. In the present work we have considered six aspects of the methods for studying release that can affect the magnitude of zinc release, the imaging of the release, and the calculated concentration of released zinc. We…
Separation of presynaptic Cav2 and Cav1 channel function in synaptic vesicle exo- and endocytosis by the membrane anchored Ca2+ pump PMCA
2021
Significance Synaptic vesicle (SV) release from presynaptic terminals requires nanometer precise control of action potential (AP)–triggered calcium influx through voltage-gated calcium channels (VGCCs). SV recycling also depends on calcium signals, though in different spatiotemporal domains. Mechanisms for separate control of SV release and recycling by AP-triggered calcium influx remain elusive. Here, we demonstrate largely independent regulation of release and recycling by two different populations of VGCCs (Cav2, Cav1), identify Cav1 as one of potentially multiple calcium entry routes for endocytosis regulation, and show functional separation of simultaneous calcium signals in the nanome…
Apical dendritic spines and axonic terminals in the bipyramidal neurons of the dorsomedial cortex of lizards (Lacerta).
1984
Gold-toned bipyramidal neurons of the dorsomedial cortex of Lacerta have been studied using light and electron microscopy. The spines have been classified as stubby, mushroom-shaped or thin. Thin and mushroom-shaped spines are only found on proximal and intermediate dendritic segments, whereas stubby spines are found on distal dendritic segments. A Timm's method modification for electron microscopy (sulphide-osmium procedure) has been used. Timm-positive axonal endings usually synapse on thin and mushroom-shaped spines, whereas Timm-negative axonal endings usually synapse on stubby spines. Timm-positive afferents and their post-synaptic spines on bipyramidal neurons of Lacerta's dorsomedial…
Plasticity of mouse enteric synapses mediated through endocannabinoid and purinergic signaling
2012
The myenteric and submucosal plexuses of the enteric nervous system (ENS) exist as interconnected integrative nerve networks within the wall of the gastrointestinal (GI) tract. Activity of the ENS is responsible for the control of the digestive and protective functions of the gut.1 Synaptic transmission between enteric neurons propagates information from intrinsic afferent neurons to interneurons, and then from interneurons to motor neurons that control final effectors such as smooth muscle and the secretory epithelium. Acetylcholine (ACh) is the major excitatory neurotransmitter in the myenteric plexus, acting on nicotinic receptors at synapses between neurons and on muscarinic receptors a…