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Candido Lopezgarcia - One of the best experts on this subject based on the ideXlab platform.
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Neurons of the medial cortex outer plexiform layer of the lizard podarcis hispanica golgi and immunocytochemical studies
The Journal of Comparative Neurology, 1994Co-Authors: J A L De La Iglesia, Francisco Jose Martinezguijarro, Candido LopezgarciaAbstract:The study of Golgi-impregnated lizard brains has revealed a scarce but heterogeneous Neuronal population in the outer plexiform layer of the medial cortex. Some of the Neuronal types detected here resemble the Neurons of the dentate molecular layer of the mammalian hippocampus. According to their morphology, five intrinsic Neuronal types have been clearly identified: short axon aspinous Bipolar Neuron (type 1, or sarmentous Neuron), short axon aspinous juxtasomatic Neuron (type 2, or coral Neuron), short axon sparsely spinous multipolar Neuron (type 3, or stellate Neuron), short axon sparsely spinous juxtasomatic multipolar Neuron (type 4, or deep stellate Neuron, and sparsely spinous juxtasomatic horizontal Neuron (type 5, or couchant Neuron). Most Neuronal types were identified as γ-aminobutyric acid (GABA) and parvalbumin immunoreactive, and are thus probably involved in medial cortex inhibition. Moreover, a small fraction of them displayed s-endorphin immunoreactivity. The distribution of these Neuronal types is not uniform in the laminae of the outer plexiform layer. Type 1 (sarmentous) and type 3 (stellate) Neurons overlap the axonal field projection coming from the dorsal cortex and the thalamus, whereas types 4 (deep stellate) and 5 (couchant) Neurons overlap ipsi- and contralateral dorsomedial projection fields as well as raphe serotoninergic and opioid immunoreactive axonal plexi. Thus, these Neuronal types may be involved in the control of specific inputs to the medial cortex by presumably feed-forward inhibition; nevertheless, feed-back inhibition may also occur regarding type 4 (deep stellate) Neurons that extend deep dendrites to the zinc-rich bouton field.
Richard H Masland - One of the best experts on this subject based on the ideXlab platform.
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neuroscience accurate maps of visual circuitry
Nature, 2013Co-Authors: Richard H MaslandAbstract:Such is the brain's complexity that even small neural circuits contain hundreds of Neurons making thousands of connections. Connectivity and optical analyses provide close-up views of two such circuits. See Articles p.168 , p.175 & Letter p.212 Three papers in this issue of Nature use the retina as a model for mapping Neuronal circuits from the level of individual synaptic contacts to the long-range scale of dendritic interactions. Helmstaedter et al. used electron microscopy to map a mammalian retinal circuit of close to a thousand Neurons. The work reveals a new type of retinal Bipolar Neuron and suggests functional mechanisms for known visual computations. The other two groups study the detection of visual motion in the Drosophila visual system — a classic neural computation model. Takemura et al. used semi-automated electron microscopy to reconstruct the basic connectome (8,637 chemical synapses among 379 Neurons) of Drosophila's optic medulla. Their results reveal a candidate motion detection circuit with a wiring plan consistent with direction selectivity. Maisak et al. used calcium imaging to show that T4 and T5 Neurons are divided into specific subpopulations responding to motion in four cardinal directions, and are specific to 'ON' versus 'OFF' edges, respectively.
Proleta Datta - One of the best experts on this subject based on the ideXlab platform.
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THE FUNCTIONAL ORGANIZATION OF SYNAPTIC VESICLE POOLS IN A RETINAL Bipolar Neuron
2012Co-Authors: Proleta DattaAbstract:v TABLE OF CONTENTS vii LIST OF FIGURES viii LIST OF TABLES x CHAPTER I – GENERAL INTRODUCTION 1 CHAPTER II – GENERAL METHODS 18 CHAPTER III – RELATIONSHIP BETWEEN VESICLE POOLS 26 INTRODUCTION 27 RESULTS 36 DISCUSSION 53 CHAPTER IV – VESICLE POOLS IN SNARE COMPLEX 59 INTRODUCTION 60 RESULTS 67 DISCUSSION 92 CHAPTER V – CONCLUSIONS AND FUTURE DIRECTIONS 104 APPENDIX A 117 APPENDIX B 118 REFERENCES 124 VITA 168 viii LIST OF FIGURES Fig 1.1 The classical synaptic vesicle cycle 5 Fig 1.2 Ultra structure of Retinal ribbon synapses 14 Fig 2.1 Isolated Mb1 Neuron and terminal 20 Fig 3.1 Location and size of vesicle pools of the goldfish Bipolar cell 31 Fig 3.2 Protocol used for the train stimulus 36 Fig 3.3 Sample trace from a terminal stimulated with a pulse train. 37 Fig 3.4 A pulse train stimuli reveals fusion of multiple vesicle pools. 38 Fig 3.5 The ATP sensitive component. 41 Fig 3.6 ATP is required for the refilling of the releasable and rapid pool. 43 Fig 3.7 Depletion of the releasable pool also depletes the rapid pool 46 Fig 3.8 Depletion of the releasable pool also depletes the rapid pool 47 Fig 3.9 The rapid pool is a subset of the releasable pool 50 Fig 3.10 The rapid pool is a subset of and draws from the releasable pool 51 Fig 3.11 Changes in intracellular calcium during experiment 4 53 Fig 4.1 Syntaxin 3B and scrambled peptides 67 Fig 4.2 Syntaxin 3 peptide prevents formation of the SNARE complex 68 Fig 4.3 Dialysis of the FITC tagged peptides were verified by increase in fluorescence 70 Fig 4.4 A SNARE complex inhibiting peptide blocks fusion of the reserve vesicle but not the releasable pool of vesicles 72 Fig 4.5 The Syntaxin peptide does not affect the number of vesicles in the releasable pool 73 Fig 4.6 The Syntaxin peptide does not affect fusion from the rapid pool 75
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SNARE Complex Assembly in Retinal Bipolar Neuron Exocytosis
Biophysical Journal, 2010Co-Authors: Proleta Datta, Leigh Beth Curtis, Roger Janz, Ruth HeidelbergerAbstract:Three kinetic components of exocytosis have been described in retinal Bipolar Neurons. They are thought to reflect the fusion of a docked pool of ribbon-tethered synaptic vesicles termed the rapid pool, the releasable pool of ribbon-tethered vesicles, and a cytoplasmic reserve pool. In Neurons, assembly of SNARE proteins facilitates exocytosis. We asked whether these pools could be distinguished on the basis of SNARE complex formation. Syntaxin3B is a t-SNARE in ribbon synapses. We generated a fluorescent peptide based on the syntaxin3B SNARE binding motif from goldfish. The peptide was dialyzed into isolated synaptic terminals of goldfish retinal Bipolar cells via a whole-terminal recording electrode. A scrambled peptide served as control. Exocytosis was monitored with membrane capacitance measurements. Beginning one minute after break-in, a 1s stimulation, sufficient to deplete the releasable pool, was given every 60 seconds. The first exocytotic response was not significantly altered by the syntaxin3B peptide. However, by the fourth pulse, the exocytotic response in terminals dialyzed with the syntaxin3B peptide was reduced by 89% relative to the first, whereas that with the control peptide was reduced by only 45% (p < 0.04). This effect was not due to a reduction in calcium influx. Next, we implemented a pulse train protocol that captures the three components of release. Control terminals showed both depletion and replenishment of the pools. Terminals dialyzed with the syntaxin3B peptide showed: 1) immediate loss of the exocytotic component attributed to the reserve pool 2) decreased refilling of the rapid and releasable pools. The results demonstrate that reserve pool vesicles are unlike those in the rapid and releasable pools. It is likely that pool refilling is inhibited by the syntaxin3B peptide because reserve vesicles establish new SNARE complexes when they join a fusion-competent vesicle pool.
Ruth Heidelberger - One of the best experts on this subject based on the ideXlab platform.
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SNARE Complex Assembly in Retinal Bipolar Neuron Exocytosis
Biophysical Journal, 2010Co-Authors: Proleta Datta, Leigh Beth Curtis, Roger Janz, Ruth HeidelbergerAbstract:Three kinetic components of exocytosis have been described in retinal Bipolar Neurons. They are thought to reflect the fusion of a docked pool of ribbon-tethered synaptic vesicles termed the rapid pool, the releasable pool of ribbon-tethered vesicles, and a cytoplasmic reserve pool. In Neurons, assembly of SNARE proteins facilitates exocytosis. We asked whether these pools could be distinguished on the basis of SNARE complex formation. Syntaxin3B is a t-SNARE in ribbon synapses. We generated a fluorescent peptide based on the syntaxin3B SNARE binding motif from goldfish. The peptide was dialyzed into isolated synaptic terminals of goldfish retinal Bipolar cells via a whole-terminal recording electrode. A scrambled peptide served as control. Exocytosis was monitored with membrane capacitance measurements. Beginning one minute after break-in, a 1s stimulation, sufficient to deplete the releasable pool, was given every 60 seconds. The first exocytotic response was not significantly altered by the syntaxin3B peptide. However, by the fourth pulse, the exocytotic response in terminals dialyzed with the syntaxin3B peptide was reduced by 89% relative to the first, whereas that with the control peptide was reduced by only 45% (p < 0.04). This effect was not due to a reduction in calcium influx. Next, we implemented a pulse train protocol that captures the three components of release. Control terminals showed both depletion and replenishment of the pools. Terminals dialyzed with the syntaxin3B peptide showed: 1) immediate loss of the exocytotic component attributed to the reserve pool 2) decreased refilling of the rapid and releasable pools. The results demonstrate that reserve pool vesicles are unlike those in the rapid and releasable pools. It is likely that pool refilling is inhibited by the syntaxin3B peptide because reserve vesicles establish new SNARE complexes when they join a fusion-competent vesicle pool.
Winfried Denk - One of the best experts on this subject based on the ideXlab platform.
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Connectomic reconstruction of the inner plexiform layer in the mouse retina
Nature, 2013Co-Authors: Moritz Helmstaedter, Kevin L. Briggman, Srinivas C. Turaga, Viren Jain, H. Sebastian Seung, Winfried DenkAbstract:Improved electron microscopy methods are used to map a mammalian retinal circuit of close to 1,000 Neurons; the work reveals a new type of retinal Bipolar Neuron and suggests functional mechanisms for known visual computations. Three papers in this issue of Nature use the retina as a model for mapping Neuronal circuits from the level of individual synaptic contacts to the long-range scale of dendritic interactions. Helmstaedter et al . used electron microscopy to map a mammalian retinal circuit of close to a thousand Neurons. The work reveals a new type of retinal Bipolar Neuron and suggests functional mechanisms for known visual computations. The other two groups study the detection of visual motion in the Drosophila visual system — a classic neural computation model. Takemura et al . used semi-automated electron microscopy to reconstruct the basic connectome (8,637 chemical synapses among 379 Neurons) of Drosophila 's optic medulla. Their results reveal a candidate motion detection circuit with a wiring plan consistent with direction selectivity. Maisak et al . used calcium imaging to show that T4 and T5 Neurons are divided into specific subpopulations responding to motion in four cardinal directions, and are specific to 'ON' versus 'OFF' edges, respectively. Comprehensive high-resolution structural maps are central to functional exploration and understanding in biology. For the nervous system, in which high resolution and large spatial extent are both needed, such maps are scarce as they challenge data acquisition and analysis capabilities. Here we present for the mouse inner plexiform layer—the main computational neuropil region in the mammalian retina—the dense reconstruction of 950 Neurons and their mutual contacts. This was achieved by applying a combination of crowd-sourced manual annotation and machine-learning-based volume segmentation to serial block-face electron microscopy data. We characterize a new type of retinal Bipolar interNeuron and show that we can subdivide a known type based on connectivity. Circuit motifs that emerge from our data indicate a functional mechanism for a known cellular response in a ganglion cell that detects localized motion, and predict that another ganglion cell is motion sensitive.