The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Annette Zippelius - One of the best experts on this subject based on the ideXlab platform.
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Biophysical model of a single Synaptic Connection: Transmission properties are determined by the cooperation of pre- and postSynaptic mechanisms
Neurocomputing, 2001Co-Authors: Julia Trommershäuser, Annette ZippeliusAbstract:Abstract A stochastic model of Synaptic transmission has been designed on the basis of electrophysiological experiments. The model includes preSynaptic mechanisms of recruitment and calcium related release of vesicles, transmitter dynamics in the cleft and postSynaptic receptor kinetics. Monte Carlo simulations of a single Synaptic Connection are performed and demonstrate that synapses depress during repetitive preSynaptic stimulation due to depletion of preSynaptic vesicles as well as receptor desensitization. Only for stimulation frequencies below 40 Hz depression is caused solely preSynaptically by depletion of vesicles. It is shown that specific physiological conditions determine the frequency dependence of steady state depression currents and set limits on the range of possibly rate-coded transmission.
James J. Hickman - One of the best experts on this subject based on the ideXlab platform.
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Tissue engineering the monoSynaptic circuit of the stretch reflex arc with co-culture of embryonic motoneurons and proprioceptive sensory neurons
Biomaterials, 2012Co-Authors: Xiufang Guo, Jennifer E. Ayala, Mercedes Gonzalez, Maria Stancescu, Stephen Lambert, James J. HickmanAbstract:The sensory circuit of the stretch reflex arc is composed of intrafusal muscle fibers and their innervating proprioceptive neurons that convert mechanical information regarding muscle length and tension into action potentials that synapse onto the homonymous motoneurons in the ventral spinal cord which innervate the extrafusal fibers of the same muscle. To date, the in vitro Synaptic Connection between proprioceptive sensory neurons and spinal motoneurons has not been demonstrated. A functional in vitro system demonstrating this Connection would enable the understanding of feedback by the integration of sensory input into the spinal reflex arc. Here we report a co-culture of rat embryonic motoneurons and proprioceptive sensory neurons from dorsal root ganglia (DRG) in a defined serum-free medium on a synthetic silane substrate (DETA). Furthermore, we have demonstrated functional synapse formation in the co-culture by immunocytochemistry and electrophysiological analysis. This work will be valuable for enabling in vitro model systems for the study of spinal motor control and related pathologies such as spinal cord injury, muscular dystrophy and spasticity by improving our understanding of the integration of the mechanosensitive feedback mechanism.
Dirk Feldmeyer - One of the best experts on this subject based on the ideXlab platform.
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cholinergic and adenosinergic modulation of Synaptic release
Neuroscience, 2020Co-Authors: Danqing Yang, Guanxiao Qi, Chao Ding, Dirk FeldmeyerAbstract:Abstract In this review we will discuss the effect of two neuromodulatory transmitters, acetylcholine (ACh) and adenosine, on the Synaptic release probability and short-term Synaptic plasticity. ACh and adenosine differ fundamentally in the way they are released into the extracellular space. ACh is released mostly from Synaptic terminals and axonal bouton of cholinergic neurons in the basal forebrain. Its mode of action on Synaptic release probability is complex because it activate both ligand-gated ion channels, so-called nicotinic ACh receptors and G-protein coupled muscarinic ACh receptors. In contrast, adenosine is released from both neurons and glia via nucleoside transporters or diffusion over the cell membrane in a non-vesicular, non-Synaptic fashion; its receptors are exclusively G-protein coupled receptors. We show that ACh and adenosine effects are highly specific for an identified Synaptic Connection and depend mostly on the preSynaptic but also on the postSynaptic receptor type and discuss the functional implications of these differences.
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high probability uniquantal transmission at excitatory synapses in barrel cortex
Science, 2003Co-Authors: Angus R Silver, Bert Sakmann, Joachim H R Lubke, Dirk FeldmeyerAbstract:The number of vesicles released at excitatory synapses and the number of release sites per Synaptic Connection are key determinants of information processing in the cortex, yet they remain uncertain. Here we show that the number of functional release sites and the number of anatomically identified Synaptic contacts are equal at Connections between spiny stellate and pyramidal cells in rat barrel cortex. Moreover, our results indicate that the amount of transmitter released per Synaptic contact is independent of release probability and the intrinsic release probability is high. These properties suggest that Connections between layer 4 and layer 2/3 are tuned for reliable transmission of spatially distributed, timing-based signals.
Naoko Kajimura - One of the best experts on this subject based on the ideXlab platform.
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lrit1 a retinal transmembrane protein regulates selective synapse formation in cone photoreceptor cells and visual acuity
Cell Reports, 2018Co-Authors: Akiko Ueno, Yoshihiro Omori, Yuko Sugita, Satoshi Watanabe, Taro Chaya, Takashi Kozuka, Satoyo Yoshida, Kenji Matsushita, Ryusuke Kuwahara, Naoko KajimuraAbstract:Summary In the vertebrate retina, cone photoreceptors play crucial roles in photopic vision by transmitting light-evoked signals to ON- and/or OFF-bipolar cells. However, the mechanisms underlying selective synapse formation in the cone photoreceptor pathway remain poorly understood. Here, we found that Lrit1, a leucine-rich transmembrane protein, localizes to the photoreceptor Synaptic terminal and regulates the Synaptic Connection between cone photoreceptors and cone ON-bipolar cells. Lrit1 -deficient retinas exhibit an aberrant morphology of cone photoreceptor pedicles, as well as an impairment of signal transmission from cone photoreceptors to cone ON-bipolar cells. Furthermore, we demonstrated that Lrit1 interacts with Frmpd2, a photoreceptor scaffold protein, and with mGluR6, an ON-bipolar cell-specific glutamate receptor. Additionally, Lrit1- null mice showed visual acuity impairments in their optokinetic responses. These results suggest that the Frmpd2-Lrit1-mGluR6 axis regulates selective synapse formation in cone photoreceptors and is essential for normal visual function.
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preSynaptic dystroglycan pikachurin complex regulates the proper Synaptic Connection between retinal photoreceptor and bipolar cells
The Journal of Neuroscience, 2012Co-Authors: Yoshihiro Omori, Taro Chaya, Naoko Kajimura, Fumiyuki Araki, Shoichi Irie, Koji Terada, Yuki Muranishi, Toshinori Tsujii, Shinji Ueno, Toshiyuki KoyasuAbstract:Dystroglycan (DG) is a key component of the dystrophin-glycoprotein complex (DGC) at the neuromuscular junction postsynapse. In the mouse retina, the DGC is localized at the presynapse of photoreceptor cells, however, the function of preSynaptic DGC is poorly understood. Here, we developed and analyzed retinal photoreceptor-specific DG conditional knock-out (DG CKO) mice. We found that the DG CKO retina showed a reduced amplitude and a prolonged implicit time of the ERG b-wave. Electron microscopic analysis revealed that bipolar dendrite invagination into the photoreceptor terminus is perturbed in the DG CKO retina. In the DG CKO retina, pikachurin, a DG ligand in the retina, is markedly decreased at photoreceptor synapses. Interestingly, in the Pikachurin(-/-) retina, the DG signal at the ribbon Synaptic terminus was severely reduced, suggesting that pikachurin is required for the preSynaptic accumulation of DG at the photoreceptor Synaptic terminus, and conversely DG is required for pikachurin accumulation. Furthermore, we found that overexpression of pikachurin induces formation and clustering of a DG-pikachurin complex on the cell surface. The Laminin G repeats of pikachurin, which are critical for its oligomerization and interaction with DG, were essential for the clustering of the DG-pikachurin complex as well. These results suggest that oligomerization of pikachurin and its interaction with DG causes DG assembly on the synapse surface of the photoreceptor Synaptic terminals. Our results reveal that the preSynaptic interaction of pikachurin with DG at photoreceptor terminals is essential for both the formation of proper photoreceptor ribbon Synaptic structures and normal retinal electrophysiology.
Julia Trommershäuser - One of the best experts on this subject based on the ideXlab platform.
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Biophysical model of a single Synaptic Connection: Transmission properties are determined by the cooperation of pre- and postSynaptic mechanisms
Neurocomputing, 2001Co-Authors: Julia Trommershäuser, Annette ZippeliusAbstract:Abstract A stochastic model of Synaptic transmission has been designed on the basis of electrophysiological experiments. The model includes preSynaptic mechanisms of recruitment and calcium related release of vesicles, transmitter dynamics in the cleft and postSynaptic receptor kinetics. Monte Carlo simulations of a single Synaptic Connection are performed and demonstrate that synapses depress during repetitive preSynaptic stimulation due to depletion of preSynaptic vesicles as well as receptor desensitization. Only for stimulation frequencies below 40 Hz depression is caused solely preSynaptically by depletion of vesicles. It is shown that specific physiological conditions determine the frequency dependence of steady state depression currents and set limits on the range of possibly rate-coded transmission.
