Tonic transmitter release in a graded potential synapse

Uusitalo, R. O.; Juusola, Mikko; Kouvalainen, E.; Weckström, Matti

doi:10.1152/jn.1995.74.1.470

Cited by 29 publications

(37 citation statements)

References 21 publications

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“…These show a rather dramatic effect just after the light to dark transition. It seems that synaptic transmission is completely shut down when the photoreceptor hyperpolarizes, and bounces back about 15 ms later, very similar to results reported by Uusitalo et al (1995). This is confirmed by the standard deviation of the fluctuation waveforms shown in panel E. The fluctuations during constant light, say from 20-100 ms and from 130-200 ms, are due to a combination of photoreceptor noise amplified by the synapse and intrinsic noise of the vesicle release itself.…”

Section: Efficiency and Adaptation Of The Photoreceptor-lmc Synapsesupporting

confidence: 85%

Timing and Counting Precision in the Blowfly Visual System

Ruyter¹,

Bialek

2002

Models of Neural Networks IV

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We measure the reliability of signals at three levels within the blowfly visual system, and present a theoretical framework for analyzing the experimental results, starting from the Poisson process. We find that blowfly photoreceptors, up to frequencies of 50-100 Hz and photon capture rates of up to about 3 · 10 5 /s, operate well within an order of magnitude from ideal photon counters. Photoreceptors signals are transmitted to LMCs through an array of chemical synapses. We quantify a lower bound on LMC reliability, which in turn provides a lower bound on synaptic vesicle release rate, assuming Poisson statistics. This bound is much higher than what is found in published direct measurements of vesicle release rates in goldfish bipolar cells, suggesting that release statistics may be significantly sub-Poisson. Finally we study H1, a motion sensitive tangential cell in the fly's lobula plate, which transmits information about a continuous signal by sequences of action potentials. In an experiment with naturalistic motion stimuli performed on a sunny day outside in the field, H1 transmits information at about 50% coding efficiency down to millisecond spike timing precision. Comparing the measured reliability of H1's response to motion steps with the bounds on the accuracy of motion computation set by photoreceptor noise, we find that the fly's brain makes efficient use of the information available in the photoreceptor array.

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Section: Efficiency and Adaptation Of The Photoreceptor-lmc Synapsesupporting

confidence: 85%

Timing and Counting Precision in the Blowfly Visual System

Ruyter¹,

Bialek

2002

Models of Neural Networks IV

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“…For the used LMCs, the resting potentials were ϽϪ30 mV and maximum responses Ͼ15 mV (WT Canton-S, all mutants and controls). In Calliphora lamina, L1 and L2 generate similar responses, while the responses of L3 are more hyperpolarized, showing the largest off-transients (Uusitalo et al, 1995b). In Drosophila, we have not identified different LMC subtypes, but as L1 and L2 occupy the largest volume most recordings were probably in them.…”

Section: Generation Of Dskmentioning

confidence: 64%

“…10). Darkening hyperpolarizes photoreceptors, reducing their tonic histamine release (Uusitalo et al, 1995b;Zheng et al, 2006). This in turn depolarizes LMCs/ACs, increasing their feedbacks to photoreceptor axons (Zheng et al, 2006).…”

Section: Homeostatic Sensitivity Regulationmentioning

confidence: 99%

TheDrosophilaSK Channel (dSK) Contributes to Photoreceptor Performance by Mediating Sensitivity Control at the First Visual Network

Tayoun

Li²,

Chu³

et al. 2011

J. Neurosci.

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The contribution of the SK (small-conductance calcium-activated potassium) channel to neuronal functions in complex circuits underlying sensory processing and behavior is largely unknown in the absence of suitable animal models. Here, we generated a Drosophila line that lacks the single highly conserved SK gene in its genome (dSK). In R1-R6 photoreceptors, dSK encodes a slow Ca 2ϩ -activated K ϩ current similar to its mammalian counterparts. Compared with wild-type, dSK Ϫ photoreceptors and interneurons showed accelerated oscillatory responses and adaptation. These enhanced kinetics were accompanied with more depolarized dSK Ϫ photoreceptors axons, assigning a role for dSK in network gain control during light-to-dark transitions. However, compensatory network adaptation, through increasing activity between synaptic neighbors, overcame many detriments of missing dSK current enabling dSK Ϫ photoreceptors to maintain normal information transfer rates to naturalistic stimuli. While demonstrating important functional roles for dSK channel in the visual circuitry, these results also clarify how homeostatically balanced network functions can compensate missing or faulty ion channels.

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“…At least in the photoreceptors of the giant barnacle, the rate of histamine synthesis is slow (Morgan et al, 1999). One can, therefore, readily predict that, associated with the high output of transmitter from photoreceptor terminals, even in the dark (Uusitalo et al, 1995), the mechanisms for histamine recycling in arthropod visual systems are highly advanced. Histamine reuptake, for example, acts with high efficiency in flies (Melzig et al, 1998).…”

Section: Distribution Of Ebony Expression In the Optic Lobes Localizementioning

confidence: 99%

Ebony protein in the Drosophila nervous system: Optic neuropile expression in glial cells

Richardt

Rybak

Störtkuhl

et al. 2002

J of Comparative Neurology

112

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The Drosophila ebony mutation (Bridges and Morgan, [1923] Publs Carnegie Inst Wash 327:50) reveals a pleiotropic phenotype with cuticular and behavioral defects. To understand Ebony function in the nervous system, particularly in transmission of the visual signal, it is essential to know the cell type and temporal characteristics of its expression throughout development. Therefore, we raised an antiserum against an Ebony peptide to detect the protein in whole-mount and slice preparations of Drosophila. Attention was focused on ebony expression in the adult optic neuropiles of the fly. Colocalization of Ebony with neuronal or glial cell markers in frozen sections showed non-neuronal expression of ebony in the lamina and medulla neuropiles. Furthermore, colocalization with glial cell markers demonstrated glial expression of ebony in epithelial glia of the lamina and neuropile glia of the distal medulla. This finding was confirmed for the lamina epithelial glia by electron microscopic examination of immunolabeling by using the diaminobenzidine method. These glia have in common that they match the two sites of histamine release from the compound eye's photoreceptors. Possible ways in which the biochemical activity of Ebony might function with respect to histamine release are considered.

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Tonic transmitter release in a graded potential synapse

Cited by 29 publications

References 21 publications

Timing and Counting Precision in the Blowfly Visual System

Timing and Counting Precision in the Blowfly Visual System

TheDrosophilaSK Channel (dSK) Contributes to Photoreceptor Performance by Mediating Sensitivity Control at the First Visual Network

Ebony protein in the Drosophila nervous system: Optic neuropile expression in glial cells

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