A dark decrement for enhanced dynamic sensitivity of retinal photoreceptors
| Autor: | Matthew A. Kreitzer, Shen Hu, Richard L. Chappell, Ivan A. Anastassov, Malcolm M. Slaughter |
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| Rok vydání: | 2021 |
| Předmět: |
Light
genetic structures Synaptic cleft chemistry.chemical_element Dark Adaptation Adaptation (eye) Zinc Retina 050105 experimental psychology 03 medical and health sciences 0302 clinical medicine Electroretinography medicine Photoreceptor Cells 0501 psychology and cognitive sciences Histidine Voltage-dependent calcium channel 05 social sciences Glutamate receptor Sensory Systems Ophthalmology medicine.anatomical_structure chemistry Biophysics sense organs Erg 030217 neurology & neurosurgery Photoreceptor Cells Vertebrate |
| Zdroj: | Vision Research. 180:80-86 |
| ISSN: | 0042-6989 |
| Popis: | The skate retina provides a native all-rod retina suited for investigating a single type of photoreceptor regarding its properties and signaling to second order cells. Using the aspartate-induced isolated A-wave of the skate eyecup electroretinogram (ERG), it has been shown that adaptation in rods remains Weber-Fechner-like over a 6-log unit increase in background light intensity. Zinc, which can block calcium channels, has been found in the rod synaptic terminal and the synaptic cleft. Histidine is a zinc chelator. Voltage signals from neurons post-synaptic to rods indicate that histidine increases the dark release of glutamate and increases the horizontal cell light response. In histidine, the A-wave response to various light intensities in the dark-adapted retina increased more than fifty percent, corresponding to the effect on horizontal cells. In the presence of background light, although histidine-treated rod light responses remained Weber-Fechner-like, their increment threshold was raised significantly. This indicates that endogenous zinc feedback serves to increase rod sensitivity in a light-adapted retina, despite a corresponding reduction of threshold sensitivity in the dark. We propose that the increase in A-wave amplitude is a result of the increased conductance at the synaptic terminal and that the A-wave can be used to monitor changes in rod transmitter release. Furthermore, endogenous zinc may also provide the benefit of reducing metabolic stress and the risk of glutamate toxicity in the dark. |
| Databáze: | OpenAIRE |
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