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T. Kaur, S. Nawy; Analysis of the Time–Dependent Recovery of Retinal on Bipolar Cells From Light–Induced Desensitization . Invest. Ophthalmol. Vis. Sci. 2006;47(13):392.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous studies of the retinal ONbipolar cells indicate that these cells quickly lose their ability to generate synaptic currents upon exposure to light, due to the Ca2+–dependent desensitization to neurotransmitter withdrawal of the signal transduction pathway that involves the mGluR6 metabotropic receptor and an unidentified cation channel. In order to further characterize the functional properties of this desensitization, we investigated the time–dependence of their recovery from the desensitized state by analyzing post–synaptic currents from inner–retina ganglion cells in conditions that mimic the light–to–dark–to–light transition. This procedure allows us to monitor the downstream response of the desensitized bipolar cells without disturbing their intracellular calcium concentration.
Retinal slices from larval tiger salamander were bathed in an agonist of the mGluR6 receptor (L–AP4) to mimic darkness. 500–milisecond puffs of CPPG were applied to mimic light stimulations and thus activate the ON bipolar cells, following a two–pulse protocol with variable time intervals, ranging from 3 to 45 seconds. The corresponding post–synaptic currents were recorded in ganglion cells, voltage–clamped to –60 mV.
Our results show that ON bipolar cells recovery from desensitization could be fitted with a single exponent. Time constants fall into two groups, with an average Tau of 6.509 sem 0.383 s in one, and 12.084 sem 0.407 s in the other.
The presence of two recovery rates suggests that there might be two or more types of ON bipolar cells in salamander retina, as has been proposed for mouse, or that there may be more than one mechanism of recovery.
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