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Neuron. 2005 Nov 23;48(4):555-62.

Encoding light intensity by the cone photoreceptor synapse.

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Department of Molecular and Cell Biology and the Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, California 94720, USA.

Erratum in

  • Neuron. 2005 Dec 22;48(6):1067. Borghuis, Bart [corrected to Borghuis, Bart G].


How cone synapses encode light intensity determines the precision of information transmission at the first synapse on the visual pathway. Although it is known that cone photoreceptors hyperpolarize to light over 4-5 log units of intensity, the relationship between light intensity and transmitter release at the cone synapse has not been determined. Here, we use two-photon microscopy to visualize release of the synaptic vesicle dye FM1-43 from cone terminals in the intact lizard retina, in response to different stimulus light intensities. We then employ electron microscopy to translate these measurements into vesicle release rates. We find that from darkness to bright light, release decreases from 49 to approximately 2 vesicles per 200 ms; therefore, cones compress their 10,000-fold operating range for phototransduction into a 25-fold range for synaptic vesicle release. Tonic release encodes ten distinguishable intensity levels, skewed to most finely represent bright light, assuming release obeys Poisson statistics.

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