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Norianne Theresa Ingram, Gordon Fain, Alapakkam P Sampath; Patch clamp recordings from mouse cone photoreceptores. Invest. Ophthalmol. Vis. Sci. 2017;58(8):1024. doi: https://doi.org/.
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The difficulty of making physiological and biochemical measurements from mouse cones has proved a substantial hurdle to understanding their function; as a result, much more is known about mammalian rods than cones. We are able to identify and patch-clamp single, unlabeled mouse cones even though cones represent only 3% of mouse photoreceptors. Voltage-clamp recording gives tight control over the electronics of the clamped cell and has not been used to study mouse cone phototransduction.
Mouse retinas were isolated under infrared illumination. Slices were cut to maintain vertical circuitry. Recordings were made from individual cone somas recorded in voltage-clamp or current-clamp in response to 405 nm light, which stimulates both spectral classes of cones equally.
We present the first voltage and current recordings from the same mouse cone. The maximum photocurrent averaged 24.5 ± 2.7 pA. (SEM, n =18) Wild-type (WT) cone flash and step responses show variable evidence of rod input, while Gnat1-/- cones do not show rod tails. We will also show flash and step responses of GCAP-/- and Rv-/- cones. A comparison of current and voltage responses in rods reveals significant temporal filtering: the photovoltage peaks before photocurrent and decays more rapidly. We do not see the same photovoltage speeding for mouse cones.
Individual mouse cones can be reliably located and patched in WT and other transgenic lines. Responses are 3-4 times larger than in previous studies using suction electrodes, yielding a greater signal-to-noise ratio. As the slice preparation maintains functional circuitry, our method can also be used to investigate the electrical properties of cones on a network level in addition to single-cell analyses. We propose this method as a powerful technique for probing cone physiology.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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