Abstract
Purpose :
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.
Methods :
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.
Results :
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.
Conclusions :
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.