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C.W. Hawryshyn, L. Anderson, T.J. Haimberger; Spectral Sensitivity of Cone Photoreceptors in Rainbow Trout, Oncorhynchus mykiss . Invest. Ophthalmol. Vis. Sci. 2006;47(13):3723.
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© ARVO (1962-2015); The Authors (2016-present)
To characterize the spectral sensitivity functions of cone photoreceptors in rainbow trout by recording membrane current responses to photostimulation (300–700 nm) using whole cell patch clamp electrophysiology. Such information can be compared with spectral sensitivity data previously obtained using ERG and MSP recording techniques. This study represents an initial step in our investigation of the retinal neural network mediating polarization sensitivity in rainbow trout.
Whole cell patch clamp recordings were used to measure photocurrent responses (pA) from individual cone photoreceptors in an isolated retina preparation from rainbow trout (O. mykiss). Photoresponse versus intensity curves were determined for individual cones across a range of test wavelengths in 10 nm increments. Normalized photoresponse (pA/pAmax) versus intensity (log photons•µm–2•s–1) curves were analyzed using a Naka–Rushton function. Threshold intensities required to produce a criterion response of 0.5 were used to generate spectral sensitivity functions. Spectral sensitivity functions for each of the four classes of cones were analyzed for fit against Govardovskii visual pigment templates to assess the chromophore ratio (A1:A2).
Results to date have generated four cone functions with the following mean max values: 565 nm (LWS cones, n=6), 516 nm (MWS cones, n=28), 429 nm (SWS cones, n=5) and 378 nm (UVS cones, n=2). Visual pigment template analysis indicates that the test fish used in this study have cone photoreceptors with predominantly A1 chromophore composition.
Whole cell patch clamp analysis of spectral sensitivity from individual cone photoreceptors reveals that the membrane current responses are well modeled through the use of the Naka–Rushton function and Govardovskii visual pigment templates. These results form the basis for further investigation of the processing of polarization sensitivity in the retina, in particular the role of interneuronal processing in the outer retina, by characterizing the current flow response of the input array.
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