Ionochromic properties of long-wave-sensitive cones in the goldfish retina: an electrophysiological and microspectrophotometric study

Long-wave-sensitive (LWS) cone visual pigments are sensitive to the concent ration of chloride ions and show a spectral shift to shorter wavelengths wh en exposed to low chloride levels. We have used the aspartate-isolated mass receptor potential of the electroretinogram (ERG) to establish whether the : spectrally shifted cone pigment is functional. In the goldfish, Carassius quratus, the lambda (max) of the LWS porphyropsin is displaced from about 622 nm to around 606 nm when chloride is replaced by gluconate. The electri cal response of the LWS cones (but not MWS cones and rods) is selectively a nd reversibly abolished by the removal of chloride ions. The effect is conc entration dependent and a decrease to half the normal chloride ion concentr ation is sufficient to cause a decrease in the response. (C) 2001 Elsevier Science Ltd. All rights reserved.