Purchase this article with an account.
F. Naarendorp, T. M. Esdaille, C. W. Van Slyck; The Rod-Mediated Threshold Response of Gnat-2-/- Mice Measured on High Intensity Backgrounds. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3055.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To determine the increment sensitivity of Gnat-2-/- mice that lack functional cones. Wild type (WT) rodent rods adapt to unusually high light levels (Sokolov et al., Neuron, 2002). In mice, the spontaneously occurring Gnat-2 mutation leads to cone dysfunction while the rods are spared (Chang et al., IOVS, 2006). Here we study rod vision of Gnat-2-/- mice at high light levels.
Adult wheel-running mice were trained to associate the presentation of a light flash with the brief availability of water at a spout in their cage. The light flash stemming from an intensity-controlled LED and mounted above the wheel was randomly triggered as the mouse ran on the wheel. A mouse was deemed to have detected the flash if it immediately ceased running within one revolution after the flash. A brief, 5 deg. test flash ( = 500 nm or 365 nm) was delivered in darkness or in the presence of a white Ganzfeld background light to the ventral retina. ‘Frequency of seeing’ data were collected with the method of constant stimuli. (1 R*s-1 stands for 1 photoisomerization per rod per second).
(1) In both WT and Gnat-2-/- mice, the flash produced 5-20 photoisomerizations at absolute threshold. (2) On a background that produced about 0.008 R*s-1, the rod threshold was raised to twice the absolute threshold. (3) In WT mice, a 365 nm test flash presented on a moderate background [25 R*s-1] was mediated by cones containing UV-opsin; in Gnat-2-/- mice, the 365 nm flash was mediated by rods. (4) In WT mice, at higher background levels [300 - 400 R*s-1], the 500 nm test flash was mediated by cones that contain M-opsin; in Gnat-2-/- mice, the 500 nm flash was mediated by rods. On backgrounds that produce ~30,000 R* s-1, the rods of Gnat-2-/- mice did not yet show saturation.
Rod vision of Gnat-2-/- mice is very similar to that of WT mice in low and moderate adapting ranges. Under very bright light, the sensitivity of the rods in Gnat-2-/- mice may be regulated by a light-adaptive mechanism that involves the translocation of transducin, from the rod photoreceptor outer segment to the inner segment as described by Sokolov et al. (Neuron, 2002).
This PDF is available to Subscribers Only