PURPOSE Naturally-occurring Rpe65-mutant rd12 mouse was studied as models of human Leber congenital amaurosis (LCA). In its retinal morphologic examination, the cones were partly remained. But the light-adapted ERG from adult rd12 mouse showed abnormal wave with obviously delayed peak time compared with cone-response of age-matched C57BL/6J mice. In this study, we record and analyze white, red, green, blue flash ERG and white flicker ERG from rd12 mouse to explore the origin of the abnormal wave. The same responses of age-matched C57BL/6J mice are as control.
METHODS Adult rd12 and normal age-matched C57BL/6J mice were anesthetized with a solution of ketamine (15mg/g) and xylazine (5mg/g body weight). The pupils were dilated with a single drop of 1% atropine sulfate. A silver loop electrode was placed over the cornea to record the ERGs. Needle reference and groud electrodes were inserted into the cheek and tail, respectively. White, red, green and blue flashes were provided by a Gazfeld dome (Roland Q450, Germany). Light-adapted color flash ERGs and white flicker ERGs were recorded.
RESULTS In the retina of adult rd12 mouse, the cones were partly present. But the photopic-ERG elicited by white flash showed abnormal wave with obviously delayed peak time compared with normal cone-response. The response of red flash (with long wave-length) was existed and the amplitude of green flash (with middle wave-length) ERG was obviously smaller than that of blue (with short wave-length). The results were different from those of normal cone responses in C57BL/6J mice, but resemble to rod responses. Furthermore, high-frequency flicker ERGs can be used to distinguish rod system function from cone system function, because cones are capable to achieve higher Critical flicker frequency (CFF) than rods. In rd12 mouse, there was only low CFF left.
CONCLUSIONS The remaining cones of adult rd12 mice retina have no function. The abnormal light-adapted responses are due to the desensitized rod function.