Normative values for the mouse electroretinogram

Purpose The electroretinogram (ERG) is an appropriate method to evaluate th e retinal function in a variety of animal models. In this study we present suitable conditions of stimulation and recording in the dark-adapted mouse. Methods Mice (n = 15) were dark-adapted during 14 hours and anesthetized wi th a single intraperitoneal injection of xylazine/ketamine. Pupils were dil ated and a d.c.-silk-silver electrode or a AgCl-contact-lense electrode was placed on the cornea. The electroretinogram (ERG) was obtained by Ganzfeld stimulation over a range of 6 log units of intensity (8 x 10(-2) - 8 x 104 cd/m(2)). Intensity, duration and the intervall of the light stimuli were varied separately. Results Reproducible values of the intensity-response functions are obtaine d for the a-, b- and c-waves of the ERG under well controlled adaptation- a nd stimulus-conditions. C-wave amplitudes are best evaluated using d.c.-rec ording and a stimulus duration of 4 seconds. The position of the d.c.-silk- silver electrode on the cornea can affect the ERG-amplitudes. Using a conta ct-lense electrode, the recorded b-wave amplitudes are on average 20% below these recorded with a centrally positioned d.c.-silk-silver electrode. Sti mulus-intervalls of at least 60 seconds are recommended at high intensities . Conclusions An unequivocal assessment of retinal function requires reproduc ible ERG-values over a wide range of intensities. To obtain these, well con trolled and standardized experimental conditions are required.