Impact of MB-001 and fenretinide treatment on ground squirrel ERG responses to a range of flash intensities. (A) Ground squirrel ERG responses to a flash series were measured on day 1 before any drug or vehicle treatment both before and after a 10-min photobleach. (B–E) The responses were measured again in the same fashion 3 d later after daily administration of vehicle, MB-001 at 8 mg/kg/day, MB-001 at 80 mg/kg/day, and fenretinide at 166 mg/kg/day. The final dose of drug was administered ∼2 h before the ERG recordings. The left graphs show ERG traces for each type of treatment. The arrows indicate the time of flash onset. The middle panels show a-wave responses to each flash, and the right panels show the corresponding graphs for b-wave responses. The luminance-response plots of A show averaged data for all animals studied (n = 10). The luminance-response plots for B–E show the posttreatment responses for the individual animals studied (red and orange circles for pre- and posttreatment responses, respectively) along with the averaged day 1 responses (mean shown as a dashed line with the SDs shown as shaded error bars). Vehicle-treated group, n = 3; 8 mg/kg MB-001–treated group, n = 2; 80 mg/kg MB-001–treated group, n = 2; fenretinide-treated group, n = 3. Apart from a single animal in the high-dose MB-001 group (D), the pre- and postbleach responses in drug- and vehicle-treated animals were highly similar to the day 1 pretreatment responses. The greater responses in the single animal may have been caused by off-target drug toxicity.