Electroretinography.
Five ~6-mo-old male RanBP2+/+ and RanBP2+/− mice in 129ola background were kept in dim cyclic light (10 lux) for 2 wk before electroretinographic responses were recorded. The mice were anesthetized intraperitoneally with ketamine (80 mg/kg) and xylazine (4 mg/kg). Body temperature was maintained with a heating pad at 37.5 ± 1 °C throughout the recording. The pupils were fully dilated with 0.5% tropicamide and 2.5% phenylephrine HCl, and both eyes were recorded simultaneously. Corneal gold-wire loops were used as the active electrodes under 0.5% proparacaine hydrochloride topical anesthesia. Gold-wire electrodes placed on the sclera near the limbus served as reference electrodes. A ground wire was attached to the ear. Scotopic responses were recorded from threshold to 9 log units of intensity above threshold, amplified, and filtered (5,000 gain, 0.1–1,000 Hz). For photopic recordings background light at 34 cd/m2 was used to suppress rod function.