Full-field electroretinogram (ERG) is a mass electrical response of the retina to a light stimulus. The ERG contains two components, reflecting the response of the photoreceptors (a-wave) and ON bipolar cells (b-wave; Kofujj et al., 2000 J Neurosci 20: 5733-5740, 2000)
- Minimum number of animals : 2M + 2F
- Age at test: Week 16
- Sex: We do not expect the results of this test to show sexual dimorphism
Eye Dome-Diagnosys LLC, ColorDome, Espion3 System
- Transfer mice from animal room to the testing room
- Mice are weighed, and 1 drop of 1% Atropine (alternatively: Cyclopentate Hydrochloride Sol 1%) is placed in both eyes to induce mydriasis.
Place mice in dark adaption chamber.
- All rod testing procedures are done under dim red light after 2 hour dark adaptation
- After ~2hrs - using red headlamp in darkened room- Ketamine/Xylazine /saline solution (0.1ml/20g body weight) is injected (i.p.) to induce anesthesia and 1 drop of Cyclomydril (ophthalmic solutions) are applied to induce mydriasis.
Once the pupils have dilated and anesthetic agents have taken affect, the mouse is placed on a heating pad (38°C) and the electrodes are attached
- Tail (ground)
- between the eyes (up the nose bridge), mouth, or left cheek (reference)
Cornea loops (recording)
- Use one drop of Goniosol to moisten corneas
- The rod test is performed with a dim white light with varying stimulation intensities.
- A steady light (intensity) is turned on to isolate cone responses in rod tested mouse.
- After 8-10 minutes of light adaptation, cone ERGs are obtained with brighter white flashes at varying stimulation intensities.
- Optionally, a flicker test (testing the on-off bipolar cells) follows while the mouse remains in the dome: ~50 white flash intensities).
- Carefully remove the recording electrodes and clean with 70% ethanol and glass bead sterilizer.
- Anaesthesia reversal is promoted with a subQ injection of (~0.5ml) sterile saline and mouse recovers on a heating pad until fully conscious.
- Open indexing program and index and save rods and cones tests and graph
Amplitude and timing measures of the ERG waveform are taken:
- The a-wave amplitude measured from the pre-stimulus baseline to the negative trough of the a-wave; the b-wave amplitude measured from the trough of the a-wave to the following peak of the b-wave
- The implicit time (t) from flash onset to the trough of the a-wave and the peak of the b-wave (rod on left, cone on right) (Fig. 1).