Electroretinography 2 JAX_ERG_002

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Purpose

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)

Experimental Design

 

Equipment

Eye Dome-Diagnosys LLC, ColorDome, Espion3 System

Procedure

Procedure

  1.  Transfer mice from animal room to the testing room
  2.  Mice are weighed, and 1 drop of 1% Atropine (alternatively: Cyclopentate Hydrochloride Sol 1%) is placed in both eyes to induce mydriasis.
  3.  Place mice in dark adaption chamber.
    1. All rod testing procedures are done under dim red light after 2 hour dark adaptation
  4.  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.
  5.  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
    1. Tail (ground)
    2. between the eyes (up the nose bridge), mouth, or left cheek (reference)
    3. Cornea loops (recording)
      1. Use one drop of Goniosol to moisten corneas
  6.  The rod test is performed with a dim white light with varying stimulation intensities.
  7.  A steady light (intensity) is turned on to isolate cone responses in rod tested mouse.
  8.  After 8-10 minutes of light adaptation, cone ERGs are obtained with brighter white flashes at varying stimulation intensities.
  9.  Optionally, a flicker test (testing the on-off bipolar cells) follows while the mouse remains in the dome: ~50 white flash intensities).
  10. Carefully remove the recording electrodes and clean with 70% ethanol and glass bead sterilizer.
  11. Anaesthesia reversal is promoted with a subQ injection of (~0.5ml) sterile saline and mouse recovers on a heating pad until fully conscious.
  12. Open indexing program and index and save rods and cones tests and graph

Notes

Amplitude and timing measures of the ERG waveform are taken:

  1. 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
  2. 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).

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