title: Robust mouse pattern electroretinograms derived simultaneously from each eye using a common snout electrode.
abstract: OBJECTIVE
  We recorded pattern electroretinograms (PERGs) simultaneously from each eye in mice using binocular stimulation and a common noncorneal electrode.
  
  
  METHODS
  The PERG was derived simultaneously from each eye in 71 ketamine/xylazine anesthetized mice (C57BL/6J, 4 months old) from subcutaneous needles (active, snout; reference, back of the head; ground, root of the tail) in response to contrast-reversal of gratings (0.05 cycles/deg, >95% contrast) generated on two custom-made light-emitting diode (LED) tablets alternating at slight different frequencies (OD, 0.984 Hz; OS, 0.992 Hz). Independent PERG signals from each eye were retrieved using one channel continuous acquisition and phase-locking average (OD, 369 epochs of 492 ms; OS, 372 epochs of 496 ms). The PERG was the average of three consecutive repetitions.
  
  
  RESULTS
  Binocular snout PERGs had high amplitude (mean, 25.3 μV, SD 6.6) and no measurable interocular cross-talk. Responses were reliable (test-retest variability within-session, 14%, SD 7; between sessions, 25%, SD 9; interocular asymmetry within-session, 9%, SD 7; between sessions, 13%, SD 5). Retinal ganglion cells (RGCs) were the main source of the binocular snout PERG, as optic nerve crush in three mice abolished the signal.
  
  
  CONCLUSIONS
  The PERG, a sensitive measure of RGC function, is used increasingly in mouse models of glaucoma and optic nerve disease. Compared to current methods, the binocular snout PERG represents a substantial improvement in terms of simplicity and speed. It also overcomes limitations of corneal electrodes that interfere with invasive procedures of the eye and facilitates experiments based on comparison between the responses of the two eyes.
authors.affiliation: Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, Florida, United States.
authors.forename: Tsung-Han
authors.initials: TH
authors.lastname: Chou
authors.forename: Jorge
authors.initials: J
authors.lastname: Bohorquez
authors.forename: Jonathon
authors.initials: J
authors.lastname: Toft-Nielsen
authors.forename: Ozcan
authors.initials: O
authors.lastname: Ozdamar
authors.forename: Vittorio
authors.initials: V
authors.lastname: Porciatti
mesh_terms: D000818:Animals; D004195:Disease Models, Animal; D004566:Electrodes; D004596:Electroretinography / Q000295:instrumentation*; D005901:Glaucoma / Q000175:diagnosis / Q000503:physiopathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D009900:Optic Nerve / Q000503:physiopathology*; D009901:Optic Nerve Diseases / Q000175:diagnosis / Q000503:physiopathology*; D010775:Photic Stimulation; D012165:Retinal Ganglion Cells / Q000502:physiology*
keywords: bioelectric field; mouse; noncorneal electrode; pattern electroretinogram; retinal ganglion cell