Measurement of Electroretinograms and Visually Evoked Potentials in Awake Moving Mice

Abstract

The development of new treatments for intractable retinal diseases requires reliable functional assessment tools for animal models. In vivo measurements of neural activity within visual pathways, including electroretinogram (ERG) and visually evoked potential (VEP) recordings, are commonly used for such purposes. In mice, the ERG and VEPs are usually recorded under general anesthesia, a state that may alter sensory transduction and neurotransmission, but seldom in awake freely moving mice. Therefore, it remains unknown whether the electrophysiological assessment of anesthetized mice accurately reflects the physiological function of the visual pathway. Herein, we describe a novel method to record the ERG and VEPs simultaneously in freely moving mice by immobilizing the head using a custom-built restraining device and placing a rotatable cylinder underneath to allow free running or walking during recording. Injection of the commonly used anesthetic mixture xylazine plus ketamine increased and delayed ERG oscillatory potentials by an average of 67.5% and 36.3%, respectively, compared to unanesthetized mice, while having minimal effects on the a-wave and b-wave. Similarly, components of the VEP were enhanced and delayed by up to 300.2% and 39.3%, respectively, in anesthetized mice. Our method for electrophysiological recording in conscious mice is a sensitive and robust means to assess visual function. It uses a conventional electrophysiological recording system and a simple platform that can be built in any laboratory at low cost. Measurements using this method provide objective indices of mouse visual function with high precision and stability, unaffected by anesthetics.

Single AAV-mediated scarless genome editing in dysfunctional retinal neurons mediates robust visual restoration in mice

“…Basic equipment and techniques for ERG and fVEP recordings were carried out as previously described. 30 Scotopic 6-Hz flicker ERGs were recorded following a previously published protocol 31 with modifications. We used flash intensities at 7 steps, ranging from −6.0 to 0 log.cd.s m −2 , separated by 1.0 log units.…”

“…Surgical implantation of the VEP electrodes was carried out as previously described 30, 32 5 weeks post-injection, and recording was performed a week later. For recording fVEPs, we used flash intensities at 9 steps, ranging from −7.0 to 1.0 log.cd.s m −2 , separated by 1.0 log units.…”

Improved daylight vision following AAV-mediated expression ofR9APin murine rod photoreceptors

“…Before recording VEPs from the visual cortex, electrodes were surgically placed according to the following procedures 36 . Mice were anesthetized by a single intraperitoneal injection of medetomidine hydrochloride (0.6 mg/kg, Meiji Co. Ltd., Tokyo, Japan) and ketamine (36mg/kg, Daiichi-Sankyo, Tokyo, Japan).…”

Vision in laboratory rodents—Tools to measure it and implications for behavioral research

“…The ERG is recorded from the corneal surface, with electrodes placed either on the bulbar conjunctiva or the lower eyelids in humans [100]. In laboratory animals, the recording is generally performed in anesthetized animals, although a non-anesthetized procedure has also been published [101]. The conventional ERG response is based on changes in ion currents within the retina upon a flash of light.…”