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Henri Olavi Leinonen, Symantas Ragauskas, Heikki Tanila, Giedrius Kalesnykas; Simultaneous pattern ERG-VEP recording after optic nerve crush in albino rats. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5763.
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© ARVO (1962-2015); The Authors (2016-present)
The electroretinogram (ERG) and cortical visual evoked potentials (VEP) in rodents are powerful tools in ophthalmic drug research and beyond. While the flash stimulation evokes strong electrical currents to be recorded from cornea and skull surface, the response to pattern stimulation is smaller and more difficult to extract from the physiological noise especially in visually poor subjects. We tested if reliable pattern ERG and VEP responses can be recorded in albino Wistar rats in health and disease.
Nine male albino Wistar rats at the age of 12-14 weeks were used in this study. The left eye was subjected for 5 s lasting optic nerve crush (ONC) while the right eye was left intact (Co). The ERG was first recorded at 5 days post ONC. The eyes were one after the other stimulated by photopic flash and sinusoidal pattern stimuli. At 14 days post ONC, 4 screw electrodes were implanted in stereotaxical surgery bilaterally on the primary visual cortex and frontal cortex. After the surgery, ERG and VEP were simultaneously recorded with the same stimulation paradigm as before. All surgeries and recordings were performed under ketamine/medetomidine anesthesia.
Clear pattern ERG (PERG) response was recordable from all the rats from the both eyes at 5 days (PERG amplitude: Co=7.53±1.07µV vs. ONC=4.80±0.97µV, p=0.08) and 14 days post ONC (Co=5.65±0.76µV vs. ONC=2.47±0.32µV, p<0.05). The PERG response at 5 days vs. 14 days remained similar in the control eye (p=0.17) but decreased significantly in the ONC eye (p<0.01). The flash ERG (FERG) b-wave amplitude was similar in the control and ONC eye at 5 days post ONC (Co=239.7±19.5µV vs. ONC=208.1±27.29µV, p=0.36), but at 14 days post ONC the b-wave amplitude was decreased in the ONC eye compared to the control eye (Co=201.4±35.5µV vs. ONC=107.1±13.95µV, p=0.05). Pattern VEP (PVEP) or flash VEP (FVEP) responses could not be detected from the ONC eyes at 14 days post ONC. In the control eye VEP recording, there was a good correlation between PERG and PVEP amplitude (Spearman r=0.81, p<0.05) whereas correlation between FERG and FVEP amplitude was modest (r=0.23, p=0.55).
Although PERG responses after ONC injury in albino rats are very small they can be reproducibly recorded. We present a methodology to record stable pattern ERGs and VEPs simultaneously in rats that increases the diagnostic power compared to sole ERG recording.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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