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Josue Franco, Andre Herrera, Shannon Saszik; Optic nerve crush alters the light adapted ERG of adult zebrafish. Invest. Ophthalmol. Vis. Sci. 2018;59(9):5519.
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© ARVO (1962-2015); The Authors (2016-present)
While zebrafish (Danio rerio) are considered to be an excellent model for visual neuroscience little has been done to understand the cellular contributions to the electroretinogram (ERG). The purpose of the current study is to examine inner retinal contributions to the light adapted ERG of adult zebrafish after optic nerve crush and injection of pharmacological agents that block responses of amacrine and ganglion cells.
Light adapted ERGs were recorded in adult zebrafish (N=27) using standard procedures (CON), post optic nerve crush (ONC), and post intravitreal injection of 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) (1-2 μL at 100 μMolar). For ONC, zebrafish were anesthetized and the eye was rolled slightly to expose the optic nerve. The nerve was crushed with forceps for 3 seconds. The fish were placed in a 2.5-gallon tank for recovery. Three to five days after ONC, fish were anesthetized and ERGs were recorded. In both CON and ONC injection was done with a glass pipette attached to a hamilton microsyringe. ERG responses were recorded to 50 ms and 1000 ms flashes of light of varying intensities. The time to peak (TTP) and peak amplitude of each ERG response was measured. Intensity response functions were plotted in order to examine group differences of both TTP and peak amplitude.
For all groups there was a decrease in the TTP as the flash intensity increases. However, there was an overall increase in the TTP after ONC and CNQX (CON M=222.7, SEM=1.7 ms, ONC M=269.6, SEM=13.9 ms, CNQX M=384.1, SEM=12.4 ms). The peak amplitude of the ERG increased as the flash intensity increased, however the initial rise of the intensity response function was nonlinear in CON. After ONC there is a 10% reduction in the peak amplitude at the weakest flash intensities, reducing the amount of nonlinearity present in the intensity response function. In both CON and ONC, CNQX reduced the peak amplitude for the b-wave for flash intensities with the percentage reduction being greater after ONC.
The increase in the TTP after both ONC and CNQX suggest an inner retinal contribution to early times in the light adapted ERG. The reduction in the b-wave peak amplitude at the weak flash intensities suggest that inner retinal neurons contribute to the light adapted ERG, similar to previous research in other species. Together, these findings support the use of the zebrafish as model system to understand inner retinal circuitry.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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