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HM Mayser, DJ Salchow, E Zrenner, MW Seeliger; Comparison of Two Techniques and Determination of Parameters for Multifocal ERG Recording in Mice . Invest. Ophthalmol. Vis. Sci. 2002;43(13):1793.
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Purpose: To compare two fundus image-controlled techniques for multifocal electroretinography (mfERG) in mice and to determine parameter settings for rod- and cone-selective stimulation on the basis of rod and cone-specific knockout mice. Methods: mfERGs were recorded in C57BL/6 mice in comparison to rhodopsin knockouts (pure cone function) and CNG3 knockouts (pure rod function) to assure the origin of visual activity. Recordings were performed with a special stimulator in connection with a VERIS 4 system and a Roland Consult RetiScan system, each together with a HRA scanning-laser ophthalmoscope (SLO) for fundus visualization. The stimulus of 19 or 37 unscaled hexagons was generated by a miniature CRT (VERIS) or by the argon laser (RetiScan). Results: Both systems revealed a growth of rod responses by an increase in the inter-stimulus interval (ISI) up to approx. 250ms (as shown in the CNG3-/- mice), whereas there was no major influence on the size of the cone responses down to an ISI of about 100-150 ms (as shown in the Rho-/- mice). Furthermore, we recorded the amplitude-vs.-intensity relationship at a fixed ISI of 250ms. With the Veris system, at 4 cd/m2 almost exclusively rod-driven signals were found, whereas at 400 cd/m2, only cone-driven signals were observed. Highest rod-driven voltages of 7-10 nV/deg2 were obtained at around 40cd/m2. With the Roland system, the largest, slightly higher rod-driven signals (up to 12nV/deg2) were obtained with edge filters featuring an attenuation between 97,2% and 99,6%. Conclusion: The use of rod- and cone-specific knockout mice allowed to determine the origin of mfERG response components recorded at different ISI and intensity settings and with two fundus image-controlled mfERG systems. These findings may be used to set up specific test conditions for the evaluation of animal models of retinal diseases.
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