Study of rod- and cone-driven oscillatory potentials in mice

PURPOSE. To characterize rod- and cone-driven oscillatory potentials (OPs) in mice. METHODS. Dark- and light-adapted electroretinograms (ERGS) were obtained in three mouse models: wild-type C57BL/6J mouse, cone photoreceptor function loss 1 (cpfl1) mouse, and rhodopsin knockout (rho(-/-)) mouse. A Butterworth filter was used to extract OPs from ERG signals. Latencies were calculated from the extracted OPs. Major frequency components were determined from OP power spectra computed using fast Fourier transform (FFT). The total power of the OP signal (an alternative measurement of amplitude) was calculated by numerically integrating the area enclosed by its frequency spectra, which is analogous to the total energy of mechanical vibration. RESULTS. In C57BL/6J mice, dark- and light-adapted ON had distinctly different peak frequencies (100 to 120 Hz and 70 to 85 Hz, respectively). In cpfl1 mice which possess pure rod ERGS, dark-adapted ON had a peak frequency similar to those of the wild-type mice, whereas light-adapted ERGS and OPs were not detectable. In rho(-/-) mice with pure cone functions, both dark-adapted and light-adapted OPs had peak frequencies of 70 to 90 Hz, which were similar to those obtained from light-adapted ON in wild-type mice. The total power of cone-driven OPs was less than 5% that of rod-driven OPs. In time-domain, cone-driven ON occurred approximately 13 ms after rod-driven OPs. CONCLUSIONS. Cone- and rod-driven OPs exhibit significantly different characteristics in peak frequency, latency, and total power. By using these characteristics, it is possible to differentiate cone- and rod-driven OPs in mouse models. Understanding these OP features is essential for analyzing OPs.