Abstract
Abstract: :
Purpose: Oscillatory potentials (OPs), the inner retina electroretinogram (ERG) components, are elicited with high intensity stimulation light which activates both rod and cone systems. Therefore, OPs contain signals generated from both rod– and cone–pathways. We test this hypothesis and characterize rod– and cone–driven oscillatory potentials (OPs) in mice. Methods: Wild–type C57BL/6 mice, cone photoreceptor function loss 1 (cpfl1) mice, and rhodopsin knockout (rho–/–) mice were used. Dark– and light–adapted ERGs were recorded and the OPs were extracted digitally with a Butterworth filter. After removing the low frequency contaminations, the frequency spectrum was studied with Fast Fourier Transform (FFT). Instead of using summed individual OP amplitude (ΣOPs, µV), we measured the band area beneath the frequency spectrum curve of OPs (analogous to energy of mechanical vibration, in µV2sec), which represents OPs more accurately. Results: In wild–type mice, OPs peak frequency was 100∼120 Hz for dark–adapted ERGs and 75∼85 Hz for light–adapted ERGs. In cpfl1 mice which have pure rod function, dark–adapted OPs frequency was 100∼115 Hz. In rho–/– mice which have pure cone function, dark–adapted and light–adapted OPs were 78∼90 Hz. The energy ratio of cone–driven/rod–driven OPs is 0.015∼0.044. In time domain analysis, cone–driven OPs are about 22 ms later than rod–driven OPs. Conclusions:Our results demonstrated that conventional OPs contain responses generated from both rod– and cone–pathways. Cone–driven OPs frequency is lower than rod–driven OPs. The latency of cone–driven OPs is later than rod–driven OPs. Therefore, in dark–adapted ERGs, OP1 and OP2 are purely rod–driven, while OP3, OP4 and OP5 contain inputs from both rod and cone pathways. In rod dominant mice, however, the energy of cone–driven OPs is minimal.
Keywords: electroretinography: non–clinical • retina: proximal (bipolar, amacrine, and ganglion cells) • retinal connections, networks, circuitry