TEMPORAL WHITE NOISE AND SAWTOOTH ELECTRORETINOGRAPHY AS A TOOL TO STUDY RETINAL GANGLION CELL ACTIVITY AFTER INTRAVITREAL TETRODOTOXIN INJECTION IN MICE

Aims: To examine the contribution of retinal ganglion cell (RGC) activity in ERG responses to sawtooth and temporal white noise stimuli (TWN) in mice. Tetrodotoxin (TTX) was injected to assess the contribution of RGC activity to the ERG.
Methods: ERG recordings to scotopic TWN and sawtooth stimuli were recorded in mice before and after intravitreal injections of 1 µL TTX at 6 mM (n = 5). Non-injected and PBS-injected eyes served as controls. Measurements were performed before injection, immediately after, and every 10 minutes up to 50 minutes post-injection. TWN stimuli contained all frequencies up to 20 Hz with equal amplitudes and random phases. Impulse response functions (IRF) were obtained by cross-correlation of the recorded signals with the stimulus. 4 Hz rapid-on-ramp-off (ON) and rapid-off-ramp-on (OFF) sawtooth stimuli were also presented. ON- and OFF-responses were added offline. Characteristic response components of the IRF and the sawtooth-responses were measured.
Results: TTX reduced the amplitude and increased the latency of the IRF’s initial positive (P1) and subsequent negative (N2) components. For sawtooth responses similar effects of TTX were observed in both ON- and OFF-responses, although the increase in response latency was less pronounced.
Conclusion: These findings support the notion of a substantial contribution of RGCs to ERG responses to TWN and sawtooth stimuli in mice. TWN and sawtooth stimuli can be a valuable tool to study RGC activity with the ERG.