Transient and Sustained Ganglion Cell Light Responses Are Differentially Modulated by Intrinsically Produced Reactive Oxygen Species Acting upon Specific Voltage-Gated Na1 Channel Isoforms.

Increasing spike rates drive greater neuronal energy demand. In turn, mitochondrial ATP production leads to the generation of reactive oxygen species (ROS) that can modulate ion channel gating. Does ROS production autoregulate the excitability of a neuron? We investigated the links between retinal ganglion cell (RGC) excitability and spike activity-driven ROS production in male and female mice. Changes to the light-evoked and current-evoked spike patterns of functionally identified aRGC subtypes, along with their NaV channel-gating properties, were recorded during experimentally induced decreases and increases of intracellular ROS. During periods of highest spike rates (e.g., following light onset in ON sustained RGCs and light offset in OFF sustained RGCs), these aRGC subtypes responded to reductions of ROS (induced by catalase or glutathione monoethyl ester) with higher spike rates. Increases in ROS (induced by mercaptosuccinate, antimycin-A, or H2O2) lowered spike rates. In ON and OFF transient RGCs, there were no changes in spike rate during ROS decreases but increased ROS increased spiking. This suggests that endogenous ROS are intrinsic neuromodulators in RGCs having high metabolic demands but not in RGCs with lower energy needs. We identified ROS-induced shifts in the voltage- dependent gating of specific isoforms of NaV channels that account for the modulation of ON and OFF sustained RGC spike frequency by ROS-mediated feedback. ROS-induced changes to NaV channel gating, affecting activation and inactivation kinetics, are consistent with the differing spike pattern alterations observed in RGC subtypes. Cell-autonomous generation of ROS during spiking contributes to tuning the spike patterns of RGCs. [ABSTRACT FROM AUTHOR]