Abstract
Purpose :
We seek to investigate a novel microcircuit structure which has been identified in the mouse retinal ganglion cells (RGCs). We measured contributions of inter-RGC-type gap junction currents to ON and OFF polarity responses in two types of RGCs: the F-miniON and F-miniOFF.
Methods :
Experiments were performed on wild-type whole-mount mouse retina. Mice of both sexes and age approx. p30 were used. Retinal ganglion cells (RGCs) were recorded cell attached or whole cell (current clamp) using glass microelectrodes, with visual stimuli projected on the back of the retina using a digital projector. Spiking and subthreshold responses were analysed to determine effects of stimulus parameters and drug applications. The drug meclofenamic acid (MFA) was used to block gap junctions, and somatic ablation was used to remove RGCs from the microcircuit.
Results :
We found that F-miniON and F-miniOFF RGCs were strongly electrically connected to neighboring RGCs of the other type, with coupling coefficients > 0.1. We found that F-miniON RGCs receive primarily ON direct excitatory input, with MFA and somatic ablation of connected F-miniOFF RGCs decreasing OFF responses significantly relative to ON responses. We found that F-miniOFF RGCs receive only OFF direct excitatory input, with MFA and somatic ablation of connected F-miniON RGCs decreasing ON responses significantly relative to OFF responses.
Conclusions :
We find that two RGC types use strong gap junctional connectivity to mix ON and OFF polarity input and generate mixed ON and OFF feature selectivity. This novel microcircuit offers a highly tractable system for the study of gap junctional signal transmission in the retina.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.