gms | German Medical Science

Objective: To evaluate threshold differences between different types of alpha retinal ganglion cells (α RGCs) based on differential axon initial segment (AIS) anatomy.

Materials and methods: Two different methods were used to recover AIS anatomy in α RGCs:

1.

Retinal whole-mounts from Thy-1 GFP mice were stained for AnkyrinG and ChAT.

2.

RGCs were filled in wild-type (C57BL/6J) mouse retinas and stained for streptavidin, AnkyrinG and ChAT. Multi-compartment models based on traced RGC anatomies were generated. AIS properties were varied according to anatomical measurements and activation thresholds in response to electric stimulation were computed.

Results: AIS length and distance from the soma varied depending on retinal location and cell type. Whereas AISs in ON- and OFF-α sustained RGCs displayed a size gradient along the nasal-temporal axis AISs in OFF-α transient RGCs tended to be longer in the dorsal vs. the ventral retina. For a given location, AISs were longer in ON- vs. OFF-α sustained RGCs. Computed activation thresholds were lowest when the AIS and the stimulating electrode were located close to each other. Longest AISs resulted in lowest activation thresholds allowing selective stimulation over cells with shorter AISs.

Discussion: Our results indicate that cell type selective activation of certain α RGC classes may be possible due to differences in AIS anatomy.

Acknowledgment: Research was supported by the VA (1I01RX001663), NINDS (U01-NS099700 & R01-NS110575) and FWF (J3947).