Abstract
Purpose::
To characterize the local retinal circuits of the intrinsically photosensitive retinal ganglion cells (ipRGCs) using transsynaptic viral tracing, electrophysiology and immunohistochemistry.
Methods::
PRV152, a GFP-expressing retrograde transsynaptic viral tracer, was injected into the anterior chamber of the mouse eye to label cells in the contralateral retina via the pupillary reflex pathway. Infected retinas were isolated, superfused and GFP-positive ganglion cells were detected with two-photon laser imaging. Light-evoked inhibitory currents were measured from the labeled ganglion cells using electrophysiological techniques. Retinas were fixed and immunohistochemistry was used to identify cell types.
Results::
After four days incubation, PRV152 labeled three distinct morphological subtypes of melanopsin-positive ipRGC that showed differences in stratification in the inner plexiform layer. Longer incubation times resulted in amacrine cell labeling. Müller cells were labeled only from ipRGCs and not from ganglion cell types that project to the lateral geniculate nucleus. Electrophysiological recordings from GFP-positive ipRGCs were consistent with the anatomy of the labeled circuits. Immunohistochemistry revealed that GFP-labeled amacrine cells were positive for tyrosine hydroxylase, indicating that dopaminergic interplexiform amacrine cells are synaptically connected to ipRGCs.
Conclusions::
We revealed that dopaminergic amacrine cells are presynaptic to at least one ipRGC subtype in the mouse retina.
Keywords: retina: proximal (bipolar, amacrine, and ganglion cells) • ganglion cells • amacrine cells