It is now clear that electrical coupling via gap junctions is prevalent across the retina, expressed by each of the five main neuronal types. With the introduction of mutants in which selective gap junction
connexins are deleted, the mouse has recently become an important model for studying the function of coupling between retinal neurons. In this study we examined the tracer-coupling pattern of
ganglion cells by injecting them with the gap junction-permanent tracer
Neurobiotin to provide, for the first time, a comprehensive survey of
ganglion cell coupling in the wildtype mouse retina. Murine
ganglion cells were differentiated into 22 morphologically distinct subtypes based on
soma-dendritic parameters. Most (16/22)
ganglion cell subtypes were tracer-coupled to neighboring
ganglion and/or amacrine cells. The amacrine cells coupled to
ganglion cells displayed either polyaxonal or wide-field morphologies with extensive arbors. We found that different subtypes of
ganglion cells were never coupled to one another, indicating that they subserved independent electrical networks. Finally, we found that the tracer-coupling patterns of the 22
ganglion cell populations were largely stereotypic across the 71 retinas studied. Our results indicate that electrical coupling is extensive in the inner retina of the mouse, suggesting 0