Rod pathways in the mammalian retina use connexin 36

Many neurons in the mammalian retina are coupled by means of gap junctions. Here, we show that, in rabbit retina, an antibody to connexin 36 heavily l abels processes of AII amacrine cells, a critical interneuron in the rod pa thway. Image analysis indicates that Cx36 is primarily located at dendritic crossings between overlapping AII amacrine cells. This finding suggests th at Cx36 participates in homotypic gap junctions between pahs of AII amacrin e cells. Cx36 was also found at AII/cone bipolar contacts, previously shown to be gap junction sites. This finding suggests that Cx36 participates at gap junctions that may be heterotypic. These results place an identified ne uronal connexin in the context of a well-defined retinal circuit. The absen ce of Cx36 in many other neurons known to be coupled suggests the presence of additional unidentified connexins in mammalian neurons. Conversely, Cx36 labeling in other regions of the retina is not associated with AII amacrin e cells, indicating some other cell types use Cx36. (C) 2001 Wiley-Liss, In c.