All (rod) amacrine cells form a network of electrically coupled Interneurons in the mammalian retina

All (rod) amacrine cells in the mammalian retina are reciprocally connected via gap junctions, but there is no physiological evidence that demonstrates a proposed function as electrical synapses. In whole-cell recordings from pairs of All amacrine cells in a slice preparation of the rat retina, bidirectional, nonrectifying electrical coupling was observed in all pairs with overlapping dendritic trees (average conductance similar to700 pS). Coupling displayed characteristics of a low-pass filter, with no evidence for amplification of spike-evoked electrical postsynaptic potentials by active conductances. Coincidence detection, as well as precise temporal synchronization of subthreshold membrane potential oscillations and TTX-sensitive spiking, was commonly observed. These results indicate a unique mode of operation and integrative capability of the network of All amacrine cells.