Abstract
We measured fraction of open channels in gap junctions of retinal horizontal, amacrine (J Intgra Neurosci, 2005) and ganglion cells (J Neurosci, 2004). The open fraction in retinal neurons expressing connexins was on the order of 0.1 to 1. The open fraction is small, when we consider whether electrotonic transmission acts to synchronize action potentials and extends the size of receptive fields beyond the diameter of dendritic fields (space length constant λ > 1.9 mm). Although our study showed that similar properties of electrical synapses are present in amacrine cells expressing the specific connexin, it is very likely that different types of amacrine cells make differential inhibitory synapses. Electrical current spread through connections of specific amacrine cell types is expected to synapse certain inhibitions. Here I investigated cellular components in several amacrine cells performing lateral electrical interactions in the inner plexiform layer. I measured cells' receptive fields by microelectrode technique and gap junction conductance between these cells by dual patch-clamp methods. In high-voltage electron microscopy (Hitachi H-1250M, NIPS, 2007HVEM-13) and freeze-fracturing, dendritic location, size and packing density of gap junction connexons were measured. This study shows that current decay through electrical synapses of amacrine cells was correlated with a total number of gap junction connexin channels localized on their dendritic tips. [J Physiol Sci. 2008;58 Suppl:S174]
