An electrical synapse is a mechanical and electrically conductive link between two abutting neurons that is formed at a narrow gap between the pre- and postsynaptic cells known as a gap junction. At gap junctions, cells approach within about 3.5 nm of each other (Kandel et al. 2000), a much shorter distance than the 20 to 40 nm distance that separates cells at chemical synapses (Hormuzdi et al. 2004).