An electrical synapse connects the cytoplasm of two cells through intercellular channels called gap junctions. Small ions and selected small molecules can pass directly from one cell to the other.

Because electrical current can cross the junction without a released chemical messenger, the signaling path is short:

voltage change in cell A
        ↓
current through gap junction
        ↓
voltage change in cell B

Electrical synapses are fast

No vesicle release, extracellular transmitter diffusion or receptor-binding step is required before current enters the coupled cell. Electrical transmission can therefore have very little synaptic delay.

Coupling is often bidirectional

Many gap junctions permit current in either direction. If cell A becomes more positive than cell B, current can flow one way; if the voltage difference reverses, current can reverse.

Some electrical synapses are rectifying, meaning their molecular properties favor current more strongly in one direction than the other.

Electrical coupling can synchronize cells

If several neurons are connected electrically, a voltage change in one can influence its neighbors. This can help groups of cells change voltage together and synchronize rhythmic activity.

However, the voltage change transferred through the junction is generally a passive fraction of the source-cell change rather than a newly regenerated action potential at the junction itself.

Electrical and chemical communication use different architectures

Electrical synapses transmit current directly through intercellular channels. Chemical synapses instead use a released signaling molecule and receptors on the receiving cell. The direct electrical architecture favors speed and tight coupling, while chemical transmission permits a much wider range of receptor mechanisms and modulation.

The defining feature of an electrical synapse is therefore direct ionic current between cells through gap-junction channels.