= Electrical synapse
{wiki}
An <electrical synapse> passes ionic <electric current> directly between <neurons> through <gap junctions>, whose paired channels connect the two <cytoplasms>. It does not require <synaptic vesicle> release and postsynaptic <neurotransmitter> binding. Transmission across the junction is very fast; the receiving <cell membrane>'s <capacitance> and other conductances still determine its voltage response. Electrical coupling can coordinate the timing of activity across <neurons>. See https://www.ncbi.nlm.nih.gov/books/NBK11164/[Purves and colleagues: electrical synapses and gap junctions].
For a passive junction with constant conductance $g_j$, the inward <electric current> into cell 2 is
$$
I_{2\leftarrow1}=g_j(V_1-V_2),\qquad I_{1\leftarrow2}=-I_{2\leftarrow1},
$$
where each $V_k$ is the cell's <membrane potential>, measured against a common extracellular reference. Taking $g_j=2\,\mathrm{nS}$, $V_1=-55\,\mathrm{mV}$ and $V_2=-65\,\mathrm{mV}$ gives $20\,\mathrm{pA}$ into cell 2 and the equal opposite <electric current> into cell 1. Exchanging the voltages reverses the <electric current>. Both <depolarization> and <hyperpolarization> can therefore be transmitted; an <electrical synapse> is not inherently an excitatory connection.
Many <electrical synapses> conduct in both directions, but this does not guarantee equal voltage responses: the cells can have different effective <electrical resistance> and <capacitance>. Some junctions rectify, meaning they conduct preferentially in one direction, so the constant-$g_j$ formula is insufficient. A concrete molecular example is the original study https://pmc.ncbi.nlm.nih.gov/articles/PMC7455501/[Shui and colleagues, 2020: Molecular basis of junctional current rectification at an electrical synapse]{ref}. Bidirectionality is thus a common property with important qualifications, rather than part of the definition.
Back to article page
