Why does GABA produce both a fast and a slow inhibition? · Grey Matter

GABA acts on two different receptors.

Why does GABA produce both a fast and a slow inhibition?

GABA acts on two different receptors. The GABA-A receptor is a chloride channel that opens within a millisecond, and its current decays over roughly 5 to 10 ms at fast synapses (longer at others). The GABA-B receptor is metabotropic: it acts through a G protein that opens GIRK potassium channels, so the inhibition peaks after about 50 to 250 ms and decays over 100 to 500 ms. GABA-B receptors sit mostly outside the synapse and need GABA to spill over, so they come into play when inhibitory cells fire strongly or together, adding a long tail of quiet after intense inhibition.