Regulation of cortical microcircuits by unitary GABA-mediated volume transmission

Excess neurotransmitter diffuses out of the synaptic cleft, where it can activate neurotransmitter receptors outside the postsynaptic density. However, neurotransmitter reuptake is thought to limit the significance of such extrasynaptic, or 'volume', transmission. Individual neurogliaform cells are now shown to release enough GABA for volume transmission within the axonal cloud; these cells do not require synapses to produce inhibitory responses in nearby neurons.