Different transmitter transients underlie presynaptic cell type specificity of GABA A,slow and GABA A,fast
Tóm tắt
Phasic (synaptic) and tonic (extrasynaptic) inhibition represent the two most fundamental forms of GABA A receptor-mediated transmission. Inhibitory postsynaptic currents (IPSCs) generated by GABA A receptors are typically extremely rapid synaptic events that do not last beyond a few milliseconds. Although unusually slow GABA A IPSCs, lasting for tens of milliseconds, have been observed in recordings of spontaneous events, their origin and mechanisms are not known. We show that neocortical GABA A,slow IPSCs originate from a specialized interneuron called neurogliaform cells. Compared with classical GABA A,fast IPSCs evoked by basket cells, single spikes in neurogliaform cells evoke extraordinarily prolonged GABA A responses that display tight regulation by transporters, low peak GABA concentration, unusual benzodiazepine modulation, and spillover. These results reveal a form of GABA A receptor mediated communication by a dedicated cell type that produces slow ionotropic responses with properties intermediate between phasic and tonic inhibition.