Identified Sources and Targets of Slow Inhibition in the Neocortex

Abstract

There are two types of inhibitory postsynaptic potentials in the cerebral cortex. Fast inhibition is mediated by ionotropic γ-aminobutyric acid type A (GABA A ) receptors, and slow inhibition is due to metabotropic GABA B receptors. Several neuron classes elicit inhibitory postsynaptic potentials through GABA A receptors, but possible distinct sources of slow inhibition remain unknown. We identified a class of GABAergic interneurons, the neurogliaform cells, that, in contrast to other GABA-releasing cells, elicited combined GABA A and GABA B receptor–mediated responses with single action potentials and that predominantly targeted the dendritic spines of pyramidal neurons. Slow inhibition evoked by a distinct interneuron in spatially restricted postsynaptic compartments could locally and selectively modulate cortical excitability.