Basket-like interneurones in layer II of the entorhinal cortex exhibit a powerful NMDA-mediated synaptic excitation

Spiny stellate neurones of layer II of the entorhinal cortex (EC) provide the perforant path input to the dentate gyrus. Previous studies have shown that synaptic responses of these neurones are dominated by GABAergic inhibition. The present study describes intracellular recordings from 'fast-spiking' interneurones in layer II which may be the basis of the synaptic inhibition. Lucifer yellow fills of fast-spiking cells revealed neurones with a widespread axonal arborization forming basket-like complexes around unlabelled cells in layer II. Synaptic activation of the fast-spiking cells evoked long duration excitations which were mediated largely by NMDA receptors. A fast AMPA/kainate EPSP was also detectable. These neurones have morphological and physiological properties which make them well-suited to exert a widespread inhibitory control over the efferent output of layer II to the dentate gyrus.