AMPA RECEPTOR-MEDIATED EPSCS IN RAT NEOCORTICAL LAYER II III INTERNEURONS HAVE RAPID KINETICS/

The properties of spontaneous and miniature (m) AMPA receptor-mediated excitatory postsynaptic currents (EPSCs) were studied in rat neocorti cal layer II/III fast spiking interneurons. Under optimal recording co nditions, averaged mEPSCs had a 10-90% rise time of about 0.3 ms. The decay of averaged mEPSCs was double exponential with time constants of about 1 and 4 ms. Kinetics were observed to slow as series resistance increased. The amplitudes of mEPSCs were much smaller at +50 mV than at -50 mV indicating that the currents were inwardly rectifying. These results suggest that synaptic AMPA receptors on neocortical inhibitor y interneurons have a deactivation time constant less than 1 ms which largely determines the decay of the synaptic currents. The receptors a ppear to lack GluR-2 subunits and may be Ca2+ permeable. (C) 1998 Else vier Science B.V.