Excitatory postsynaptic currents (EPSCs) were electrically evoked every 20 sec by 0.2 msec square-wave stimulation within the external capsule (EC) (Fig. 1A) using platinum/iridium concentric bipolar stimulating electrodes (FHC, Bowdoinham, ME) with an inner pole diameter of 25 μm and resistance of 8–12MΩ. Compound glutamatergic events were pharmacologically isolated using 10μM bicuculline to inhibit fast GABAergic transmission. In addition, kainate currents were isolated using 50μM DL-2-amino-5-phosphono-pentanoic acid (APV), a NMDA receptor antagonist, and 50 μM GYKI 53655 (1-(4-aminophenyl)-3-methylcarbamyl-4-methyl-3,4-dihydro-7,8-methylenedioxy-5H-2,3-benzodiazepine), an AMPA receptor-specific non-competitive antagonist. Recordings were acquired with an Axoclamp 2B amplifier (Axon Instruments, Foster City, CA) and digitized with a Digidata 1200B (Axon Instruments).
