Electrophysiology

Whole-cell electrophysiological recordings were performed on the stage of an Eclipse TE2000-S inverted microscope. Data were collected using with a Multiclamp 700B amplifier and Digidata 1440 data acquisition board (Molecular Devices) using pClamp 10 software. During experiments in which GABAergic and glutamatergic postsynaptic currents (PSCs) were studied, the intracellular pipette solution contained the following (in mM): 130 CsCl, 4 NaCl, 10 HEPES, 5 EGTA, and 0.5 CaCl₂. The pH was adjusted to 7.25 with NaOH. In all other experiments, the solution contained 130 CsMeSO₄ instead of CsCl.

Extracellular solution during whole-cell patch clamp recordings typically contained 138 mM NaCl, 4 mM KCl, 10 mM HEPES, 10 mM glucose, 2 mM CaCl₂, 1 mM MgCl₂, 1 μM NBQX, and 10 μM gabazine. During experiments in which GABAergic PSCs were recorded from neurons, 25 μM D-APV was used instead of 10 μM gabazine, and during experiments in which AMPAR PSCs were recorded, 25 μM D-APV was used instead of 1 μM NBQX. During experiments in which miniature postsynaptic currents (mPSCs) were recorded, 0.25 μM TTX was added. Antagonists were omitted in recordings from transfected N2a cells.

Whole-cell recording pipettes were pulled from borosilicate glass capillary tubes (World Precision Instruments) and had final open-tip resistances of 3–6 MΩ. Neurons were clamped at -70 mV unless otherwise stated. When drug delivery was performed, solutions were dispensed by a gravity-driven local perfusion system from a common tip with exchange time of ∼100 ms.