Recordings of spontaneous synaptic currents (sPSCs) were made at room temperature using the voltage clamp technique in whole cell configuration using an EPC10 patch clamp amplifier (HEKA). Synaptic activity was sampled at 20 kHz and stored on a PC and subsequently filtered at 1 kHz with a Bessel filter using Patchmaster software (HEKA), running on a PC. Coverslips were placed into petri dishes and fixed on the stage of a Patch Clamp Tower (Luigs and Neumann). An inverted microscope (Olympus IX-50; Luigs and Neumann) was used to observe the cells. Patch pipettes were pulled from borosilicate glass capillaries (outside diameter 1.5 mm, inside diameter 0.87 mm; Hilgenberg) using a horizontal Flaming/Brown micropipette puller (Sutter P-97; Science Products). The pipettes were filled with (in mM) NaCl 10; KCl 120; MgATP 2; HEPES 10; D-glucose 25; GTP 0.1; pH 7.2 with KOH. Spontaneous synaptic activity was recorded in cells maintained in culture for 5 weeks at a holding potential of −80 mV in the presence of extracellular solution containing (in mM) NaCl 141.5; KCl 3; CaCl2 2; HEPES 10; D-glucose 25; pH 7.4 with NaOH.
