For electrophysiological recordings, slices were transferred to the recording chamber and perfused at 1.5 mL min −1 with ACSF in the presence of 100 μm picrotoxin unless stated otherwise, bubbled with 95% O2 and 5% CO2, at room temperature (RT; 20–23°C). Slices were visualized with an upright microscope equipped with a × 63, 0·9 NA water-immersion objective and differential interference contrast (DIC) optics (Scientifica, UK).
Patch pipettes were made from thick-walled borosilicate glass capillaries with filament (GB150F-8P, Science Product) by means of a Sutter P-1000 horizontal puller (Sutter Instruments, Novato, CA, USA). Recordings were obtained in patch-clamp cell-attached configuration using an Axoclamp 200B amplifier (Molecular Devices, Union City, CA, USA).
For cell-attached recordings (10–80MΩseal resistance), patch pipettes were filled with standard extracellular saline. Pipettes were held at 0 mV in the voltage-clamp mode. Consecutive 140 s. current traces were filtered at 2 kHz and acquired at 50 kHz sampling rate. In these conditions, recorded spikes appear as biphasic current deflections (6M, right inset). Recordings were judged to be stable when the shape and frequency of spikes was constant over time (6M). Stable recordings were routinely obtained for as long as 20–30min (6M).
Patch pipettes were made from thick-walled borosilicate glass capillaries with filament (GB150F-8P, Science Product) by means of a Sutter P-1000 horizontal puller (Sutter Instruments, Novato, CA, USA). Recordings were obtained in patch-clamp cell-attached configuration using an Axoclamp 200B amplifier (Molecular Devices, Union City, CA, USA).
For cell-attached recordings (10–80MΩseal resistance), patch pipettes were filled with standard extracellular saline. Pipettes were held at 0 mV in the voltage-clamp mode. Consecutive 140 s. current traces were filtered at 2 kHz and acquired at 50 kHz sampling rate. In these conditions, recorded spikes appear as biphasic current deflections (6M, right inset). Recordings were judged to be stable when the shape and frequency of spikes was constant over time (6M). Stable recordings were routinely obtained for as long as 20–30min (6M).