2.3. Electrophysiology recording
For an electrophysiological experiment, cultured neurons were put in the
upright microscope perfusion tank with extracellular bath solution (in
mM): 125 NaCl, 2 KCl, 3 CaCl2, 1 MgCl2,
10 HEPES, 30 Glucose, pH=7.3, 300 mOsm. Pipettes had a resistance of 2-7
MΩ when filled with internal solution (in mM): 135 potassium gluconate,
8 NaCl, 10 HEPES, 4 Mg-ATP, 0.4 Na-GTP, 0.6 MgCl2, 0.1
CaCl2, pH=7.25, 295 mOsm. After establishing whole-cell
configuration, cell capacitance and access resistance were routinely
compensated. All experiments were conducted in a whole-cell patch-clamp
configuration. For the recordings of action potentials, a switch to the
current clamp was performed. A current was injected to have membrane
potentials around -60 mV, then step currents from -40 pA to 50 pA were
injected to elicit action potentials by 10 sweeps. Pipettes were
prepared by a P-1000 micropipette puller (Sutter Instruments, Hofheim,
Germany). Recordings were performed using an EPC10 USB patch-clamp
amplifier (HEKA Elektronik, Lambrecht, Germany), data were digitized at
10 kHz.