For recording membrane and evoked potentials neurons were cultured on coverslips. In the set-up, coverslips were continuously perfused with extracellular solution containing (in mM) NaCl 125; NaHCO3 25; NaH2PO4 1.25; KCl 3; CaCl2 2; MgCl2 1; glucose 25; pyruvic acid 3, pH 7.2–7.4. Extracellular solution was maintained at a temperature of approximately 35°C and bubbled with 95% O2, 5% CO2. Glass capillaries (Harvard Apparatus) were pulled with a Flaming/Brown micropipette puller (Sutter Instrument) (tip resistance 3–10 MΩ) and filled with intracellular solution containing (in mM) potassium gluconate 135; NaCl 7; HEPES 10; Na2ATP 2; Na2GTP 0.3; MgCl2 2, pH 7.2–7.4. The voltage clamp technique in whole cell configuration using an EPC10 patch clamp amplifier (HEKA) was performed on cells with documented images. After a cell was successfully patched the resting membrane potential was recorded in zero current clamp mode before starting the experiments. To record action potentials (in current clamp mode), cells were injected with current to maintain the cells at a holding potential of −65 mV. Steps of 50 pA were applied to evoke spiking within a range of
