Figure 5. Whole-cell axonal Ba²⁺ currents are not modulated by the application of 5-HT.

A, an axon was voltage clamped at -70 mV and 10 mV increments of test potential were applied from -70 to +40 mV to evoke a Ca²⁺ conductance carried by Ba²⁺. The peak current was measured at each test potential to generate this current-voltage plot (•). ○, peak amplitude after application of 5-HT (30 μm) to the superfusate, for 3 data points. B, raw data traces of Ba²⁺ current in control conditions and in the presence of 5-HT (30 μm) when the holding potential was ‘jumped’ from -70 to 0 mV. The patch solution contained Cs⁺ as the primary charge carrier and the external solution contained Ba²⁺ (2.6 mm), TTX (1 μm) and 4-AP (1 mm). C, same traces as in B but on an expanded time base.