Figure 6.

Ca²⁺-dependent intracellular acidification. A, Simultaneous monitoring of pH_i and E_gly with respect to 8 s of simple spiking (red) and complex spiking (black) in one cell. Arrowheads indicate glycine (2 mm) responses. The pH-sensitive dye SNARF-5F's signal is the average fluorescence intensity of a region of interest drawn inside the cell body. An intracellular acidification, manifested as a decrease in SNARF's signal, occurred during both simple spiking and complex spiking. The black bar above SNARF traces indicates the duration of 8 s depolarizing current injection. B, The intracellular acidification was also seen with Ca²⁺ spiking (in TTX) and inhibited by zero-Ca²⁺ (replaced with Co²⁺ or Mg²⁺) or 300 μm Cd²⁺. Bi–ii, Simultaneously recorded SNARF signal and E_gly from two cells. The 8 s depolarizing current injections evoking Ca²⁺ spikes or just depolarization after Ca²⁺ channel block are marked with thick bars above SNARF traces. The amount of injected current is shown beside each symbol along with the number of evoked Ca²⁺ spikes in parenthesis. An example of complete block (Bi) and incomplete block (Bii) of the depolarization-induced acidification by zero-Ca²⁺ is shown. Biii, Relation between the change in SNARF signal to the peak negative E_gly shift in control condition and the peak positive E_gly shift in Ca²⁺ block condition for eight cells. C, The changes in pH_i and [Ca²⁺]_i induced by 8 s complex spiking were detected by simultaneous two-photon imaging of SNARF-5F and Fluo-4 or Fura-2. Examples from two different cells are shown. The duration of 8 s depolarizing current injection evoking complex spikes is indicated by the shaded rectangle. The excitation wavelengths were 800 nm (Ci) and 780 nm (Cii).