Figure 7. Ca²⁺ waves suppress the amplitude of subthreshold [Ca²⁺]_i increases.

A, 2 s subthreshold depolarizing pulses (–85 to –55 mV in voltage clamp mode) generated small, persistent [Ca²⁺]_i increases in the dendrites. Transient changes were detected on the top of the slow [Ca²⁺]_i increases but not in the trough. Following the second pulse a UV flash (grey circle) generated a Ca²⁺ wave in the dendrites (arrow). The wave strongly reduced the slow signal and the number of transient changes at that location (black ROI) for more than 10 s after the wave. Indicator, 50 μm OGB-1. The data (grey traces) were filtered with a 5-point smoothing function (black traces) and the amplitudes of the steps were plotted for control conditions and following the UV flash. B, summary data from 6 cells. The Ca²⁺ wave clearly suppressed the amplitude of the subthreshold response.