Inhibition of bAP-induced Ca²⁺ transients by uncaging of RuBi-GABA at oblique dendrites.

<p><b>A</b>, Fluorescence image (Alexa-594) of a dendrite investigated in (B,C). The red circle in the branch (Br) 1 represents uncaging point. Line scanning was performed along the yellow line for Ca²⁺ measurements. <b>B</b>, Current trace of 1pIPSC evoked at −20 mV. Uncaging of RuBi-GABA was applied to the red circle in (A). The red vertical line represents the time of GABA uncaging (0.5 mW, 4 ms). <b>C</b>, Normalized changes (Δ<i>F</i>/<i>F</i>) in fluorescence of OGB-1 (0.1 mM) evoked by a single bAP. Inhibition of the Ca²⁺ transients occurred at branch 1, but not at branch 2. Uncaging was applied 10 ms after bAP. Blue and red vertical lines denote the times for bAP induction and GABA uncaging, respectively. We masked the traces during 473 nm laser irradiation for GABA uncaging. <b>D</b>, Inhibition of bAP-induced Ca²⁺ transients in the branches which were applied with GABA uncaging or not. The amplitudes of the Ca²⁺ transients with GABA uncaging were normalized by those without. Bars represent the mean ± SEM. The relative values are different from 1.0 with ** <i>P</i><0.01 (<i>t</i>-test, <i>n</i> = 8). <b>E</b>, Time dependence of Ca²⁺ inhibition by GABA uncaging. Uncaging was applied 0 ms, 10 ms, or 20 ms after bAP induction. Ca²⁺ imaging was performed at the site of uncaging. The relative values differ from 1.0 with ** <i>P</i><0.01 (<i>t</i>-test, <i>n</i> = 6–10). <b>F</b>, Example of the effect of GABA uncaging on spike after-depolarization. <b>G</b>, Laser-power dependence of the amplitudes of 1pIPSCs induced by GABA uncaging at the soma. The correlation is significant (<i>P</i><0.001). <b>H</b>, Laser-power dependence of inhibition of the Ca²⁺ transients by GABA uncaging at oblique dendrites. The correlation is significant (<i>P</i><0.001).