Figure 6. The increase in [Ca²⁺]_i resulting from a single action potential is significantly higher than the increase due to either a sustained subthreshold depolarizing pulse or a tetanic synaptic train.

A, [Ca²⁺]_i increase evoked by a 500 ms subthreshold pulse and an AP. Ten trials were averaged. B, [Ca²⁺]_i increases generated by tetanic synaptic stimulation that did not evoke Ca²⁺ release and which was just subthreshold for generating an action potential. Ten trials were averaged. C, the AUC of the ΔF/F traces (as illustrated in A and B) were compared to the AUC in response to a single AP. The sample sizes are indicated in parentheses below each condition. The AUC of AP was significantly higher than both SSD and SY (*, one-way ANOVA, F= 166, P≤ 0.01, data taken from green ROI, opposite stimulating electrode). The AUC following SY was significantly greater than the AUC following SSD. D, the normalized AUC values of SSD were sorted and compared according to whether the cell was patched on the dendrite or on the soma. The values were not significantly different.