A, morphology of the simplified three-cylinder model neuron used in the study. B, voltage traces recorded at the midpoint of the oblique dendrite in response to a bAP at different A-conductance densities. C, [Ca2+]c traces in response to the bAPs shown in B. D, peak [Ca2+]c, in response to a bAP, plotted as a function of A-conductance density obtained from the experiments depicted in B–C. E, open probability of InsP3R (Po) plotted as a function of [Ca2+]c.