Figure 3.

Dendritic specificity of Ca²⁺ signaling. A, Ca²⁺ transients are measured at different dendritic positions (from a to f) and are induced either by a 200 ms depolarization (dep) from -70 to 0 mV or by high-frequency mf stimulation (mf stim; 1 s at 100 Hz) while holding the cell at -70 mV in the absence of extracellular Mg²⁺. Note the decrease in ΔF/F₀ from the dendritic ending to the soma. Inset, Unprocessed fluorescence image revealing four dendrites in the focal plane, with indication of ROIs a-f used for ΔF/F₀ measurement. B, The histogram shows ΔF/F₀ at the end, amid, and at the origin of the dendrite during mf stimulation or membrane depolarization for seven recordings (including the one shown in A). Data are reported as mean ± SEM, and statistical difference from dendritic terminals is indicated: ^*p < 0.05; ^**p < 0.01; ^***p < 0.001. C, Pseudoratio images from the GrC in A showing ΔF/F₀ in control (left), in response to mf stimulation (middle), and in response to depolarization (right). Note the prominent ΔF/F₀ increases in dendrite 1 with mf stimulation and in both dendrites 1 and 2 during membrane depolarization (same cell as in A). The tracings below the images indicate ΔF/F₀ in the dendritic terminals 1 and 2 during mf stimulation and membrane depolarization. Error bars represent SEM.