Figure 1.

Localized calcium transients occur in restricted regions of primary axons or their collateral branches. A, DIC image (top left) and fluorescence images of calcium activity (panels labeled F) in a cortical neuron in which calcium transients are localized to the primary axon (time point 9:45) or its collateral branch (time point 7:20). At 1:05, the neuron shows no calcium activity. Arrowheads (black and red) correspond to regions of localized calcium activity. Panels labeled F/F0 correspond to the same images shown above but show the fluorescence change from baseline. Pseudocolor calibration bars for images of raw fluorescence (F) and for fluorescence normalized to baseline (F/F0) are shown at right. The graph (bottom left) shows calcium activity measured in the primary axon (black), branch (red) and cell body (green) during the calcium transients shown in the fluorescence images (7:20, red arrow, 9:45, black arrow). B, DIC image (left) and fluorescence images of localized calcium activity indicated by black arrowheads in the primary axon of a cortical neuron (right panels). As shown in the graph of calcium activity (far right), localized calcium transients occurred only in the primary axon (black), making its average frequency of calcium transients much higher than that of the branch (red). One global calcium transient occurred near the beginning of the imaging session. Calibration bars as in A. C, Both the primary axon (black arrowheads) and branch (red arrowheads) show localized calcium transients but the branch has a higher frequency of calcium transients (graph, right). D, Distribution of total cortical neurons with different types of calcium activity. Pseudocolor scales are the same for all images of raw fluorescence and normalized fluorescence, respectively. Times are given in minutes and seconds. Scale bars, 10 μm.