Fig. 9. Quantitative analysis of dye coupling in CNCs. (A) Intracellular microelectrode impalement and iontophoretic injection of 6-carboxyfluorescein in a CNC explant culture plated on 15 µg/ml fibronectin. (B) Extensive dye spread can be seen in the same explant after 2 minutes of iontophoretic dye injection. The microelectrode was removed at this 2-minute timepoint. (C) More extensive dye spread can be seen in the same explant after an additional 2 minutes to allow for continued spread of the injected dye. (D). To assess the precise extent of dye spread from the impaled cell (0) to primary (1), secondary (2) and tertiary neighbors (3), the dark-field fluorescence image in C was merged with the cell outlines obtained by tracing the DIC image of the same area. Shown in red are cells in the secondary or tertiary cell layers that did not contain the injected dye. Scale bars: 100 µm.