Limited intercellular spread of spontaneous Ca2+ signals via gap junctions between mouse chromaffin cells in situ.

Using a confocal laser-scanning microscope, we measured the changes in the cytosolic Ca(2+) concentration ([Ca]i) of chromaffin cells on adrenal slice preparations of mouse. The spontaneous fluctuations of [Ca]i were often observed in situ, as reported in isolated rat and bovine cells. Intriguingly, the spontaneous [Ca]i changes in one cell were often transmitted to one or two adjacent cells, and the synchronized [Ca]i changes were often observed in two adjacent cells, both of which failed to respond to ATP. The synchronized [Ca]i changes between two cells were much less frequently observed in rat than in mouse adrenals. The spontaneous [Ca]i changes were also synchronized between closely touching mouse chromaffin cells in culture. These results suggest that the spread of Ca(2+) signaling is mediated by low-conductance intercellular coupling.