Patterns of intracellular calcium fluctuation in precursor cells of the neocortical ventricular zone.

Changes in intracellular free calcium concentration ([Ca2+]i) are known to influence a variety of events in developing neurons. Although spontaneous changes of [Ca2+]i have been examined in immature cortical neurons, the calcium dynamics of cortical precursor cells have received less attention. Using an intact cortical mantle and confocal laser microscopy, we examined the spatiotemporal patterns of spontaneous [Ca2+]i fluctuations in neocortical ventricular zone (VZ) cells in situ. The majority of activity consisted of single cells that displayed independent [Ca2+]i fluctuations. These events occurred in cells throughout the depth of the VZ. Immunohistochemical staining confirmed that these events occurred primarily in precursor cells rather than in postmitotic neurons. When imaging near the ventricular surface, synchronous spontaneous [Ca2+]i increases were frequently observed in pairs of adjacent cells. Cellular morphology, time-lapse imaging, and nuclear staining demonstrated that this activity occurred in mitotically active cells. A third and infrequently encountered pattern of activity consisted of coordinated spontaneous increases in [Ca2+]i in groups of neighboring VZ cells. The morphological characteristics of these cells and immunohistochemical staining suggested that the coordinated events occurred in gap junction-coupled precursor cells. All three patterns of activity were dependent on the release of Ca2+ from intracellular stores. These results demonstrate distinct patterns of spontaneous [Ca2+]i change in cortical precursor cells and raise the possibility that these dynamics may contribute to the regulation of neurogenesis.