Extracellular Electrical Currents in the Chick Blastoderm.

Extracellular electrical currents were recorded using a computer-controlled scanning vibrating electrode from gastrulating chick blastoderms cultured in vitro. On the ventral surface, currents of 10-20 µA/cm diverged from the area opaca and turned around the margin of blastoderm across the vitelline membrane. Weaker currents (1-10 µA/cm) converged to the anterolateral area pellucida and penetrated it in the ventrodorsal direction. On the dorsal surface, currents returned to the area opaca from the margin and from the center of area pellucida. During development, the pattern of currents remained similar on the dorsal surface while the leaky area on the ventral surface progressively extended to all the periphery of area pellucida. The intensity of currents in the blastoderm oscillated with a period of 5 to 6 min. This spatio-temporal organization of extracellular currents is compared to physiological activities of embryonic cells in different regions of the blastoderm.