Extracellular Calcium Levels Strongly Influence Neural Crest Cell Galvanotaxis

We have been studying the response of neural crest cells from 56-h-old quail embryos to small, imposed d.c. electrical fields. These cells exhibit directed translocation or galvanotaxis towards the negative pole of fields as low as 7 mV/mm. With an average cell length of 60 µm, these cells respond to fields as low as 0.4 mV along their length. A significant change in the average cosine of the cellular translocation distribution can be detected as early as 7 min after field application for all field strengths greater than 10 mV/mm. Extracellular Ca²⁺ is not required for the motility of these cells as long as extracellular Mg²⁺ is increased to 10 mM. However, the galvanotaxis response does appear to require Ca²⁺ influx since it is completely blocked by the addition of either 10 mM Mg²⁺ or 100 µM Gd³⁺. Moreover, the galvanotaxis response is partially reversed by the complete removal of extracellular Ca²⁺.