Gap junctions in early amphibian embryos.

Cell pairs from late cleavage and early blastula Ambystoma mexicanum embryos were found to be electrotonically coupled. Thin-section electron microscopy revealed typical gap junctions between the cells. Freeze-fracture electron microscopy showed the gap junctions to be comprised of aggregations of 8.5-nm P-face particles and corresponding E-face pits. The conductance of the amphibian embryonic gap junction is known to be voltage-dependent, but no obvious gating structure was resolved by these morphological techniques.