Coupling of gap junctions by induction of impulse conductivity in cultured epithelium of newt embryo (Cynops orientalis).

Impulse generation and propagation was previously shown to occur in skin epithelium of newt (Cynops orientalis) embryos during certain stages of development and to be correlated with morphological changes of gap junctions. These properties are not detected in embryonic epithelia explanted and grown in culture. However, early explants when transplanted to a host embryo develop conductivity, and relatively large gap junctions with loose arrangement of connexons occur as soon as the host embryo reaches the stage when conductivity is at its maximum. In contrast, morphological and physiological characteristics of impulse propagation are lost when the transplanted epithelium is extirpated from the host embryo and returned to in-vitro conditions. Therefore, it appears that impulse propagation is dependent not solely on the differentiation of epithelial cells but upon signals from non-epithelial (possibly mesodermal) tissue as well.