Decrease of gap junction number in the rat neural tube between ED 11 and ED 15

The apical regions of neuroepithelial cells of 11 and 15 day-old rat embryos were found to be interconnected near their luminal surface by extended junctional complexes, consisting of tight junctions and desmosome-like contacts. On the 11th and 12th embryonal day, small gap junction cell contacts occur in the juxtaluminal region of the neural tube. Besides these intercellular gap junctions, annulated gap junctions, located intracellularly, were also detected at this developmental stage. The latter type is thought to originate from intercellular gap junctions by an invagination process in the course of degradation of extended contacts which exist between neuroepithelial cells in earlier developmental phases. The decrease of gap junction number by the 14th and 15th embryonal day could be correlated with processes of cellular development and differentiation.