Dendrodendritic gap junctions: a developmental approach.

Dendrodendritic gap junctions have been identified in the periaqueductal gray substance of adult rabbits and in the visual cortex of sheep fetuses. The introduction of Alcian blue as a marker substance facilitated the positive identification of gap junctions. Dendrodendritic contacts in the human fetal neocortex have been examined in freeze-cleaved specimens. The contacts are identified as gap junctions by their freeze-fracture appearance. Features of the developing dendrodendritic gap junctions are described. The possible significance of these contacts is discussed, and it is suggested that they provide electrotonic coupling of neurons belonging to the same columnar organization. In addition it is suggested that the dendrodendritic gap junctions of fetal neocortex participate in cell differentiation and morphogenesis of the cerebral wall.