Rectangular arrays of particles on freeze-cleaved plasma membranes are not gap junctions

Freeze-cleave replicas of adult rat diaphragm have revealed the presence of numerous small rectangular arrays of 60 Å particles (respectively pits) on the fracture faces of the sarcolemmas of the myofibers. Since these fibers are separated by thick basal laminae and are not electrically coupled we conclude that the rectangular arrays are not morphological equivalents of gap junctions as suggested by Staehelin 14]. The term “type III gap junctions” for these arrays therefore should be discontinued.