Skeletal muscle fibers of newborn rats are coupled by gap junctions

In the soleus muscle and in the short muscles of the hindfoot of the newborn rat many muscle fibers are arranged in clusters comprising two to four fibers enclosed by a common basal lamina. The fibers of a cluster are connected by gap junctions which were seen in thin sections and in freeze-fractures. One week after birth, almost all fibers have detached; no gap junctions were found.