End-plate growth exceeds nerve terminal growth in juvenile mice

An electron microscopic investigation of neuromuscular synapses of the tensor fasciae latae muscle in juvenile mice was carried out to determine the relationship between the presynaptic (nerve terminal) and postsynaptic (end-plate plaque) elements during the major phase of postnatal growth. In the first month of life growth of the synapse was accompanied by a decrease in the size of pre- and postsynaptic elements in cross section. A decrease in the fraction of the width of end-plate plaque opposed by nerve terminal was also observed to age 2 months, and in older animal some end-plate plaques were completely unopposed by nerve terminal. This implies that end plates grow at a faster rate than nerve terminals and suggests that the availability of uninnervated, differentiated end plate permits or promotes nerve terminal growth.