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End-plate growth exceeds nerve terminal growth in juvenile mice
Insights
During postnatal growth, neuromuscular synapses in juvenile mice show that muscle end plates grow faster than nerve terminals. This suggests that available, uninnervated end plates encourage nerve terminal development.
Area of Science:
- Neuroscience
- Developmental Biology
- Muscle Physiology
Background:
- Neuromuscular synapses are critical for muscle function.
- Postnatal development involves complex structural changes at the synapse.
- Understanding synapse development aids in comprehending neuromuscular disorders.
Purpose of the Study:
- To investigate the structural relationship between presynaptic nerve terminals and postsynaptic end-plate plaques in the tensor fasciae latae muscle during postnatal growth in mice.
- To determine how synapse dimensions change relative to each other during early development.
Main Methods:
- Electron microscopy was used to examine neuromuscular synapses.
- Quantitative analysis of presynaptic and postsynaptic element sizes and their opposition was performed.
- Juvenile mice at different postnatal ages were studied.
Main Results:
- Synapse growth in the first postnatal month correlated with decreased cross-sectional size of both pre- and postsynaptic elements.
- The proportion of end-plate plaque width covered by nerve terminals decreased with age, up to 2 months.
- In older mice, some end-plate plaques were found to be completely uninnervated.
Conclusions:
- Postnatal muscle synapse development exhibits differential growth rates between nerve terminals and end-plate plaques.
- End-plate plaques appear to grow faster than the innervating nerve terminals.
- The availability of uninnervated, differentiated end-plate regions may facilitate or drive nerve terminal expansion.
Abstract:
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.