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Myelination of the human vagus nerve from 24 weeks postconceptional age to adolescence
Insights
The vagus nerve
Area of Science:
- Neonatal physiology
- Neuroscience
- Respiratory regulation
Background:
- Respiratory reflexes are crucial for infant survival and undergo significant changes during maturation.
- The vagus nerve serves as the primary pathway for vital respiratory reflexes, including the Hering-Breuer and irritant-receptor reflexes.
- Understanding vagal nerve development is key to comprehending respiratory control maturation in infants.
Purpose of the Study:
- To quantitatively assess the development of myelinated vagus nerve fibers in infants.
- To compare vagal nerve fiber development between preterm and term infants and adolescents.
- To investigate the relationship between postconceptional age (PCA) and vagal nerve fiber characteristics.
Main Methods:
- Quantitative analysis of vagus nerve myelinated fiber counts in 33 infants and 5 adolescents.
- Categorization of infants into preterm (less than 38 weeks PCA) and term (greater than 41 weeks PCA) groups.
- Statistical analysis to determine correlations between PCA and fiber counts/percentages.
Main Results:
- Total myelinated vagus fibers increased linearly with postconceptional age in infants.
- By 40 weeks postconceptional age, total vagus nerve fiber counts in infants were comparable to adolescents.
- Preterm infants had significantly fewer total myelinated vagus fibers than term infants or adolescents.
- Smaller-diameter myelinated fibers were dependent on PCA in preterm infants but not in term infants.
- Preterm infants showed a higher percentage of small-diameter to total myelinated vagus fibers.
Conclusions:
- Vagal nerve myelinated fiber development progresses significantly with postconceptional age in infants.
- Preterm infants exhibit delayed vagal nerve maturation compared to term infants, potentially impacting respiratory control.
- These findings highlight the importance of considering vagal nerve development in the context of respiratory regulation in neonates.
Abstract:
Significant changes in respiratory reflexes occur with maturation. The vagus nerve, the pathway for the Hering-Breuer and irritant-receptor reflexes, was studied quantitatively in 33 infants and 5 adolescents. In the infants, total myelinated vagus fibers increased linearly (r m0.682, p less than 0.001) with postconceptional age (PCA), and by 40 weeks after conception, total counts were comparable to those of adolescent group. Counts of total myelinated vagus fibers in 16 term infants (greater than 41 weeks PCA) were comparable to those in the adolescent group (p less than 0.40), whereas 17 preterm infants (less than 38 weeks PCA) showed significantly fewer total myelinated vagus fibers than term or adolescent groups (p less than 0.001). Smaller-diameter (less than 2 micrometer) myelinated vagus fibers depended upon PCA in the preterm group (p less than 0.005), but were independent of PCA in the term group (p less than 0.5). Preterm infants have a higher percentage of small to total myelinated vagus fibers than term infants (p less than 0.1).