Developmental morphometry and physiology of the rabbit vagus nerve

Area of Science:

• Neuroscience
• Developmental Biology
• Physiology

Background:

• The vagus nerve plays a crucial role in autonomic regulation, particularly cardiac function.
• Understanding the developmental trajectory of the vagus nerve is essential for comprehending its physiological roles from birth.

Purpose of the Study:

• To investigate the morphological and physiological maturation of the rabbit vagus nerve after birth.
• To characterize the changes in myelination, fibre size, and conduction velocity during postnatal development.
• To assess the functional implications for cardiac innervation at different developmental stages.

Main Methods:

• Morphometric analysis of vagus nerve cross-sectional area and fibre counts at various postnatal ages.
• Histological examination to assess myelination and endoneural collagen content.
• Electrophysiological recordings of compound action potentials to determine nerve fibre conduction velocities.

Main Results:

• Vagus nerve cross-sectional area increases fivefold postnatally, driven by collagen, fibre growth, and myelination.
• Myelination is rapid in the first two weeks, followed by predominant axonal growth.
• Conduction velocities of nerve fibres increase significantly, with new fibre populations emerging post-birth.

Conclusions:

• Vagus nerve development involves substantial morphological and physiological changes, with myelination and axonal growth occurring sequentially.
• The development of myelin sheaths appears independent of axonal size.
• Functional cardiac innervation via the cervical vagus nerve is likely established at birth.