Increasing internodal distance in myelinated nerves accelerates nerve conduction to a flat maximum

Area of Science:

• Neuroscience
• Cell Biology

Background:

• Myelinated axons have nodes of Ranvier, and internodal length is crucial for nerve function.
• Schwann cells form myelin, and their elongation determines internodal length.
• Previous studies suggest internodal length affects conduction velocity, but experimental evidence is limited.

Purpose of the Study:

• To investigate the functional relationship between internodal length and nerve conduction velocity.
• To examine the role of periaxin in Schwann cell elongation and its impact on myelination and conduction speed.

Main Methods:

• Utilized mice expressing a mutant periaxin to alter Schwann cell elongation and internodal length.
• Assessed nerve conduction velocity and motor/sensory behavior in young and developing mice.
• Examined myelination and axon caliber in mutant mice.

Main Results:

• Mutant mice with short internodes exhibited reduced nerve conduction velocity and impaired motor function.
• Internodal lengthening during postnatal growth led to recovery of conduction velocities to normal levels.
• Mutant mice showed normal motor and sensory behavior as internodes lengthened.

Conclusions:

• Demonstrates a direct functional link between internodal distance and nerve conduction speed.
• Supports predictions that conduction velocity increases with internodal length up to a 'flat maximum'.