Discrimination between the different compartments in sciatic nerve by 2H double-quantum-filtered NMR

Area of Science:

• Neuroscience
• Biophysics
• Analytical Chemistry

Background:

• Water dynamics within nerve tissues are crucial for understanding nerve function and pathology.
• Previous NMR methods struggled to resolve distinct water populations in nerve compartments.
• The sciatic nerve's complex structure presents challenges for compartmentalized analysis.

Purpose of the Study:

• To apply 2H double-quantum-filtered (DQF) NMR spectroscopy to distinguish and characterize water signals in different compartments of the rat sciatic nerve.
• To assign specific quadrupolar-split water signals to the epineurium, endoneurium, and intra-axonal spaces.
• To demonstrate the capability of DQF-NMR to measure properties of these distinct water populations independently.

Main Methods:

• Isolated rat sciatic nerves were equilibrated with deuterated saline.
• 2H double-quantum-filtered (DQF) NMR spectroscopy was employed to analyze water signals.
• Cobalt complexes (Co-EDTA2- and CoCl2) were used as shift reagents to track signal changes over time.
• Analysis of signal shifts and quadrupolar splittings allowed for compartment assignment.

Main Results:

• Three distinct quadrupolar-split 2H NMR water signals were identified in the rat sciatic nerve.
• Signals with splittings of ~120 Hz, ~470 Hz, and ~9 Hz were assigned to epineurial, endoneurial, and intra-axonal water, respectively.
• The DQF pulse sequence effectively suppressed the bulk water signal, enabling resolution of compartmentalized water.

Conclusions:

• 2H DQF-NMR is a powerful technique for resolving and characterizing water in distinct nerve tissue compartments.
• This method allows for independent measurement of water properties (e.g., relaxation times) in the epineurium, endoneurium, and intra-axonal space.
• The findings provide a foundation for studying water dynamics in nerve physiology and disease using NMR.