Extraneuronal saxitoxin binding sites in rabbit myelinated nerve

Area of Science:

• Neuroscience
• Cell Biology

Background:

• Saxitoxin (STX) binds to voltage-gated sodium channels, primarily on nerve axons.
• Axonal injury triggers regeneration or degeneration, altering nerve structure and function.

Purpose of the Study:

• To investigate changes in STX binding in rabbit sciatic nerves during axonal regeneration and degeneration.
• To compare these changes with those observed in other mammalian species.

Main Methods:

• Measurement of 3H-labeled saxitoxin (STX) binding to rabbit sciatic nerves after crush injury and nerve section.
• Comparison with STX binding data from rat, guinea pig, and cat sciatic nerves.
• Assessment of STX binding after diphtheria toxin injection into rabbit nerves.

Main Results:

• Nerve crush in rabbits and rats increased STX binding, correlating with increased nodes of Ranvier.
• Nerve section in rats and guinea pigs led to a loss of STX binding, consistent with Wallerian degeneration.
• Rabbit nerves showed a maintained increase in STX binding after section, unlike other species.
• Diphtheria toxin abolished STX binding in cut rabbit nerves, suggesting non-neuronal binding sites.

Conclusions:

• Axonal regeneration increases STX binding in rabbits and rats, likely at nodes of Ranvier.
• Axonal degeneration in rats and guinea pigs eliminates STX binding.
• Rabbit nerves exhibit increased STX binding after section, attributed to proliferated Schwann cells.
• The nature and function of these Schwann cell binding sites in rabbits require further investigation.