Tracing axons of peripheral nerves in rats: a potential technique to study the equine recurrent laryngeal nerve.

The study investigated different methods of tracing axons in peripheral nerves, with the goal of applying the most effective method to study the equine recurrent laryngeal nerve, ultimately using a rat model for the initial comparisons.

Research Objective and Methodology

• The key aim of this study was to identify the most useful tracer for detailing the fascicular structures of the peripheral nerves.
• Three different groups of retrograde axonal tracers – fluorophores, horseradish peroxidase conjugated to subunit B of cholera toxin (CT-HRP), and adeno-associated virus (AAV) were evaluated in this study.
• The model used in this study were rat’s hindlimb nerves. This model was utilized to determine the tracer that would be most efficient in labeling axons within peripheral nerves.

Tracer Evaluation and Results

• The rat’s tibial and common peroneal nerves were injected with the various tracers.
• The sciatic nerve was then analyzed for evidence of labeled axons.
• The tracer that clearly provided outstanding results in this rat model was the CT-HRP.

Application to Equine Recurrent Laryngeal Nerve

• Following the successful identification of an effective tracer in the rat model, CT-HRP was then applied to the recurrent laryngeal nerve (RLN) of two horses.
• The objective was to identify the location and distribution pattern of the RLN axons within the pathway of the cervical vagus nerve trunk.
• Contrary to the results observed in the rat model, no labeling was observed in any of the two horses. This concluded that the CT-HRP tracer was inefficient in labeling the axons in the equine RLN.