Methods for Visualization of Pig Vagus Nerve "Vagotopy" Using Ultrasound

Surgically Expose the Vagus Nerve

Place subject in dorsal recumbence position.

Expose the length of the cervical vagus nerve by creating an incision (15-20 cm long) approximately 3 cm lateral and parallel to midline starting at the level of the mandible.

Divide tissue using blunt dissection to expose the carotid sheath, identifying and removing connective tissue from the carotid artery, vagus nerve and jugular vein.

Particular attention should be paid to clearing the vagus nerve at the most cranial point of interest (superior cervical ganglion, nodose/inferior cervical ganglion) to the caudal region of interest.

Place wire under the vagus nerve every 2-3 cm, where histology samples will be taken.

Depending on the diameter and type of wire, artifact will be created in the ultrasound to allow for histological matching. (ex: Silver (Ag) 0.015'' bare wire)

Fill the surgical pocket with room temperature/heated 0.9% Sodium Chloride (saline).

Collect ultrasound in regions of interest, or along the length of the vagus nerve.

Pat the vagus nerve dry with surgical gauze, or cotton tipped swabs above each wire.

Place histology dye as desired to mark the location of each wire along the length of the vagus nerve.

Recommended Histology Dye: Bradley Products, Inc., Davidson Marking System, Bloomington, MN.

Once histology dye has been placed in the desired locations, remove the vagus nerve and place in 10% Neutral Buffered Formalin for histological processing.

For Gomori's trichrome staining, please see our previously published protocol: dx.doi.org/10.17504/protocols.io.9ieh4be