TITLE: SPARC - Chronic implantation of gastrointestinal and vagus nerve electrodes in the ferret
AUTHORS: Charles C. Horn, Derek M. Miller, Stephanie Fulton, Bill J. Yates, Lee E. Fisher, Ameya C. Nanivadekar

[DESCRIPTION]
<div class = "text-blocks"><div class = "text-block">This protocol is used to surgically implant gastrointestinal planar electrodes and vagus nerve cuff electrodes for chronic electrophysiological recording and stimulaiton in the ferret. Electrode lead wiring is tunneled subcutaneously to a connector embedded in a headcap affixed to the cranium.</div><div class = "text-block">Funding: This protocol was developed with funding from the NIH Common Fund’s Stimulating Peripheral Activity to Relieve Conditions (SPARC) program (Award U18TR002205). To learn more about the SPARC program, visit https://sparc.science.</div></div>

[STEPS]
?. [Preparation: Before first incision]
Induce anesthesia with 20mg/kg ketamine (i.m.).
?. [First incisions and Tunneling]
Make incisions in skin on the abdomenal midline (~4 cm) and dorsal neck (~3 cm).
?. [First incisions and Tunneling]
Use a trocar to tunnel under skin from the dorsal neck, along the back, and to the left side to exit at the abdominal incision.
?. [First incisions and Tunneling]
Advance electrode leads and gastric catheter through tunnel with trocar and then remove trocar leaving the leads under the skin.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Place the animal on its back.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Open abdominal cavity using a 3-point retractor (Balfour pediatric retractor; George Tiemann), applied to the lateral edges of the abdominal incision and sternum. This retractor is elevated using a vertical post attached to a surgical board under the animal.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Make incision (~0.5 cm) on the left lateral edge of the gastric fundus and insert gastric catheter with the tip resting in the antrum. Place a purse-string suture around the incision and tied. And, additional knot is made around the catheter and the free ends of this knot and purse-string suture are tied together. Finally surgical glue (Vetbond) is applied to the incision area.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
In some experiments, a cuff electrode is placed on either the ventral or dorsal abdominal vagus nerve trunk. Suture a ground electrode lead to connective tissue on the greater curvature of the stomach.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Place planar electrodes on surface of stomach and duodenum using 8-0 silk suture.  Suture a ground electrode lead to connective tissue on the greater curvature of the stomach
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Administer abdominal lavage with antibiotic (cefalexin, 1% w/v) in saline (0.9%, 100 ml).
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Test electrode impedances.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Close abdomen using absorbable suture for muscle (silk, 2-0) and monofilament (3-0) for the skin.
?. [Head mount: Securing the electrode connector]
Turn the animal to dorsal side up.
?. [Head mount: Securing the electrode connector]
Fix the head in place using stereotaxic frame and earbars.
?. [Head mount: Securing the electrode connector]
Make dorsal midline incision on the head.
?. [Head mount: Securing the electrode connector]
Tunnel under the skin between head and neck incision. Pull electrode connectors through to the head.
?. [Head mount: Securing the electrode connector]
Suture gastric tube to neck and close neck incision.
?. [Head mount: Securing the electrode connector]
Clear muscle tissue from dorsal skull.
?. [Head mount: Securing the electrode connector]
Drill 4 to 8 holes in the skull and place bone screws. Leave enough space between head of screw and skull to provide grip for bone cement.
?. [Head mount: Securing the electrode connector]
Layer bone cement onto skull to form a base.
?. [Head mount: Securing the electrode connector]
Use bone cement to mount connectors. Surround connectors with cement.
?. [Recording]
Measure electrode impedances.
?. [Recovery]
Extubate. Remove from isoflurane exposure.
?. [Recovery]
Monitor animal for recovery from isoflurane.
?. [Recovery]
Administer 10 days of oral amoxicillin and 72 hours of buprenorphine (s.c.).
?. [Recovery]
Remove sutures 2 weeks after surgery.
?. [Remove food]
Remove food from the home cage 3 h before anesthesia
?. [Preparation: Before first incision]
Apply facemask to delivery inhalational isoflurane (1 to 2%).
?. [Remove food]
Measure body weight
?. [Preparation: Before first incision]
Shave abdomen and dorsal neck and head.
?. [Preparation: Before first incision]
Intubate using a 3.0 or 3.5 endotracheal tube.
?. [Preparation: Before first incision]
Place ferret supine on table. Connect EKG leads and place rectal probe for recording body temperature (keep at 36 to 40C).
?. [Preparation: Before first incision]
Administer analgesic: 0.05mg/kg buprenorphine (s.c.).
?. [First incisions and Tunneling]
Leave ~6 cm of the leads with head connector extended from the dorsal neck incision, wrapped in sterile gauze and taped to surrounding skin.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
Make an incision in the midline abdominal muscle to expose the organs.
?. [Recording]
Record 10 min of baseline gastrointestinal myoelectric responses.
?. [Preparation: Before first incision]
Sterilize skin for incision with chlorohexidine and 70% isopropyl alcohol.
?. [Preparation: Before first incision]
Monitor vitals with pulse oximeter, EKG, rectal temperature probe. Animal prepped following sterile procedure.
?. [Preparation: Before first incision]
Administer 20 ml of warm saline (s.c.) and repeat every two hours.
?. [Abdominal Surgery: Placement of electrodes and gastric tube]
This is accomplished by caudal retraction of the stomach and retraction of the liver to the right side of the animal using saline moistened gauze. In this position, the esophagus and vagi become accessible.