TITLE: SPARC - Acute surgery and experimentation of the gastrointestinal tract and vagus nerve 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 for acute surgery and electrophysiological experimentation on the anesthetized ferret, specifically for manipulating the vagus nerve and gastrointestinal tract nerve stimulation and myoelectric recording.</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 using isoflurane in a chamber, then move to a facemask (1 to 2%).
?. [Abdominal Surgery: Placement of electrodes and gastric tube/balloon]
Make an incision in the midline abdominal muscle to expose the organs.
?. [Abdominal Surgery: Placement of electrodes and gastric tube/balloon]
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/balloon]
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; in parallel with the gastric catheter is a 30 ml barostat balloon. 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/balloon]
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.
?. [Cuff Stim Trials]
Apply desired stimulation parameters (pulse width, current applitude, frequency) to abdominal vagus while recording. Record baseline data before and after trials and meaure impedances at the end.
?. [Abdominal Surgery: Placement of electrodes and gastric tube/balloon]
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
?. [Emetine Trial]
Record 20 min of baseline gastrointestinal myoelectric activity.
?. [Emetine Trial]
Use a syringe pump to infuse 5 mg/kg emetine into the stomach. Record for 1 hour.
?. Open abdomen and remove electrodes, balloon, and catheter.
?. Euthanize animal with intracardiac euthasol injection.
?. [Remove food]
Remove food from the home cage 3 h before anesthesia
?. [Remove food]
Measure body weight
?. [First incisions: Endotrachel tube and blood pressure catheter]
Make a ~3 cm incision on the medial surface of the right leg.
?. [First incisions: Endotrachel tube and blood pressure catheter]
Make a ~4cm incision in the ventral neck and dissection the trachea.
?. [Preparation: Before first incision]
Shave abdomen and ventral neck.
?. [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]
Monitor heart rate and body temperature throughout procedure and testing.
?. [First incisions: Endotrachel tube and blood pressure catheter]
Insert an endotracheal tube and coonect to pressure transducer to monitor respiration rate.
?. [First incisions: Endotrachel tube and blood pressure catheter]
Place blood pressure catheter in left femoral artery.
?. [Testing]
Following this initial setup various tests can be performed, including testing the effects of stomach distension, nerve electrical stimulation, and emetine infusion on gastrointestinal myoelectric responses. Emetine is a chemical emetic agent that produces retching and emesis when infused into the stomach and small intestine. Because emesis can produce strong abdominal contractions it is recommended that the abdominal incision is securely sutured.
?. [Abdominal Surgery: Placement of electrodes and gastric tube/balloon]
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.
?. [Abdominal Surgery: Placement of electrodes and gastric tube/balloon]
Test electrode impedances.
?. [Gastric distension trials]
Measure impedances of electrodes. Record 5 minutes baseline before and after each distension trial.
?. [Gastric distension trials]
Fill balloon using a syringe pump with 5 ml, 10 ml, or 20 ml saline. Infusion rate is 10ml/min. Saline is held in balloon for 5 minutes before deflation.