Measuring the Visceromotor Response in Rodents

Prepare surgical area in accordance with institutional requirements.

• Clean and sterilize instruments

• Warm heating pad

• Check all equipment prior to starting

Prepare the mouse

• Anesthetize with 1.5% inhaled Isoflurane

• Shave neck and right abdomen

• Clean exposed skin with Betadine

Surgical incisions

• Make a small (< 1 cm) skin incision in right lower abdomen above the inguinal region to expose the abdominal muscle

• Turn over mouse and make small incision on nape of neck

Wire Placement

• Tunnel sterile cannula subcutaneously from neck incision along the side of the mouse and out the abdominal incision taking care to not injure/enter the abdominal compartment

• Thread two sterilized EMG wires (~20cm length) through cannula. Holding the wires from the abdominal side, withdraw the cannula through the neck incision leaving the wires in place

• Remove 2-3mm of insulation from the abdominal end of the wires and tunnel into the abdominal muscle utilizing a 27g needle one at a time, ensuring the wires are close to each but do not touch

• Secure wires using 6-0 non-dissolvable sutures

• Close skin incisions with interrupted sutures

• Coil the wires extending from the next into a flat disc and suture to nape of neck to prevent disruption

• Prepare surgical area in accordance with institutional requirements.

• Clean and sterilize instruments

• Warm heating pad

• Check all equipment prior to starting

Prepare the mouse

• Anesthetize with 1.5% inhaled Isoflurane

• Shave right abdomen

• Clean exposed skin with Betadine

Surgical incision

• Make a ~ 1 cm skin incision in right lower abdomen above the inguinal region to expose the abdominal muscle sufficient to admit passage of the transmitter body

Transmitter Implantation

• Use blunt dissection to create a pocket in the right flank sufficient to house the transmitter. Take care to avoid making the pocket too large, which could result in seroma formation.

• Remove 2mm of insulation from each wire. Set aside insulation for later use.

• Using a 27 G needle, tunnel each wire individually through abdominal muscle. Wires should be placed closely together but should not touch

• Place insulation back on the exposed ends of each wire as they emerge from the muscle tissue and secure in place with 6-0 non-dissolvable sutures. Note: the insulation can be stretched with fine forceps to aid placement back into the wire.

• Suture the wires proximally to muscle entry to both secure the wires in place and to prevent moisture seepage into the transmitter.

• Close skin with either interrupted sutures or surgical staples

• Provide analgesia per institutional surgical protocol

• Administer 1ml of warm, sterile saline subcutaneously to mitigate dehydration

• Animals should be singly housed to prevent surgical site and EMG wire disruption prior to VMR experiment

• Lightly anesthetize mouse with Isoflurane

• If using wired VMR, take down coil by carefully cutting sutures and unspooling wire. Take care not to cut the wire

• Lubricate disposable gavage needle with Surgilube or similar and administer 100 uL water enema to remove fecal pellets

• Insert balloon catheter to depth of 2 cm and secure in place by taping tubing to animal tail

• Place mouse into broomenator style restrainer and allow to wake up

• Follow manufactures instructions for recording EMG and pressure tracings

• We use a NeuroLog NL100AK headstage, Band-Pass Filter (NL125/6), Pressure Amp (NL108A), and Extracellular Recording Amplifier (NL104A) feeding into Spike2 for our wired recordings and the Data Sciences International Ponemah system for our wireless recordings

• Program barostat (Distended Series IIR) to deliver sequential balloon inflations of 20, 40, 50, 60, 70, and 80 mmHg for 20 s each with a 2 m rest period in between distensions