Example IACUC Protocol
Mice - EMG and headcap, headplate, and ground pin implantation surgery
This surgery will be conducted in accordance with IACUC policy on aseptic survival surgeries in rodents. Mice do not undergo multiple surgeries; this procedure is only performed on mice that have not undergone any other surgical procedure.
Electromyographic (EMG) recording arrays will be chronically implanted into the forelimb or the hindlimb and a head cap, head plate, and ground pin will be placed on the skull. The EMG arrays are made out of polyimide, a widely used biocompatible polymer that is flexible and allows our arrays to lie flat subcutaneously without the need for large disruptions of tissue. The arrays will be sterilized by autoclave prior to surgery and handled with sterile instruments. The metal groundpin, headplate, and head cap will also be sterilized using an autoclave.
The surgical site and head will be prepared as described above. First, the ground pin, head cap, and head plate are placed on the head. An incision is made on the midline of the scalp, from just above the eyes to the back of the head, and the skin is propped open using skin retractors. All tissue is cleaned off the skull using a scalpel blade. A dental drill is used to create a small hole, which exposes the dura, in the skull. A ground pin placed in this hole will be in contact with the dura and will be used as a ground for the electrodes. The ground pin is secured in place with dental cement. The headplate, which is used for head fixation, is secured behind the ground pin on the skull and covered by the headcap. To improve adhesion, we may score the skull with a scalpel and/or dry the skull with 3% peroxide on a sterile swab. Both the head plate and head cap are secured in place with dental cement.
To implant the array, a 5mm skin incision is made near the dorsomedial area of the neck, and the array is threaded subcutaneously to the area of the shoulder complex. Forceps will be used to clear subcutaneous fascia and connective tissue to push the array as close to the shoulder as possible. Small 5mm incisions are made above the muscles that will be recorded in order to place and secure the arrays. The arrays lie subcutaneously flat on top of muscle and fascia from the dorsomedial area of the neck along the shoulder complex and out to the major muscle groups of the forelimb (i.e., biceps, triceps, traps). The small incisions over the muscles are sutured closed using 11-0 sterile monofilament sutures.
Arrays will also be implanted intramuscularly using protocols similar to previously established procedures to implant wire electrodes intramuscularly. Arrays are secured to a 25G needle that is used to thread the array through muscle tissue. The array has a profile smaller than the needle to help reduce tissue irritation. Once inserted, intramuscular arrays are secured in place using sterile 10-0 sutures on both sides of the insertion in order to ensure the array does not shift for the duration of implantation.
When the arrays are threaded under the skin, the connector that is secured in place with dental cement remains exposed to be inserted into a connector for the recording. The 5mm skin incision is closed using 8-0 sterile monofilament sutures
Arrays within animals will be briefly tested while the animal is still anesthetized to ensure correct placement of the arrays.
Mice - Jaw muscle reflex
Mice will undergo terminal surgery to provide acute recordings of jaw muscle activity. Animals will remain under anesthesia in a stereotaxic frame for the duration of this procedure, which will not last longer than two hours. A broad rectangle incision will expose the temporalis muscle and allow for implantation of the electrode array in the jaw muscle. Using a cotton swab, experimenters will gently prod the lower jaw in various directions. This will generate reflexive movements driven by activity in the temporalis as the jaw returns to its base position. The EMG activity will be continuously recorded using Intan hardware and software. In addition, the behavior will be recorded on video cameras, which will be analyzed offline. Afterwards, the animal will be euthanized.
Mice - EMG testing during surgical recovery
During recovery from EMG surgery but before behavioral testing, we need to check the response of our EMG arrays. These tests are essential to see how the EMG signal evolves during animal healing, and allow us to make modification to our array design.
Immediately after animals have recovered from surgery and are fully awake, we will briefly record EMG activity while performing a non-painful toe pitch. To do so, we will plug the connector on the animal's headcap into a tethered wire connected to our EMG-recording computer. Care will be taken to not touch the recovering limb and recording will be immediately stopped if the animal appears in distress. This recording will last a maximum of 10 minutes.
During wound healing, we will perform a daily recording while animals' surgical wounds heal. These will be performed either in the animal's home cage or on a freely spinning treadmill/running wheel. Again, animals will have the headcap connected to a tether wire and EMG activity will be monitored while they move freely in their cage or on the treadmill/running wheel. This recording will not exceed 10 minutes. Care will be taken to not touch the recovering limb and recording will be immediately stopped if the animal appears in distress. These recording sessions will continue until wound healing has completed and the mouse may move into behavioral testing.