Implantation of Radiotelemetry Transmitters Yielding Data on ECG, Heart Rate, Core Body Temperature and Activity in Free-moving Laboratory Mice

The overall goal of this procedure is to implant a telemetry transmitter used for continuous measurements of core body temperature, locomotor activities, and bio potential from which heart rate, heart rate variability, and PQ and QT intervals can be established in free moving untethered mice. This is accomplished by first preparing the mouse for implantation a few days before surgery. Next, the operating environment instruments and the telemetric transmitter are prepared.

Then the telemetric transmitter is surgically implanted into the mouse. Finally, postoperative care is administered to the animal to warrant recovery and survival of the animal. Ultimately, the results show the impact of manifold biomedical experiments and genetic modifications on short-term and long-term heart rate, heart rate variability, PQ and QT intervals, core body temperature and locomotor activity, as well as on the circadian rhythm of these parameters through telemetric measurements in free moving mice.

The main advantage of telemetry over existing methods like measurements in restraint, tethered, or even ized animals, is that accurate data can be obtained over short or even long-term time periods in unrestrained, freely moving mice On the day of implantation, the telemetric transmitter is prepared under a laminar flow hood on a disinfected bench under aseptic conditions, using autoclave instruments and sterilized materials. To begin, remove the transmitters from their sterile package and using scissors shorten the leads to a length appropriate for the size of the mouse. For most adult mice, the red electrode can be shortened to about 42 millimeters and the white or colorless electrode to a length of about 55 millimeters.

Remove about 20 millimeters of insulation tubing from the distal part of the red electrode and 10 millimeters from the white or colorless electrode. Form the distal parts of each electrode into a loop by fixing the ends with thin silk sutures. Place the transmitter in warm, sterile saline, ready for implantation on the day prior to implantation.

Prepare the mouse by anesthetizing it in a perspex chamber with 8%cevo fluorine. When it has lost its writing reflex, attach a nose cone with three to 4%cevo fluorine.Clip. Shave the hair on the anterior neck and abdomen.

Allow the animal to awaken and return it to its home cage the next day after administering analgesia and anesthetizing the mouse, transfer it to a warm bath heated surface in the surgical area. Apply ointment to the mouse's eyes and maintain anesthesia using a nose mask and three to 4%seva fluorine. Please see the written protocol for further details.

Hails disinfect the previously shaved skin of the anterior neck and abdominal region of the mouse. Then make a one to 1.5 centimeter long incision in the skin from the lower thorax along the midline of the abdomen. Make a small incision in the longitudinal direction at the anterior neck and tunnel the negative lead of the transmitter subcutaneously from the thorax to the neck.

Prepare the skin and underlying tissue to make space for the fixation of the wire loop of the electrode. Fix the wire loop between the muscles located to the right of the trachea using two thin silk sutures. Then close the wound in the neck in layers with six dash O Vicryl sutures.

Open the abdominal wall at the lan alba and place the telemetric transmitter into the abdominal cavity. Suture the wire loop of the positive electrode to the xiphoid process with silk sutures so that it lies between the liver and the diaphragm in the upper left abdominal region. To prevent infection and supply fluid, inject a mixture of sul doin and trimethoprim and saline into the abdominal cavity and close the abdominal skin for pain treatment subcutaneously.

Administer 0.1 milligrams per kilogram bup, ine, and allow the animal to recover on the warm surface of the workbench for two hours. The animals are closely monitored and recovery support is provided for four to 10 days following the surgery as outlined in the written protocol. 10 days after surgery, return the animals to the mouse colony for at least four weeks of normal social interaction.

To initiate data collection, touch the animal with a magnet. This will switch on the transmitter. A data exchange matrix collects and sends data signals to the computer either for a specific length of time at regular intervals or continuously, and saves the data on the computer's hard drive because the range and the quality of the emitted signal depends strongly on the material composition of the cage and surrounding equipment.

Place the receiver plate as close to the animal as possible, for example, under the animal's cage. Use the data quest, a RT software to coordinate the detection, collection, analysis, and graphical presentation of signals from one or more animals. Check that the configuration of the recording and data transmission system is correct by taking real time measurements in continuous sampling mode.

After the data has been gathered and stored plot list and analyze them for a variety of different parameters such as heart rate, heart rate variability, body temperature, and locomotor activity using the analysis program, a raw printout of one lead ECG curves from a conscious mouse and of the same animal under inhalation anesthesia with cevo fluorine is shown here. Heart rate is calculated automatically by the telemetry system. The three second sequence recorded under anesthesia indicates a heart rate of 440 beats per minute.

The curve recorded in the conscious mouse shows a heart rate of 660 beats per minute, which falls within the expected range for heart rate. During moderate physical activities such as grooming or eating here, heart rate, core body temperature and locomotor activity were measured from three mice with differing bodily conditions while housed individually in their home cages without any disturbances. Heart rate was recorded for 30 seconds every five minutes.

Core body temperature was sampled for 10 seconds every five minutes, and locomotor activity was recorded continuously and stored at five minute intervals. The healthy mouse shows a clear circadian rhythm with normal increases in physiological values and locomotor activity behavior during the dark phase. In contrast, after major surgery, heart rate increased, particularly in the daylight phase and locomotor activity is depressed.

The third mouse suffered from chronic tumor disease. Its circadian rhythm of heart rate and core body temperature appears flattened and locomotor activity is diminished. In this experiment, 16 mice were subjected to 50 minutes of isof fluorine or cevo fluorine, anesthesia, and the long-term impact of anesthetics on heart rate, core body temperature, and locomotor activity was compared means of the telemetric Values for each animal were calculated separately for night and daytime phases.

Normal values were calculated as the means for the three days prior to anesthesia. The delta values are the comparisons of the dark and light values to the normal values. Once mastered surgery can be done in 35 to 45 minutes while attempting this procedure, it is important to keep in mind to maintain adequate anesthesia, administer effective analgesics, prevent infections, and supply fluid.

After watching this video, you should have a good understanding of how to implant this telemetric transmitter and how to obtain reliable measurements of physiological values like heart rate or cold body temperature in laboratory mice.