IACUC / LARC STANDARD PROCEDURES

GONADECTOMY IN RATS AND MICE

A. Ovariectomy

1. Weigh and anesthetize animal with doses of anesthetics recommended in standard procedures. Avertin and metofane are commonly used in mice while pentobarbital is used in rats.



2. Confirm that the animal shows a reduced respiratory rate and no response to gentle pinching of foot pad (see section on monitoring anesthesia). Shave both flanks of the animal. In the mouse, shaving is optional. Swab the shaved area with 70% ethanol. All instruments should be sterilized by dipping in 90% ethanol and then flaming in a Bunsen Burner or by other accepted methods of sterilization.



3. A 5mm, dorsal/ventral incision is made through the skin of the flank of the mouse below the muscles surrounding the spinal cord. The incision is centered between the bottom of the rib cage and the front of the hind limb. In the rat, a 10mm incision is placed in a similar fashion. The skin is separated from the underlying muscle.



4. Before making the incision through the muscle overlying the ovary, confirm the location of the ovarian fat pad which is sometimes visible under the muscle. Rather than cutting the muscle, insert the tip of double sharp iridectomy scissors just through the muscle layer, and separate the muscle fibers by opening the scissors in a dorsal ventral direction.



5. Hold the edge of the incision open with a small rat tooth forceps and pull the ovary through the incision with a blunt forceps by grasping the fat pad surrounding it.



6. Place a mosquito hemostat at the boundary between the oviduct and uterus, and place a ligature just below the hemostat. After removing the ovary and oviduct with a scissors, release the hemostat and make sure no bleeding occurs. Return the ovary to the abdominal cavity, and suture the muscle layer if necessary. Close the skin incision with wound clips.



7. Turn the animal over and repeat the procedure on the other side.



8. Return the animal to its cage and leave undisturbed in a warm, quiet place. Monitor the animal continually until it is completely recovered from anesthesia. If clear signs of pain, acute discomfort, or adverse reaction to the drug are apparent (e.g., convulsions, respiratory distress), the animal should be euthanized. Following recovery, the animal should be monitored daily for one week for signs of infection or persistent problems, in which case the animal should be euthanized.

B. Orchidectomy

1. Weigh and anesthetize animal with doses of anesthetics recommended in standard procedures. Avertin and metofane are commonly used in mice while pentobarbital is used in rats.



2. Confirm that the animal shows a reduced respiratory rate and no response to gentle pinching of food pad (see Section 2-E on monitoring anesthesia). Shave the abdominal region of the animal. (In the mouse, shaving is optional). Swab the shaved area with 70% ethanol. All instruments should be sterilized by dipping in 90% ethanol and then flaming in a Bunsen burner or by other accepted methods of sterilization.



3. Make a 1.5 cm, transverse incision in the skin at a point level with the top of the legs. Separate the skin from the muscle layer. See diagram provided for the standard procedure for vasectomy. Make a similar incision through the abdominal muscle.



4. Both testes can be reached through the same incision. Localize the testicular fat pad on the left side and pull it through the incision using a blunt forceps. Place a hemostat below the testes and epididymis across the testicular cord (contains blood vessels and vas deferens). Place a ligature below the hemostat and remove the testes and epididymis with a scissors. Repeat for right testes.



5. Suture the abdominal wall with 2-3 stitches and repeat for skin incision. (Wound clips can be used for skin incision, but sutures are recommended because the body clip can affect sexual proclivity).



6. Return the animal to its cage and leave undisturbed in a warm, quiet place. Monitor the animal continually until it is completely recovered from anesthesia. If clear signs of pain, acute discomfort, or adverse reaction to the drug are apparent (e.g., convulsions), the animal should be euthanized. Following recovery, the animal should be monitored daily for one week for signs of infection or persistent problems, in which case the animal should be euthanized.