Technique for performance and evaluation of parapharyngeal hypophysectomy in mice

Mice at our institution were hypophysectomized to evaluate the effects of growth hormone on the expression of a transfected human factor IX gene. The hypophysectomy was performed in-house by using a parapharyngeal approach modified from previously published surgical techniques. Modifications included: 1) choice of ketamine-xylazine and isoflurane for anesthesia, with butorphanol for postoperative analgesia; 2) use of a V-trough for positioning mice correctly and consistently; 3) selection of increasing sizes of dental burrs to create a foramen in the cranial base through which the pituitary gland was removed; and 4) disuse of a tracheotomy for airway patency. In addition, verification of successful gland removal was assessed by measuring major urinary protein (MUP) in the urine; presence of MUP indicated incomplete hypophysectomy. This assessment enabled antemortem determination of surgical success by using a single urine collection. Each of these modifications contributed to the success of the surgical procedure. We had a safe and reliable anesthetic regimen, consistent positioning of the surgical patient, and smooth and rapid penetration of the cranium. In our experience, the tracheotomy described in previous techniques was unnecessary, as the mice tolerated brief periods of apnea (approximately 5 sec maximum) while the trachea was retracted. Here we seek to provide details that will assist those interested in learning this technique and that will reduce the number of mice needed for practice. Other applications include a method of evaluating the production of growth hormone without euthanizing the animal.