Mice and rats were anesthetized with an isoflurane (1–3%)/oxygen vapor mixture and prepared with intravenous catheters. Briefly, the catheters consisted of a 6 cm (mice) or 12 cm (rats) length of silastic tubing fitted to guide cannula (Plastics One, Wallingford, CT) bent at a curved right angle and encased in dental acrylic. The catheter tubing was passed subcutaneously from the animal's back to the right jugular vein, and a 1 cm (mice) or 2.5 cm (rats) length of the catheter tip was inserted into the vein and tied with surgical silk suture. Catheters were flushed daily with physiological sterile saline solution (0.9% w/v) containing heparin (10–60 USP units/ml). Catheter integrity was tested with the ultra short-acting barbiturate anesthetic Brevital® (methohexital sodium, Eli Lilly, Indianapolis, IN).
