Chronic arterial and venous catheterization of conscious, unrestrained rats

A method is described for implanting arterial and venous cannulas in rats that requires only minor surgery. Catheters are introduced into the abdominal aorta through the ventral tail artery and into the vena cava through a lateral tail vein. The wounds are covered with an acrylic cuff and the catheters are brought out through a stainless steel spiral connected to the cuff and then attached to top of a metabolism cage used to house the rat. This method makes possible continuous access to the catheters in undisturbed, mobile animals. Using this model we compared mean arterial pressure, heart rate, plasma renin activity, and plasma catecholamine levels in freely moving Long-Evans rats and in Brattleboro homozygous rats.