Brand, Paul H., Nianning Qi, Patricia J. Metting, and Steven L. Britton. A self-powered constant infusion device for use in unrestrained rats. Am J Physiol Heart Circ Physiol 278: H2157–H2162, 2000.—We developed a device that delivers fluid through a catheter at a constant rate and can be used in conscious animals to solve a variety of problems. For example, this device can be used for delivering drugs and maintaining intravascular catheter patency. The device provides infusions at low flows (1.0–1.5 ml/day), so that experimental agents may be administered with minimal volume loading of the rat. Arterial and venous catheter patency is maintained by infusion of heparinized saline through indwelling catheters attached to the device. The catheters exit from the rat in the intrascapular area and are routed through a protective spring to the device, which is suspended above the cage. The catheters may be attached to pressure transducers, blood may be sampled, and injections or infusions may be made without disturbing the rat. Because the device is self-contained, it can be suspended by a fluid-free swivel that rotates through 360°, providing minimal restraint. The device has been used successfully to measure arterial and central venous blood pressures in two studies using rats.