In situ recording of rat heart contractility devoid of respiratory artifacts

A device was constructed for obtaining the cardiac force of contraction in the rat in situ. The devices was constructed from heat-resistant glass tubing that was opened to form a concave channel. The channel was notched and cup-shaped at one end. The apparatus was positioned around the heart to isolate it from lung or diaphragmatic tissue movement. The procedure was rapid, simple, inexpensive and free of respiratory artifacts. The method was an improvement over the more common in vitro recording techniques, since the heart had an intact nerve and blood supply. The method allowed quantitation of changes in the force of contraction, blood pressure and heart rate following the administration of acetylcholine, epinephrine, potassium chloride and barium chloride.