TREADMILL CHAMBER FOR STUDIES OF RESPIRATORY GAS-EXCHANGE IN THE RAT DURING EXERCISE

A treadmill for studying gas exchange in small mammals during exercise is presented. The system consists of a motor-driven running mat enclo sed in a gastight chamber that receives a measured flow of air from a compressed air cylinder. The gas flow and temperature, pressure and in stantaneous gas composition of the chamber (oxygen, carbon dioxide and water) are measured continuously and the data are computed to include the effects on chamber atmosphere of the rat activity either running or at rest. The system is completed with a shock delivery grid that st imulates the rat to run. The calculations are based on the changes in the composition of the gas in the chamber (constantly stirred by a sma ll electric fan) induced by the rat instead of relying on the alterati ons induced in the outflowing gas. The consumption of oxygen, and prod uction of carbon dioxide and water by the rat are computed in real tim e, giving a very fast response to physiological change induced by exer cise. The chamber is custom-made from an aluminium block and a plexigl ass lid; all other components are available commercially. The system, as described, allows for a detailed analysis of respiratory gas (and w ater) exchange by rats under varying exercise conditions, there is pra ctically no rime lag between changes in respiratory gases and the dete ction of these changes, and the buffering effect of the chamber size i s practically eliminated because of the calculation approach used.