[Basal metabolism: definition and apparatus for its measurement].

The " Metabolisme de Fond" (MF) is defined as the energy expenditure of the whole body cells, except for the energy devoted to the locomotor activity. The continuous measurement of the MF is performed in the free moving rat using a computer-controlled open circuitry calorimeter. This system provides simultaneous measurement of the metabolic parameters (oxygen, carbon-dioxide, respiratory quotient) as well as the quantification of the behavioral parameters (food intake, locomotor activity, sleep). The measurement of the MF is based on the calculation of the slope of the curve linking the relative changes in the intensity of respectively locomotor activity and total metabolism. Such a computation of the MF requires the precise analysis and the subsequent mathematical correction of the physical phenomena occurring in an open circuitry calorimeter. Indeed the instantaneous electrical signal of locomotor activity is recorded before the delayed and distorted corresponding increase in the energetic metabolism which must be corrected. In conclusion, the method described here allows the direct determination of quick MF modifications in the freely behaving rat.