Effects of beacon administration on energy expenditure and substrate utilisation in Psammomys obesus (Israeli sand rats)

OBJECTIVE: To investigate whether beacon administration affects substrate u tilisation, physical activity levels or energy expenditure in Psammomys obe sus. DESIGN: Pairs of age- and sex-matched Psammomys obesus were randomly assign ed to either beacon-treated (15 mug/day for 7 days (i.c.v.)) or control (i. c.v. saline) groups. MEASUREMENTS: Indirect calorimetry on day 0 and day 7 to measure oxygen con sumption and carbon dioxide production, which were used to calculate fat ox idation, carbohydrate oxidation and total energy expenditure. Physical acti vity in the calorimeter was measured using an infrared beam system. Food in take and body weight were measured daily. RESULTS: The administration of beacon significantly increased body weight c ompared to saline-treated control animals. This body weight gain was primar ily due to increased body fat content. Average daily food intake tended to be higher in beacon-treated Psammomys obesus, but no effect of beacon admin istration on substrate oxidation, activity or energy expenditure was detect ed. CONCLUSION: The effects of beacon on body weight are due to increased food intake, with no detectable effect on nutrient partitioning, physical activi ty or energy expenditure.