Abstract

The fat-tailed dunnart (Sminthopsis crassicaudata) is a small carnivorous marsupial with detectable brown adipose tissue. In order to determine whether catecholamines and food intake increase thermogenesis in this species, we measured the response of oxygen consumption (Vo₂) to (i) intraperitoneal noradrenaline (0.25–4.0 mg kg^-1), and (ii) food intake. The effect of nutritional status and macronutrient composition of the diet on the Vo₂ response to food intake was determined by feeding both non-deprived and 24-h-food-deprived animals with either laboratory diet (1.01 Kcal g^-1 (4.2 KJ g^-1), 20% fat) or live mealworms (Tenebrio molitor larvae) (2.99 Kcal g^-1 (12.5 KJ g^-1), 30% fat). Intraperitoneal injection of noradrenaline at doses of 0.25 and 0.5 mg kg^-1 increased Vo₂ by 14% and 31% respectively at 30 min (P ≤ 0.05), whereas noradrenaline at 2 and 4 mg kg^-1 decreased Vo₂ by 10% and 31% respectively (P ≤ 0.05). Following food intake, Vo₂ increased in both non-deprived (P < 0.05) and 24-h-food-deprived (P < 0.05) animals. While the magnitude of the increase in Vo₂ was similar in animals fed with either laboratory diet or mealworms, both diets increased Vo₂ more in non-deprived than in 24-h-food-deprived animals (P < 0.05). These results suggest that in S. crassicaudata (i) catecholamines increase thermogenesis and (ii) the magnitude of diet-induced thermogenesis is dependent on both the nutritional status of the animal and the macronutrient composition of the diet.