Thermogenesis in the marsupial Sminthopsis crassicaudata: effect of catecholamines and diet

The fat-tailed dunnart (Sminthopsis crassicaudata) is a small carnivorous m arsupial with detectable brown adipose tissue. In order to determine whethe r catecholamines and food intake increase thermogenesis in this species, we measured the response of oxygen consumption ((V) over dot O-2) to (i) intr aperitoneal noradrenaline (0.25-4.0 mg kg(-1)), and (ii) food intake. The e ffect of nutritional status and macronutrient composition of the diet on th e (V) over dot O-2 response to food intake was determined by feeding both n on-deprived and 24-h-food-deprived animals with either laboratory diet (1.0 1 Kcal g(-1) (4.2 KJ g(-1)), 20% fat) or live mealworms (Tenebrio molitor l arvae) (2.99 Kcal g(-1) (12.5 KJ g(-1)), 30% fat). Intraperitoneal injectio n of noradrenaline at doses of 0.25 and 0.5 mg kg(-1) increased (V) over do t O-2 by 14% and 31% respectively at 30 min (P less than or equal to 0.05), whereas noradrenaline at 2 and 4 mg kg(-1) decreased (V) over dot O-2 by 1 0% and 31% respectively (P less than or equal to 0.05). Following food inta ke, (V) over dot O-2 increased in both non-deprived (P i 0.05) and 24-h-foo d-deprived (P < 0.05) animals. While the magnitude of the increase in (V) o ver dot O-2 was similar in animals fed with either laboratory diet or mealw orms, both diets increased (V) over dot O-2 more in non-deprived than in 24 -h-food-deprived animals (P < 0.05). These results suggest that in S. crass icaudata (i) catecholamines increase thermogenesis and (ii) the magnitude o f diet-induced thermogenesis is dependent on both the nutritional status of the animal and the macronutrient composition of the diet.