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.
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