Energy balance following sympathetic denervation of brown adipose tissue.

The effects of sham, bilateral surgical denervation or excision of interscapular brown adipose tissue on body composition and energetic efficiency were studied in young CFLP mice kept at 25 degrees C and fed a laboratory stock diet. A preliminary experiment showed that 15 weeks following surgery, total body fat was increased by 42% in the denervated group and by 72% in the excised group while body protein was unchanged. In another 7-week energy balance experiment, body fat was also significantly higher by 15 and 18% in the denervated and excised group, respectively, but metabolizable energy intake was slightly lower than that of sham controls. Determination of energy expenditure both by the comparative carcass slaughter technique and by measurement of daily oxygen consumption showed that the metabolic rate was reduced in the denervated nd excised groups. The capacity for thermogenesis, as measured by an increase in oxygen consumption following injections of noradrenaline (600 micrograms/kg body weight) was similar in energetic efficiency, and indicates an important role of the sympathetic nervous system in the regulation of animal heat production by brown adipose tissue and in the overall control of thermogenesis.