Effects of noradrenaline and propranolol on the thermoregulation in the acutely cold-exposed mice

Abstract

Abstract 1. Acute exposure to cold (30 minutes at − 5°C) significantly decreased the body temperature of mice acclimated either to 32°C or to 22°C, but not of mice acclimated to 5°C. Prior injection of noradrenaline (NA) did not improve the animals' ability to withstand cold exposure. Propranolol injection induced a significant decrease of body temperature in all mouse groups. 2. At the same time, the blood free fatty acid (FFA) level increased significantly in mice acclimated to 32°C or to 22°C. This effect was further stimulated by prior injection of NA. In cold-acclimated mice, no change in blood FFA level was measured. NA injection also had no effect. Propranolol injection lowered FFA level in all groups. 3. Acute exposure to cold induced a rapid output of glycogen by the liver of all groups and this was further increased by injection of propranolol. 4. Lipolytic and anti-lipolytic effects of NA and propranolol on the incubated interscapular brown adipose tissue correlated well to the lipolytic and anti-lipolytic effects seen in vivo . 5. The oxygen consumption of the interscapular brown adipose tissue of cold-acclimated mice was significantly more effective than in warm-acclimated mice. Only in cold-acclimated mice did NA have a stimulatory effect.