The influence of centrally applied noradrenaline on shivering and body temperature in the pigeon.

1. Noradrenaline (NA) was injected in a volume of 1.0 mul. through chronically implanted cannula into the hypothalamus of the unanaesthetized pigeon.2. In doses of 1-15 mug NA caused complete inhibition of shivering of dose-dependent duration. Histological mapping of the brain showed that NA was exerting its inhibitor action in the region above the optic chiasma bordering on the posterior hypothalamus and the anterior preoptic nucleus.3. At low ambient temperature, the NA induced inhibition of the cold tremor caused a fall of core temperature which lasted as long as shivering was inhibited. Shivering induced by local cooling of the spinal cord, and by the combined cooling of the skin and the spinal cord, was likewise inhibited by the cerebral application of NA. There was no evidence of an adjustment of the temperature set-point by NA.4. A rapid rise in skin temperature of the unfeathered feet, whenever NA was injected indicated a reduction in peripheral vasomotor tone.