Thermoregulation: effects of environmental temperature on turnover of hypothalamic norepinephrine.

The hypothesis that norepinephrine is a transmitter in the temperature regulating center of the hypothalamus is based on observations of changes in the rectal temperatures of animals after injections of norepinephrine into the hypothalamus. By introducing tritiated norepinephrine as a label into the endogenous norepinephrine stores in the brain and then measuring the disappearance of tritiated norepinephrine from discrete areas, one can monitor the activity of norepinephrine-containing neurons in those areas. In the rat exposed to heat, the turnover of endogenous norepinephrine appears to be increased selectively in the hypothalamus, whereas exposure to cold has no effect.