Metabolic effects of chronic infusions of epinephrine and norepinephrine in rats

Chronic infusions of epinephrine, norepinephrine, or vehicle were performed in adult male rats by means of subcutaneous implanted osmotic minipumps (ALZET). The calculated dose was 180 ng/min during 7-8 days. Daily food intake and body weight were measured during this period and also 7 days before and 5 days after it. During the period of infusion, norepinephrine stopped body weight gain while epinephrine-infused rats gained weight at the same rate as controls. Once the infusion period was finished, epinephrine-infused rats gained more weight than controls, while norepinephrine-infused rats just returned to the slope of weight gain of the controls. In no group did food intake change. In a second experiment, similar infusions were carried out in other rats on the same schedule; body temperature, glycemia, and serum insulin and triiodothyronine were measured. Epinephrine infusion significantly elevated glycemia and triiodothyronine, whereas norepinephrine infusion increased temperature and serum insulin. The results obtained by chronic administration of the catecholamines support the concept of a disassociation of adrenomedullary and sympathetic nervous system metabolic effects.