Plasma levels of catechols after fasting in intact or adrenal-demedullated rats

We compared arterial plasma levels of catechols after a 24-h fast with levels after 24 h of an ad libitum diet in conscious rats. Epinephrine concentrations were significantly decreased after the fast; levels of norepinephrine, dopa, and dihydroxyphenylglycol were unaffected. Adrenal-demedullated rats had decreased levels of dopa regardless of dietary intake and lower levels of norepinephrine after fasting than during the usual diet. The results indicate that fasting decreases adrenomedullary activity in intact animals, with little or no effect on sympathoneural activity.