Insulin was injected directly into the medial amygdala (AMYG) of rabbits, and changes in hepatic acetate metabolism were studied. The injection of 50 microU insulin into the AMYG decreased the rates of 14C transfer from 14C-1-acetate into CO2 and cholesterol ester, and increased those into free cholesterol and phospholipids. But after insulin injection into parietal cortex of intact rabbits and into the AMYG of rabbits with lesions of stria terminalis (ST), hepatic acetate metabolism did not differ from that of the control rabbits, which received saline injection into the same brain regions. These observations support the hypothesis that the AMYG is a part of insulin-sensitive brain regulator system in the hepatic acetate metabolism.