INSULIN IS A PRANDIAL SATIETY HORMONE

The present study assessed meal-contingent insulin effects on spontane ous meal patterns. Rats, trained to lever press for daily food require ments, showed stable meal patterns and were then implanted with hepati c-portal catheters. Once again stable in ingestion, animals received e ither physiological saline or vehicle plus 1 or 2 mU of regular, short -acting insulin beginning at 10 pellets into each initiated meal (whic h was the chosen minimum meal size definition). All meals during that day were then infused with the same solution and comparisons were made within animals (across days) only. Insulin reduced the size of sponta neous meals at both 1 mU (p < .01) and 2 mU doses (p < .001). No other meal parameters were significantly affected. In a complementary study , rats trained to lever press showed increases in meal size when ''rec overing from'' a diazeoxide-adulterated diet (diazeoxide has been show n to limit insulin release). Thus, when insulin is increased during sp ontaneously taken meals, those meals are reduced in size and drugs whi ch block insulin release, increase the size of meals; we assert insuli n is a prandial satiety hormone which likely reduced feeding by increa sing glucose uptake into peripheral tissue.