Production of satiety with small intraduodenal infusions in the rat

Rats equipped with chronic intragastric and intraduodenal catheters received small infusions of various solutions through one catheter during spontaneous meals. Regardless of which compartment or which solution was infused, the animals maintained a constant daily nutrient intake. However, all hypertonic solutions reduced mean meal size and increased the frequency of feeding when injected intraduodenally, while only nutritive solutions reduced mean meal size when infused intragastically. Water ingestion varied with the effective osmotic pressure of the injected solutions, but there were no differences in water ingestion as a function of the compartment infused. These data suggest both the presence of a duodenal satiety mechanism and the validity of interpreting the meal patterns of vagotomized rats eating a liquid diet as resulting from the rapid emptying of the diet into the duodenum.