Intragastric injections of partially digested triglyceride suppress feeding in the rat

The 30 min intake of a 50% corn oil emulsion was measured in 12 hr fasted Sprague-Dawley rats equipped with gastric tubes. When the subjects were given 5 ml intragastric injections of normal saline or of the same oil emulsion they drank by mouth their voluntary intake was unaffected. However, when they were injected with oil emulsion that had been previously ingested by donor subjects, they decreased their feeding significantly. These results suggest that the putative satiety receptors are not stimulated by undigested corn oil triglycerides but by a product of their digestion. This factor appears to be present in the oily rather than the aqueous fraction of the digested oil because when these fractions were given separately only the oily fraction induced inhibition of feeding. Finally, intragastric injections of predigested oil failed to act as an unconditioned stimulus in the development of taste aversions to neutral flavors. This suggests that the reductions in eating observed were not the product of malaise or discomfort.