Oral stimulation alters digestion of intragastric oil meals in rats

Rats were fed corn oil by gastric catheter, and plasma levels of triglycerides were measured 1-6 h later. In previous studies intragastric feeding of oil resulted in a more rapid rise in plasma triglycerides, followed by a more rapid fall, than oral feeding of the same amount of oil. In the present study administration of a small amount of oil or saccharin to the mouths of rats immediately before intragastric feeding prolonged the elevation in blood triglycerides 4 h later. This latter effect appeared only in rats having previous experience with oil paired with the taste. Oral stimulation with saccharin also increased the amount of fat remaining in the stomach 1 h after the intragastric meal. The amount of free fatty acids remaining in the stomach 1 h after intragastric feeding was not significantly influenced by oral stimulation, suggesting that lingual lipase is not responsible for the observed effects. These findings demonstrate that a taste which has been paired with fat intake can acquire the ability to influence the digestion of fat.