The role of jejunal signals in the long-term regulation of food intake in the rat.

The significance of the upper small intestine in long-term regulation of food intake was investigated in pairs of parabiotic rats in which a 30 cm transected segment of each rat's intestine was sewn into continuity with the intestine of its partner. In this preparation, food eaten by one rat passes through its own stomach and 5 cm of its duodenum and then moves into the partner's intestine. The food traverses the 30 cm segment of the partner's intestine before returning to its own lower small intestine. All pairs were fed a liquid diet 11 hr/day. When the regular diet was diluted 1:1 with water, all rats showed a significant, nearly compensatory increase in their daily intake. In contrast, when only one rat in each pair was fed, thereby depriving it of intrajejunal input from its fasted partner, there was no significant increase in its food intake for about six days, followed by a gradual increase which was never fully compensatory as shown by continued loss of weight for the pair. Feeding rats could not be trained to notice the loss of intrajejunal input by making such loss coincident with a change in diet flavor. Jejunal satiety cues arising from a 30 cm segment, if they exist, do not seem to play a significant role in long-term regulation of food intake.