The effect of diet on the 5-hydroxytryptamine content of the small intestine and other organs in rats and mice.

In rats, a diet of meat or liver caused a rise in the amount of 5-hydroxytryptamine in the small intestine, an increase in the weight of the intestine and a 10-fold increase in anaerobic bacteria in the rectum. A diet containing added tryptophan did not affect tissue levels of 5-hydroxytryptamine in rats, but in mice there was a rise of 5-hydroxytryptamine in various tissues. The significance of these findings is discussed together with the possible role of intestinal bacteria in mediating the effects caused by a meat diet. No change was observed in the 5-hydroxytryptamine content of brain or in the distribution of argentaffin cells in the jejunum as a result of these diets.