Serotonin metabolism in liver disease.

Serotonin, (5-hydroxytryptamine, 5-HT, enteramine) is widely distributed in animal tissues and has been shown to have marked pharmacologic effects upon the gastrointestinal tract and cardiovascular system (1-4). Indirect evidence suggests that serotonin may play an important role in cerebral function, but, as yet, no direct connection has been established between serotonin and cerebral disease (5). Previous reports (6) and personal observations have shown a low normal excretion of 5-hydroxyindoleacetic acid, the end product of serotonin metabolism, in liver disease. The precursor of the serotonin of brain is apparently 5-hydroxytryptophan. In view of these facts, the possibility that severe liver disease by, in some way, affecting the production of 5-hydroxytryptophan, might alter brain function, was investigated by the following series of experiments.'