Intestinal Serotonin
In the 1930s, serotonin was identified in the intestine, and
thus termed ‘‘enteramine.’’ This was subsequently found
to be the same substance extracted from blood samples
in the 1940s and termed serotonin. In the 1950s, serotonin
was identified as a principal monoamine neurotransmitter
of the gastrointestinal tract. Multiple lines of evidence
support its role as a neurotransmitter within the enteric
nervous system. The myenteric and submucosal plexi
contain tryptophan hydroxylase and display a capacity
to synthesize serotonin from L-tryptophan (Gershon and
Dreyfus, 1980). Moreover, serotonin is released upon
electrical stimulation of the enteric nervous system. The
functional significance of enteric nervous system serotonin
is indicated by the impairment of intestinal motility by
the serotonergic neurotoxin 5,7-DHT