Serotonin: Synthesis and Release from the Myenteric Plexus of the Mouse Intestine

After injection of its radioactive precursor, 5-hydroxytryptophan, radioactive serotonin was biosynthesized and bound in the myenteric plexus of the mouse intestine. Addition of nonradioactive serotonin to preparations in vitro caused a net release of radioactive serotonin from the plexus. This release appeared to result from activity in the intramural nervous system of the intestine. A neurotransmitter role between sensory and motor neurons in the peristaltic reflex pathway is suggested as a working hypothesis to explain the action of serotonin.