<<Disclaimer: Verify this information before applying it to your situation.>>
Here is a description for Serotin, don't know if this is what you are looking
for: A chemical, 5-hydroxytryptamine (5-HT), present in platelets,
gastrointestinal mucosa, mast cells, and carcinoid tumors. Serotonin is a
potent vasoconstrictor. It is also a neurotransmitter in the central nervous
system and is important in sleep-waking cycles. Are you more interested in
looking for information on carcinoid syndrome?
Hope this helps you. Good luck.
Clelia