2-Methyl-5-hydroxytryptamine
2-Methyl-5-hydroxytryptamine (2-methylserotonin, 2-methyl-5-HT) is a tryptamine derivative closely related to the neurotransmitter serotonin which acts as a moderately selective full agonist at the 5-HT3 receptor.
Source: Wikipedia — 2-Methyl-5-hydroxytryptamine (CC BY-SA 4.0)