FAEFHI
FAEFHI, also known as 4--5-hydroxyindole, is a serotonin [receptor modulator] of the indole group related to serotonin and other tryptamines. It is a positional isomer of serotonin in which the ethylamine side chain at the 3 position of the indole ring [system (chemistry)|ring system] has been moved to the 4 position. FAEFHI can also be thought of as a greatly simplified analogue of LSD and hence partial ergoline. Although FAEFHI shows significant affinity for serotonin receptors, it had much lower affinity than serotonin or tryptamine. In addition, it did not show serotonin-like activity even at very high concentrations in vitro. FAEFHI was first described in the scientific literature by 1984.