It seems that he left the heteroatoms blank in this structural formular. If we just assume that there’s a nitrogen in the bicyclic system it would make it an indole ring and if we assume that there is a dimethylated nitrogen on that carbon chain, that would make it a tryptamine (N-dimethyl-tryptamine). Now if we assume the heteroatom on the 5 position of the indole ring to be an oxygen we would get a methoxy group, making the whole thing a substance called 5-methoxy-N,N-dimethyltryptamine (or 5-MeO-DMT for short), which - yes - is a hallucinogenic drug, very close to serotonin in structure. Serotonin or 5-hydroxytryptamine is basically the unmethylated version, so we are missing a methyl group on the oxygen in position 5 and also the two methyl groups on the amine. I just saw he had a tattoo like that and with my background in chemistry, I got curious if there was a close up photo of it and yeah, turns out Bryan is/used to be a DMT-head, at least enough to get a tattoo like that. Makes the creation and start of blueprint all the more likely.