Seotonin (5-HT, 5-hydroxytryptamine) is not the same as 5-HTP (5-hydroxytryptophan).
I presume you know the 5-HT is in the stinging hairs, so don't go rubbing it off with bare hands!
Interesting tryptamines have been found in the seeds and foliage, but bear in mind that the seeds contain large amounts of L-DOPA, and the yields of the tryptamines are not known from seeds (and roots). Known levels of tryptamines in leaves are low, but there was one report in an old Entheogen Review of someone smoking the leaves after having taken an MAOI and getting mild psychedelic effects.