Fascinating stuff - a great find, GF, and also great that a prestigious journal like Nature is publishing a topic like this. And OPen Access, too.
The presence of compounds such as - in particular - hordenine, N-methyl
tyramine (not "thyramine [sic]), N-methylmescaline and trichocerine in greater concentration than mescaline goes a long way towards explaining the more highly stimulating nature reported for T. terscheckii. Hordenine is known to be quite stimulating and it seems likely that the other compounds would synergise with it at a metabolic level at the very least. I wonder if perhaps they competitively inhibit the breakdown of dopamine too; there is about as much N-methyl mescaline as there is dopamine and the trichocerine isn't too far behind.
It'll take me a bit more background reading to grasp the implications of any genetic adaptations in populations with a history of Trichocereus cactus use, but already I do wonder if they might serve to smooth out some of the subjective effects.
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli