Does 4-fluoroamphetamine have action @ the 5ht2b receptor? It definitely has mdma-like empathogenic effects for me..
but then again if something releases serotonin.. the serotonin will activate the 5ht2b receptor anyway, maybe not as strongly or specifically..
I'm curious though, it still doesn't explain how mdma and mda aren't cross tolerant... in the study they dosed MDMA to build tolerance and then checked if MDA still worked, but I wonder if MDA was used first to build tolerance would MDMA still work after? To me it seems like that would be important information to have before concluding "that MDMA and MDA are not cross-tolerant," since it would give insight to their differences.
For example, if MDA dosed to max tolerance stopped MDMA from working you could conclude that MDA has additional effects apart from MDMA that allow it to continue to work, rather than them working through completely different mechanisms.