Acid flashbacks. Mine are fun.
Suddenly glad i've never used.
Ecstasy permanently changes your brain chemistry the very first time you used it.
Can't find anything to back this up, so link plz?
It certainly changes your brain chemistry when you take it - that's how it works - but AFAIK you need to use it on a long-term basis for it to actually make noticeable changes to your brain.
Should also point out that lots of things, including meditation, taking up exercise, falling in love etc can also permanently alter your brain structure and/or chemistry.
Let me google that for you. Granted, it doesn't say anything about "first time", but when you're dealing with neuroreceptor production and brain activity, change due to long-term behavior indicates smaller change with short-term behavior. So yes, taking ecstasy a single time would alter your brain chemistry, just likely not in an incredibly visible way. I will note, though, that the way ecstasy works is hardly normal change in brain activity; it forces neurons to dump their entire load of serotonin, creating the extreme happiness associated with it. Because of this, users tend to have much lower serotonin levels after coming down, putting them into an extreme depressive state. Repeated use "wears out" neurons, making it more difficult for your brain to bounce back, leaving you in much more depressive state than when you started using.
It can also cause psychosis in some individuals in shorter time periods. But yeah, equating mild shifts in neurotransmitter production to the sort of changes caused by drug abuse is sort of absurd.