brilliant - well written with some dense material. I tend to glaze over when I start to read about receptors and anything microbiology really, but you concisely presented a good biological puzzle.

I'm totally naive to drug biology, but this mystery makes me imagine that there's a whole other mediating level of drug effects... not what receptors they bind to, but how they enter the brain having an effect in and of itself, or how they disrupt other neurotransmitters.