Are there density maps for specific neurotransmitters that I can have a look at?
By density map I mean a map that indicates
how the somata of X-releasing neurons are distributed
how the somata of X-receiving neurons are distributed
how X-synapses are distributed (typically near to X-receiving neurons' somata but possibly far away from X-releasing neurons' somata)
in short: the density map of a neurotransmitter system (or pathway)
Such density maps would possibly not depict the results of any immediate measurement but be the result of some data analysis.
I guess to know such maps would help to predict and minimize side-effects of psychoactive drugs, mainly when thinking about applying them locally - but that's the topic of another question.