[hexxiiiz]

We actually have a bit of a schematic diagram already. It is well known that both dopamine and serotonin are largely produced by clusters of neurons in specific fore/mid-brain regions that then project out into the rest of the brain. The axions of these modulator neurons secrete the hormone, and it is known for both serotonin and dopamine (1) what receptors they bind to, (2) what transporters reuptake them into the presynaptic neurons, (3) what enzymes break them down. So the schematic of the system can be sketched out, and details of it, such as receptor functioning, can be determined pretty well in vitro. What we don't have is the timeseries data to properly parameterize this model. This research starts to provide this. You should check out research in pharmacology; there is a big hole for this and people are just guessing based on this schematic what the dynamics are.