Amaranthian

It seems like the drugs which cause the cellular transporters to go from suck to blow and thereby flooding the synaptic cleft and overstimulating the nerve cells of the "reward" pathway are the most addictive substances. Both dopamine and serotonin can have those results, depending on the drug involved. So it would seem that addiction is more a function of the drug's molecular structure and it's affect on the nerve receptors than which neurotransmitter is involved.

Also, super cute mousies!

Usually it isn't enough to simply flood the pleasure centers with a dopamine to cause addiction; some of the most addictive drugs are known as Selective Serotonin Reuptake Inhibitors. In essence what happens is that you become happy, Serotonin is released and begins to act on your pleasure centers, and then the drug prevents your brain from "mopping up", or reuptaking, the rest of the serotonin, making your pleasure centers flooded for a long period of time.

The addiction comes when your brain adjusts to the fact that it's gotten so much serotonin, and starts producing less serotonin when you're happy, anticipating the same level of it to hit the pleasure centers. Since this is a much lower level, if you don't use an SSRI, you end up feeling depressed, with the only solution being to take an SSRI to produce even normal levels of Serotonin in your pleasure centers. Ta-daaaa, chemical addiction!

I flooded your mom's pleasure center last night.

haha, nicely worded guys