The article pointed to says:

"Our data suggest that dopamine is released in very specific locations, with incredible spatial precision and speed, whereas before it was thought that dopamine was slowly and promiscuously secreted."

I always thought that this was likely because:

- taking levodopa, which is metabolized into dopamine, never gives a complete relief from the symptoms of PD (though for some people it does an excellent job for a number of years);

- levodopa gives better relief in the early years of the illness when there are still large numbers of dopaminergic neurons present. Not only do these produce dopamine, but they also store dopamine in vesicles. The indirect access to exogenously sourced dopamine via existing vesicles gives better relief than having dopamine spread out across the whole brain.

John