STUDY: Caffeine increases striatal dopamine D2/D3 receptor availability in the human brainhttps://www.ncbi.nlm.nih.gov/pmc/articles/PMC4462609/
DA = dopamine.
Striatum = central reward processing region of the larger reward system
Nucleus accumbens = the core of the striatum. Often called the Reward Center.
Excerpts:
The findings from these two studies thus suggest that caffeine at doses typically consumed by humans might enhance DA signaling by increasing D2/D3R levels or their affinity rather than by increasing DA release in the striatum.
However, regardless of the mechanism responsible for the increases in striatal D2/D3R availability, our results indicate that in humans, caffeine at the doses typically consumed, does not increase DA in the striatum. This is consistent with findings from microdialysis studies in rodent showing that caffeine did not increase DA in the nucleus accumbens though a study reported increases with a large but not a lower caffeine dose. Thus, on the basis of the current and prior findings and the preclinical results, caffeine at doses that are relevant to human consumption does not appear to increase DA in the nucleus accumbens
The above means that some of the feelings of arousal (not necessarily all) come from an increase in dopamine receptors, rather than dopamine itself. This occurs in the striatum, which is the central hub of the reward system.
