There are probably over a hundred compounds in cacao that might possibly have effects on humans. I don't want to speculate on the ones that are not known. One that is known is theobromine.
I have seen a claim that cacao does not actually have caffeine, but I haven't checked it. Cacao might not have theophylline either. The link did not work for me.
no caffeine in cacao
Here is a picture of the structure of adenosine.
Here is a picture of the structure of theobromine.
Theobromine is kind of similar to a part of adenosine. Adenosine causes your heartbeat to slow etc. There are four known receptors for adenosine which cause different cells to do different things. It's complicated.
what adenosine does
So it's plausible that theobromine might interfere with adenosine attaching to those receptors, and might cause the result you'd get with less adenosine in your bloodstream.
Salsolinol is kind of similar to dopamine. It is created in the human brain and some gets excreted. It might possibly have some use itself and not be a waste product of something that matters. Here's one link from 2006 speculating about that.
The link I gave which appears to show serotonin up to 5% by weight is probably extremely misleading. Other sources have that in micrograms per gram. Serotonin in food is emetic -- you shit it out fast. Likely serotonin in cacao doesn't give you a lot of serotonin in your bloodstream. But it could be worth a better lit search.