Not only can dopamine levels be an issue, but also dopamine sensitivity. Often times there can be a dopamine hypo-sensitivity, so I've written an article on how to increase dopamine receptors.
Dopamine receptors: 14 Best supplements and practices and to increase it » MenElite
What is Forskolin? It was mentioned in an old thread:
It seems to have some positive effects, according to some parts of the wikipedia page:
Apparently some people supplement with it, though they advise to be extremely careful to avoid a stroke.