How do chemicals in brain like dopamine affect the behaviour, lack of which cause behavioural problems, is there a test to check the levels and cure?

Great Question: There are three major Dopamine pathways in the brain that help regulate emotions, blood pressure, movements, etc. When overactive can cause psychotic disorders, ; ocd etc. When underactive can cause symptoms of parkinsons. Most disorders of Dopamine are treated based on symptomatology. Either replace or suppress domanine activity. I am not aware of a generalized test commonly given to ck dopamine.