Researchers have shown that increased levels of dopamine increase impulsiveness and the desire for instant gratification. At the same time, the amygdala, involved in emotions, lit up.
It seems much of life is a conflict between seratonin and dopamine. One wants quiet, and the other wants loud music. One wants rest, and the other wants activity, especially something new. One puts money away in a tax-deferred annuity, and the other takes off to Jamaica for the weekend.
The test was done by giving people L-Dopa, which increases dopamine levels. They also tried using a dopamine suppressor, but it didn't have the effect of reducing impulsiveness.