Question

How does the extra dopamine released during drug use affect the brain?

Answer 1

The answer is:

It can lead to intense cravings for the drug when it is not available.

Answer 2

Dopamine is a neurotransmitter that is related to the positive feedback/reward system of mammal brains. Higher amounts of dopamine released in response to any stimulation will result in a stronger desire to recreate that stimulus. One could say that the extra dopamine released during drug use causes the brain to desire using the drug again to receive that same pleasurable reward sensation.