Dopamine is a neurotransmitter, a chemical that carries a signal across nerve junctions. You might know of it because of its links to Parkinson's disease, but it's actually pretty widespread in the brain and does a number of interesting things.
Researchers from the University of Bristol have discovered that a chemical compound in the brain can weaken the synaptic connections between neurons in a region of the brain important for the formation of long-term memories.
The nervous system is a network of specialized tissues that regulates thoughts, emotions, actions, sensations, and basic body functions. The brain on the other hand is the body's control center. The brain sends messages to and receives stimulation from all parts of the body.