dopamine

We are all addicted to "dopamine." Dopamine is a drug produced by our body which makes us "feel good." We buy things because the "buying" (more than the "owning") gives us a dopamine rush. That's why we never get enough stuff. It's like an orgasm. No matter how many orgasms we have, we want to have at least one more.

"Dopamine belongs to a group of brain chemicals called monoamines, a family of neurotransmitters involved in many different aspects of behavior -- personality, depression, drug and alcohol use, aggression, eating, and sex. It is tyrosine, a common amino acid found in many foodstuffs, with a few little changes at one end. Dopamine alone is not enough to give us a rush. Dopamine is a key that opens a lock. The lock is called a receptor, a large protein that sits on the surface of brain cells. The receptor is recognized by dopamine but by no other chemical, just like a lock can only be opened by the correct key. When the dopamine snuggles into the waiting receptor, the tumblers turn. Inside the brain begins a series of chemical reactions."

[pp. 35-36, LIVING WITH OUR GENES: Why They Matter More Than You Think, by Dean H. Hamer & Peter Copleland; Anchor, 1999]