The Science of Dopamine
As we previously explained, dopamine is one of more than 100 chemicals known as neurotransmitters, which enable neurons in the brain to communicate with one another and manage everything that happens in our body [source: Purves et al.].
Like all neurotransmitters, dopamine goes through a cycle, which begins with it being synthesized by a neuron (called the presynaptic cell). That cell releases the dopamine and it floats out into the synapse, the gap between neurons, and then makes contact and binds with structures called receptors on the other neuron, which then transmit the signal to the second neuron. After the dopamine accomplishes its mission, it's rapidly removed and degrades. The effects of dopamine on your brain depend a lot on which neurons are involved and which receptors are binding the dopamine [sources: Brookshire, Purves et al.].
As molecules go, dopamine is fairly compact, consisting of just 22 atoms. Only a tiny portion of the brain's 100 billion or so neurons — as few as 20,000 — generate dopamine, most of them in midbrain structures such as the substantia nigra, which helps control movement, and the prefrontal cortex [sources: Angier, Deans].
Those specialized neurons make dopamine by taking an amino aside called tyrosine and combining it with an enzyme, tyrosine hydroxylase. Add another step to the chemical reaction and you would get a different neurotransmitter, norepinephrine [source: Deans].
In terms of evolutionary history, dopamine has been around for a long time, and it's found in animals from lizards to humans. But people have a lot of dopamine and over time, we seem to have evolved to produce more and more of it, possibly because it helps enable us to be aggressive and competitive. As evolutionary psychiatrist Emily Deans wrote in 2011, "dopamine is what made humans so successful." Researchers have found that humans have about three times as many dopamine-producing neurons as other primates [source: Parkin].