Neurotransmitters are specialized chemical messengers
that send a message from one nerve cell to another.
Each neurotransmitter plays a different role in the body.
However certain man made chemicals can replace or block these chemical messengers.
The chemicals are either called agonists, or antagonists. Agonists mimic the desired neurotransmitter allowing it to be read
as such. The most common form is the drug morphine, a pain killer, taking the place of endorphins, the body's natural anesthetic.
Antagonists do the opposite, the do not allow neurotransmitters to be read at all.
A Few Types of Neurotransmitters