What is a Neurotransmitter
A neurotransmitter is one of a class of chemical substances that carry messages between neurons. Typically, a sending neuron releases small amounts of a neurotransmitter, and this activates receptors on the receiving neuron.
Receptor activation then initiates a series of chemical changes in the receiving neuron, and if enough receptors are activated, the receiving neuron may itself become active and send the message along.
A variety of neurotransmitters have been identified, including acetylcholine, dopamine, serotonin, and norepinephrine. Typically, neuronal receptors are specialized to only respond to one type of neurotransmitter. This allows for a high degree of specialization in how messages are transmitted between neurons: one neuron may respond strongly to release of a particular neurotransmitter while its neighbor may be relatively insensitive.
Neurotransmitter imbalances have been implicated in several diseases such as Alzheimer's disease and Parkinson's disease, and in a variety of psychiatric illnesses such as schizophrenia and depression. Many drugs work by altering the level of specific neurotransmitters in the brain (see, e.g., cholinesterase inhibitors).
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain - Artwork copyright © 2000 Catherine E. Myers