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 |
