is a neurotransmitter,
a chemical used to carry messages between neurons.
Although only about 1% of the body's serotonin is localized
in the brain, serotonin has profound effects on brain function.
(The remaining 99% helps carry messages elsewhere in the body,
such as the spinal cord and muscles.)
Serotonin's effects are complex and incompletely
understood. Too little serotonin may be a cause of depression,
and drugs that increase brain levels of serotonin (the serotonin-specific
reuptake inhibitors, or SSRIs) can alleviate depression
-- but they may also cause side
effects such as insomnia, anxiety and loss of libido.
Several diet drugs, including flenfluramine
(withdrawn from the US market in 1977) and sibutramine (brand
name Meridia) increase brain levels of serotonin, increasing
feelings of satiety and decreasing the desire to eat.
Various psychedelic drugs, including LSD,
resemble serotonin chemically, and may work by mimicking some
of the effects of serotonin in the brain.
by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain