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How Antidepressants Work
Presented by
Rainsville Family Practice
Thomas L. Horton, MD
Seratonin particles
Neuron
Synapse
Receptor sites
These symbols represent neurons or nerve cells in the brain.
Thoughts and impulses are transmitted by neurons through tiny
electric currents and messages carried by chemicals called
neurotransmitters. The neurotransmitter we are discussing with
regard to depression is seratonin.
Neuron
Seratonin
Synapse
When a neuron is activated, it releases seratonins into the
synapse. These particles migrate across the synapse and
activate the receptor sites on the next neuron, thus stimulating
that neuron and relaying the impulse.
After stimulating the receptor sites, the seratonins return to the
first neuron and are reabsorbed to await the next impulse. The
second neuron releases seratonins into the next synapse, and
activates the third neuron. This process is repeated over and
over until the impulse has been transmitted to the desired
location in the brain.
Clinical depression (in contrast to simple sadness, grief, etc.)
is caused by, or exacerbated by, a deficiency of seratonins.
This may be related to genetic predisposition, chronic stress,
or illness, certain medications, or by other factors we do not
fully understand. In any event, the first neuron cannot secrete
enough messengers to activate the receptor sites adequately
on the next neuron, therefore the signal is muted. The end
result of a series of inadequate signals is the condition we
recognize as depression. Antidepressants such as the seratonin
reuptake inhibitors (SSRI’s) work to amplify the signal and
make the brain function more normally.
The seratonins are released normally and activate the receptor
sites as usual. However, instead of being reabsorbed, they are
blocked from returning to the first neuron. Think of it as
“Gortex for the brain.” The particles can get out, but they
cannot easily return. They are then free to activate more
receptor sites. This allows the existing seratonins to create a
stronger signal than would otherwise be possible.
When the first neuron fails to reabsorb the seratonins, it
begins to make new seratonin particle to replace the ones it
is missing. This process may take weeks or months to
completely restore a normal amount of seratonin. This is
the reason we recommend taking SSRI’s for six months
before stopping them. While some people seem to benefit
from continued use after six months, it is hoped that most
patients will have returned their seratonin levels to normal
and will not need the support of the medication after six
months.