Millions of people now rely on antidepressants,
yet scientists still do not understand how they
work.  Two recent studies hint at an answer.  The
drugs may provide a mood lift by growing and
protecting
neurons.

Prozac and its ilk quickly alter levels of chemicals
such as serotonin in the brain, but they typically
take weeks to ease depression symptoms.  One theory
holds that the drugs work by promoting the formation
of neurons.

As a test, neuroscientist Rene Hen at Colombia
University and his colleagues treated mice with
antidepressants but killed off any newly created
neurons in the hippocampus, a brain region linked
to learning and memory

Under these conditions, the antidepressants did
not work.  Hen speculates that changes in serotonin
indirectly spur an increase in neurons in the
hippocampus.  If that is the key to fighting
depression, drugs that directly promote neuron growth
might be faster and less disruptive than existing
medications, Hen says.

Brain imaging studies also show a link between the
overall size of the hippocampus and recurrent bouts
of major depression.  Psychiatrist Yvette Sheline
at Washington University and her colleagues recently
found that patients who spent the most days depressed
without medication had the smallest hippocampi.

In this case the change may be caused by a decrease
in the connective branching between the neurons--a
decrease that could be suppressed by antidepressants.
"The more untreated depression you have, the more
it's harming your hippocampus," Sheline Says.

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Milliones de personas nunc usa antidepressantes
pro mantener sentimentos de benesser general, ma
on non sape exactemente como illos functiona.  Duo
studios recente indica un possibile causa.  Forsan
iste drogas fortifica tal sentimentos per facer
crescer e proteger neurones.

Prozac e altere simile drogas rapidemente altera
nivellos de substantias como serotonin in le cerebro,
ma typicamente un persona ha besonio de septimanas
de therapia con iste drogas ante sentir se melior.
Secundo un theoria, iste drogas functiona per promover
le formation de neurones.

Como experimento, le neuroscientista Rene Hen al
Universitate Columbia e su collegas administrava
antidepressantes a mures ma extirpava in lor
hippocampos omne neurones create durante iste therapia
(le hippocampo es un parte del cerebro que ha un
rolo in controlar processos de apprender e memorar).

Sub iste conditiones, le antipressantes non functiona.

Hen specula que cambios in le nivello de serotonin
indirectemente causa un incremento in le numero de
neurones in le hippocampo.  Si iste incremento
vermente causa un reduction de sentimentos de
depression, secundo Hen, allora drogas que
indirectemente promove le crescimento de neurones
forsan essera plus rapide e minus disruptive que le
antidepressivos de uso general currente.

Studios usante imagines del cerebro anque demonstra
un ligamine inter le grandor general del hippocampo
e grande attaccos recurrente de depression.  Le
psychiatra Yvette Sheline al Universitate Washington
e su collegas discoperiva recentemente que patientes
con periodos le plus grande de depression sin therapia
medic habeva le hippocampos le plus parve.

In tal casos, le causa de iste cambios pote esser
un reduction in le brancamento inter le neurones
del hippocampo--un diminution que pote esser
supprimite
per le uso de antidepressantes.  "Durante que un
person suffre de depression clinic sin therapia
chimic," dice Sheline, "le damno a su hippocampo
continua su augmentation."

(Per Alison McCook, publicate in "Discover", novembre,
2003, p. 12)

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