Depression Drugs — SSRIs — May Reorganize Brain Plasticity, New Research Suggests

ScienceDaily (Mar. 18, 2011) — Selective
serotonin reuptake inhibitors (SSRI) such as Prozac are regularly used to treat
severe anxiety and depression. They work by immediately increasing the amount of
serotonin in the brain and by causing long term changes in brain function.
However it can take weeks of treatment before a patient feels any effect and
both beneficial effects and side effects can persist after treatment is

New research published by BioMed Central’s open access journal Molecular
investigates physiological changes within the brain that may be
caused by SSRI treatment.

The hippocampus is an area of the brain involved in long term memory and
spatial awareness, and is involved in symptoms afflicting people with
Alzheimer’s disease, such as loss of memory and disorientation. Neuronal cells
in the hippocampus can change their activity and strength of connections
throughout life, a process known as plasticity, which thought to be one of the
ways new memories are formed. Altered plasticity is often associated with
depression and stress.

Researchers from the Department of Pharmacology, Nippon Medical School,
showed that chronic treatment of adult mice with fluoxetine (Prozac) caused
changes to granule cells, one of the main types of neuronal cells inside the
hippocampus, and to their connections with other neuronal cells. The granule
cells appeared to undergo serotonin-dependent ‘dematuration’, which increased
their activity and reversed adult-type plasticity into an immature state. These
changes to the cell’s plasticity were associated with increased anxiety and in
alternating between periods of hyper or hypo activity.

Katsunori Kobayashi explained, “Some of the side effects associated with
Prozac in humans, such as anxiety and behavioral switching patterns, may be due
to excessive dematuration of granule cells in the hippocampus.”

BioMed Central (2011, March 18). Depression drugs — SSRIs — may reorganize
brain plasticity, new research suggests. ScienceDaily. Retrieved June
6, 2011, from­/releases/2011/03/110316084425.htm