TUESDAY, Dec. 27, 2005 (HealthDay News) -- Selective serotonin reuptake inhibitors (SSRIs), a widely used class of antidepressant drugs that include Celexa, Paxil, Prozac and Zoloft, boost nerve fiber growth in key parts of the brain, according to a study with rats.
The finding may help explain how SSRIs work and why it takes a few weeks before some antidepressants begin to have an effect.
The research team from Johns Hopkins University found that SSRIs increased the density of nerve impulse-carrying axons in the frontal and parietal lobes of the neocortex and part of the limbic brain that controls smell, emotions, motivations, and organs that work reflexively, such as the heart, stomach and intestines.
"It appears that SSRI antidepressants rewire areas of the brain that are important for thinking and feeling, as well as operating the autonomic nervous system," study leader and neuropathologist Dr. Vassilis E. Koliatsos said in a prepared statement.
It has long been thought that antidepressants work by increasing synaptic concentrations of the brain chemicals serotonin and norepinephrine, enhancing or stimulating their transference.
"But our findings -- that serotonin reuptake modulators increase the density of nerve synapses, especially in the front part of the brain -- may offer a better explanation of why antidepressants are effective and why they take time to work," Koliatsos said.
The study appears in the January issue of the Journal of Neurochemistry.
The American Academy of Family Physicians has more about antidepressants.