Antidepressants stimulate new nerve cells

In adult monkeys, an antidepressant therapy has induced new nerve cell growth in the hippocampus, a brain area responsible for learning and memory. A similar process may occur in humans, the research suggests, and may help explain the effectiveness of antidepressant therapys.

The results, the first from nonhuman primates, are similar to those previously seen in rodents. They suggest that creation of new nerve cells, a process known as neurogenesis, is an important part of antidepressant treatment. Researcher Tarique Perera, MD, at Columbia University, and his colleagues observed changes in the number of brain cells in the dentate gyrus region of the hippocampus. The study is reported in the May 2 issue of The Journal of Neuroscience
The growth of new nerve cells in the hippocampus has been suggested as the way antidepressants work in rodents, says Eric Nestler, MD, PhD, of the University of Texas Southwestern Medical Center. "However, the clinical relevance of this action has remained controversial, in part, because of uncertainty as to whether similar neurogenesis occurs in humans," he says. "This finding further supports the potential clinical relevance of changes in neurogenesis seen in rodent models."

Perera and the team treated a group of monkeys with electroconvulsive shock (ECS), an animal version of the highly effective clinical antidepressant electroconvulsive treatment. They saw an increase in new nerve cells in the hippocampus. Over four weeks, a majority of these cells became mature neurons.

These brain changes were not a response to tissue damage, Perera says, because no evidence of increased cell death was found in the ECS treated animals. In fact, the scientists observed that the ECS therapys increased production of a protein (BCL2) that protects neurons from damage.

"These findings support the hypothesis that induction of neurogenesis is a necessary component in the mechanism of action of antidepressant therapys," Perera says.


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