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 Research & Giving News Article  New Neuron Growth in Monkeys The results, the first from nonhuman primates, are similar to those previously seen in rodents in that they suggest that creation of new nerve cells, a process known as neurogenesis, is an important part of antidepressant therapy. The study, reported in the May 2 issue of the Journal of Neuroscience, was led by Tarique Perera, M.D., of Columbia University’s College of Physicians and Surgeons, and a recipient of a NARSAD Young Investigator award in 2004. Dr. Perera and colleagues observed changes in the number of brain cells in a region of the hippocampus called the dentate gyrus. The appearance of new nerve cells had been suggested as the way antidepressants work in rodents, according to Eric Nestler, M.D., Ph.D., chairman of the University of Texas Southwestern’s Department of Psychiatry and a member of NARSAD’s Scientific Council. However, “the clinical relevance of this action has remained controversial, in part, because of uncertainty as to whether similar neurogenesis occurs in humans.” In Dr. Nestler’s view, Dr. Perera’s study “further supports the potential clinical relevance of changes in neurogenesis seen in rodent models.” Dr. Perera and the research team treated a group of monkeys with electroconvulsive shock (ECS), an animal version of the highly effective clinical antidepressant electroconvulsive therapy. 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, Dr. Perera said, because no evidence of increased cell death was found in the animals treated with ECS. In fact, the researchers found that the ECS treatments increased production of a protein called BCL2 that protects neurons from damage. In depressed people, the volume of the hippocampus has been observed to be smaller than that of people who are not depressed. Moreover, various impairments consistent with hippocampal malfunction, such as memory defects and increased stress hormone levels, are also seen in certain depressed patients. These alterations are thought to be the result of suppressed hippocampal neurogenesis. Interventions that ameliorate depression, including all classes of antidepressants, mood-stabilizers, and environmental enrichment, are thought to stimulate neurogenesis. Yet the link between neurogenesis and antidepressants is circumstantial and prior to the present study had never been demonstrated in monkeys. “These findings support the hypothesis that induction of neurogenesis is a necessary component in the mechanism of action of antidepressant treatments,” said Dr. Perera. Co-authors of the study include Sarah H. Lisanby, M.D., of the New York State Psychiatric Institute (NYSPI) and Columbia, a 2003 NARSAD Independent Investigator; Luca Santarelli, M.D., of NYSPI, a NARSAD 2000 and 2002 Young Investigator; Rene Hen, Ph.D., of NYSPI, a NARSAD 2003 Distinguished Investigator; and Harold A. Sackeim, Ph.D., of Columbia, a NARSAD 2006 Distinguished Investigator. In addition to NARSAD, the study was supported by the National Institute of Mental Health at the National Institutes of Health and the American Psychiatric Association Lilly Research Fellowship Award. This article was adapted in part with permission from the Society for Neuroscience. |
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