研究发现抗抑郁剂作用机理

http://www.100md.com 2000年12月18日

     NEW YORK (Reuters Health) -- New research may help explain, at least in part, how antidepressant medications work.

    In a study conducted in rats, regular use of antidepressants promoted the growth of new cells in the hippocampus, an area of the brain where cells are known to waste away in people who are depressed. The hippocampus plays a role in learning, memory and mood.

    Several types of medications have been shown to treat symptoms of depression, but exactly how these drugs work remains a mystery, according to the lead author of the new study, Dr. Ronald S. Duman, of Yale University in New Haven, Connecticut.

    In an interview with Reuters Health, Duman cautioned that it is too early to know whether the growth of new brain cells is the primary line of action of antidepressants. However, he said, ``This is one part of the story.''

    Previous research has shown that depression and stress--physical and psychological--can destroy neurons and prevent new cells from growing in the hippocampus. Duman's team gave the antidepressants tranylcypromine, fluoxetine and reboxetine to rats. Each drug represents a different class of antidepressant medication.

    The researchers also treated rats with electroconvulsive seizure therapy and an antipsychotic drug.

    In rats treated with an antidepressant for 2 to 4 weeks, the number of brain cells in the hippocampus increased 20% to 40%, the authors report in the December 15th issue of The Journal of Neuroscience. After 2 to 4 weeks of electroconvulsive seizure therapy, the most effective therapy for hard-to-treat depression, the number of neurons increased by about 50%.

    But it takes a while for the benefits of antidepressants on brain cell growth to begin, the report indicates. Neuron numbers did not increase in rats that were treated with an antidepressant for 1 to 5 days. The antipsychotic drug did not have any effect on neurons in the hippocampus.

    Although antidepressant drugs may provide other benefits besides encouraging the growth of neurons in the hippocampus, Duman and colleagues plan to look closer at this process.

    ``We are focusing on how antidepressants do this,'' Duman said. If scientists can understand how the drugs promote cell growth, they may be able to develop new drugs that do an even better job, he explained.

    SOURCE: The Journal of Neuroscience 2000;20.

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