Since this story is written for the layman they use the term "cell birth". But what is really happening is that adult stem cells in the hippocampus divide. One cell remains an adult stem cell and stays in the hippocampus. The other travels up into the brain and converts itself into a nerve cell. Well, this process is probably happening in order to form new memories, possibly new reflexes, and to replace damaged cells that die. Suppression of this process may either cause depression or possibly it doesn't cause the initial depression but does prolong it. Anti-depressants are known to stimulate hippocampal adult stem cells to divide and so the thinking is that this stimulation may be one of the ways that anti-depressant drugs relieve depression. There are now many scientists pursuing this line of thought and looking for drugs that will more quickly stimulate hippocampal adult stem cells to divide.
Stress, which plays a key role in triggering depression, suppresses neurogenesis in the hippocampus.
Antidepressants, on the other hand, encourage the birth of new brain cells.
Animals must take antidepressants for two or three weeks before they bump up the birth rate of brain cells, and the cells take another two weeks to start functioning. That's consistent with the lag time antidepressants show before they lift moods in people.
If an antidepressant is given during a period of chronic stress, it prevents the decline in neurogenesis that normally occurs.
You can also fiind the previous article here.
In a related report stress hampers learning ability in female rats but Prozac prevents stress's effects:
Shors and her research team, Benedetta Leuner, Jacqueline Falduto and Sabrina Mendolia, studied adult female rats treated with the antidepressant Prozac and a control group that received no treatment. They found that after a stressful event, learning was impaired in the control group but not in the group treated with Prozac. The researchers also found that only chronic treatment with Prozac was effective, which is consistent with reported efficacy of Prozac in patients with depression and other mental disorders.
"Importantly," Shors pointed out, "unstressed females treated with Prozac did not differ from unstressed, untreated females, indicating that Prozac itself did not affect learning."
Shors noted that males and females differ in their responses to stressful experiences. The researchers have found that exposure to a stressful experience that impairs new learning in females actually enhances new learning in males.
These results also suggest a reason why depression is more common in old folks: their adult stem cells are also aged and very likely not as able to divide and differentiate into nerve cells. In order to rejuvenate people and make their bodies young again it will be essential to rejuvenate the adult stem cells in various adult stem cell reservoirs throughout the body. If hippocampal adult stem cells could be rejuvenated it might be possible to reduce the incidence of depression, improve memory, and even to raise intelligence. Since the demand for more effective anti-depressant treatments is so large this theory about hippocampal adult stem cells having a role in prolonging depression may cause depression researchers to develop methods to rejuvenate hippocampal adult stem cells. Hence attempts to develop more advanced anti-depressant treatments may contribute to the development of anti-aging therapies.
|Share |||Randall Parker, 2002 October 30 04:45 PM Brain Emotions|