Depression Reversed in Mice
Donna O’Donnell Figurski
In a major advance in basic research of the brain, neuroscientists were able to reverse depression in mice by activating neurons storing a positive memory. The work was done by a team of brain scientists headed by Massachusetts Institute of Technology (MIT) Professor and Nobel Laureate, Dr. Susumu Tonegawa. This work on depression extended Dr. Tonegawa’s earlier work, on which I reported previously. The current research was done at the RIKEN-MIT Center for Neural Circuit Genetics.
The experiments were done on mice. (I have previously written why mice are good first models for humans.) Dr. Tonegawa’s team was able to use light to activate cells of the dentate gyrus, a part of the hippocampus – the area of the brain where memories are stored. They also showed that tagging a memory with a positive or negative feeling involved a pathway composed not only of neurons of the dentate gyrus, but also of neurons in two other areas of the brain: the nucleus accumbens and the basolateral amygdala.
(The use of light to activate specific neurons is a powerful and relatively recent method called “optogenetics.” The mice are genetically engineered to allow the neurons that made new memories to be turned on by light. The light is supplied by implanting optical fibers near the desired neurons, in this case in the dentate gyrus of the mouse brain, and shining light from a laser through the fibers.)
When neurons storing a positive memory were light-activated in mice that showed the symptoms of depression, the mice no longer acted depressed. The depression had been reversed by turning on those neurons. Briefly activating the neurons storing a positive memory for five days and then stopping the trigger of activation (light) was also effective in reversing depression. This shows that the positive-memory neurons do not need to be continuously activated.
Current therapeutic drugs for the treatment of depression in humans act on all neurons of the brain. It is hoped that eventually drugs will be designed for specific neurons. Another approach to stimulate specific neurons is to use a kind of “pacemaker” that could be implanted in the brain. Such treatments would have fewer side effects. (Full story)
(Clip Art compliments of Bing.)
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