Now scientists have found hints of how ketamine works in the brain.
In mice, this drug quickly improves the functioning of certain brain chains involved in the mood, reports the international team in the journal . Then, after a few hours, she begins to repair faulty contacts between the cells in these chains. An anesthetic variant of ketamine is already used to treat thousands of people with depression. But scientists are relatively little aware of how ketamine and similar drugs affect brain chains.
The study offers a "significant breakthrough" in the understanding of scientists, says Anna Beehler, a neurophysiologist from INSERM, the French equivalent of the National Institutes of Public Health in the United States who did not participate in the study. But there are still many other issues, ̵
. The new study seems to add important details about how and when these new synapses affect brain chains, says Ronald Duman, a professor of psychiatry and neurology at Yale University. Study of antidepressant effects of ketamine in mice was a problem. "There's probably no such thing as depression in the mouse," says Dr. Conor Lister, a neurophysiologist and psychiatrist at Weill Cornell Medicine in New York and author of the article Science . Spray for Severe Depression “/>
So Liston and a group of scientists from the United States and Japan gave mice a stress hormone that made them act depression. For example, animals lost interest in their favorite activities, such as drinking sugar and studying the labyrinth.
Then the team used a special laser microscope to study the animal's brain. Researchers were looking for changes in synapses.
"Stress is associated with loss of synapses in this region of the brain, which we believe is important in depression," says Liston. And, of course, in mice suffering from stress, many synapses have been lost. Further scientists gave the animals a dose of ketamine. And Liston says that then they noticed something weird.
"Ketamine actually restores many of the same synapses in the same configuration that existed before the animal was subjected to chronic stress"
This conclusion has shown that ketamine can alleviate depression in humans. But this does not explain how ketamine can work so fast.
Was this drug really a creation of these new synapses in just a couple of hours?
To use, the team used technology that makes living brain cells light fixtures. under a microscope.
"You can imagine Van Gogh's Starry Night, ," says Liston. "The cells of the brain are ignited when they become active and become dimmer when they become inactive."
This allowed the team to identify the brain chains by looking for groups of brain cells that were lit together.
After the mice received the ketamine, it took less than six hours, when the brain chains that were stressed began to work better. Mice also ceased to act depressed during this period of time.
But both of these changes took place long before the drug was able to recover many synapses.
up to 12 hours after treatment with ketamine, we have really seen a great increase in the formation of new neuronal relationships, says Liston.
The study showed that ketamine causes a two-stage process that relieves depression. Firstly, the drug somehow reconciles the broken brain chains to temporarily work better. It then provides long-term fixation by restoring synaptic relationships between the cells in the chain.
One possibility is that the synapses are restored spontaneously after the cells in the chain begin to shoot in sync, says Beyler, who wrote a comment to the study.
A new study suggests not only how ketamine works, but also why its effects tend to wear out in a few days or weeks, she says.
"We can imagine that ketamine always has this short-term anti-depressant effect, but then, if synaptic changes are not supported, you will have a relapse," says Beyeler
If this is true, – she says, – the next task of scientists is to find a way to save brain chains that have recovered ketamine. 19659034]