From a
Sept. 12 article in the Guardian, it appears that zolpidem, branded as Ambien in the US and Stilnox in South Africa, when administered to people in a coma or a persistent vegetative state, can restore alertness, awareness, and the ability to communicate.
No one yet knows exactly how a sleeping pill could wake up the seemingly dead brain cells, but Nel and Clauss have a hypothesis. After the brain has suffered severe trauma, a chemical known as Gaba (gamma amino butyric acid) closes down brain functions in order to conserve energy and help cells survive. However, in such a long-term dormant state, the receptors in the brain cells that respond to Gaba become hypersensitive, and as Gaba is a depressant, it causes a persistent vegetative state.
It is thought that during this process the receptors are in some way changed or deformed so that they respond to zolpidem differently from normal receptors, thus breaking the hold of Gaba. This could mean that instead of sending patients to sleep as usual, it makes dormant areas of the brain function again and some comatose patients wake up.
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"The results so far could be potentially very important," says Meyer. "We have never before spoken of damaged cells in the brain going into hibernation -- we have thought of them as necrotic, or dead, cells. But we know cells can go into hibernation in the heart and thyroid, so why not the brain? If there are hibernating cells in damaged brains, it may be that this drug helps to wake them in some people."