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posted by Fnord666 on Tuesday April 28 2020, @07:32AM   Printer-friendly
from the count-backward-from-10...9...8... dept.

Scientists unveil how general anesthesia works: A study in mice and rat brains reveals how general anesthesia dampens high frequency brain activity by weakening synapses:

Hailed as one of the most important medical advances, the discovery of general anesthetics -- compounds which induce unconsciousness, prevent control of movement and block pain -- helped transform dangerous and traumatic operations into safe and routine surgery. But despite their importance, scientists still don't understand exactly how general anesthetics work.

Now, in a study published this week in the Journal of Neuroscience, researchers from the Okinawa Institute of Science and Technology Graduate University (OIST) and Nagoya University have revealed how a commonly used general anesthetic called isoflurane weakens the transmission of electrical signals between neurons, at junctions called synapses.

"Importantly, we found that isoflurane did not block the transmission of all electrical signals equally; the anesthetic had the strongest effect on higher frequency impulses that are required for functions such as cognition or movement, whilst it had minimal effect on low frequency impulses that control life-supporting functions, such as breathing," said Professor Tomoyuki Takahashi, who leads the Cellular and Molecular Synaptic Function (CMSF) Unit at OIST. "This explains how isoflurane is able to cause anesthesia, by preferentially blocking the high frequency signals."

[...] With further research, the researchers found that isoflurane reduced the amount of neurotransmitter released, by both lowering the probability of the vesicles being released and by reducing the maximum number of vesicles able to be released at a time.

[...] By electrically measuring the changes in the surface area of the presynaptic terminal membrane, which is increased by exocytosis and decreased by endocytosis, the scientists concluded that isoflurane only affected vesicle release by exocytosis, likely by blocking exocytic machinery.

[...] "Crucially, we found that this block only had a major effect on high frequency signals, suggesting that this block on exocytic machinery is the key to isoflurane's anesthetizing effect," said Takahashi.

[...] Overall, the series of experiments provide compelling evidence to how isoflurane weakens synapses to induce anesthesia.

"Now that we have established techniques of manipulating and deciphering presynaptic mechanisms, we are ready to apply these techniques to tougher questions, such as presynaptic mechanisms underlying symptoms of neurodegenerative diseases," said Takahashi. "That will be our next challenge."

Journal Reference:
Han-Ying Wang, Kohgaku Eguchi, Takayuki Yamashita, et al. Frequency-dependent block of excitatory neurotransmission by isoflurane via dual presynaptic mechanisms [open], Journal of Neuroscience (DOI: 10.1523/JNEUROSCI.2946-19.2020)


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  • (Score: 2) by Muad'Dave on Tuesday April 28 2020, @11:43AM

    by Muad'Dave (1413) on Tuesday April 28 2020, @11:43AM (#987785)

    Who knew isoflurane was an inductor?

    They got this part backwards, however:

    twice per second (0.2Hz) and twice every ten seconds (2Hz).

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