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Comment by lpribis | Hacker News Reader

No, xenon is a NMDA antagonist meaning it has dissociative/anaesthetic effects like ketamine or nitrous oxide.

TFA talks about the effects coming on "within seconds" of inhalation, so it is clearly not just hypoxia which takes tens of seconds or minutes to manifest.

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Asphyxiation with inert gases causes hypoxia very quickly. It's not like holding your breath. Lungs don't actively pump oxygen; gases just diffuse along their partial pressure gradients. Air has higher partial pressure of oxygen than blood does, so the oxygen diffuses from the air to the blood. If you fill the lungs with inert gas the oxygen diffuses back out again. You're effectively breathing in reverse.

Filling the lungs with vacuum has the same effect. You have about 5 to 10 seconds before you're incapacitated:

https://en.wikipedia.org/wiki/Time_of_useful_consciousness

Either way, it has been known for a while that xenon is an NMDA antagonist (hypoxia aside).

And, importantly, it's always mixed with oxygen when used that way.

How does it do that without forming chemical compounds? Is it like a catalyst for another reaction or something?

Even though xenon doesn't easily form "compounds" in the normal chemical sense, it does weakly interact with other molecules through van der Waals forces, which are strong enough to affect the functioning of various receptors in neurons.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6467505/

I'm not an expert on the biochemistry, but Wikipedia has a summary of some of the known interactions at:

https://en.wikipedia.org/wiki/Xenon#Anesthesia

It will still react through (weaker) non covalent forces, like van der Waals force.

Reactions don't need to happen, the magnesium ion is a single atom that interacts with the NMDA receptor to block it at specific potentials. When the postsynaptic neuron gets enough input at a synapse, there is enough change in the charge inside the cell where it allows the Mg2+ ion to be displaced from the pore to allow cations to pass through

Our cells use single atoms, usually in the form of charged ions, on a regular basis and we would not survive without them

But wouldn't xenon (as a noble gas) be pretty hard to ionize? Without a charge it shouldn't interact the way ions do.

Charge is not the only way that molecules interact

https://en.m.wikipedia.org/wiki/Van_der_Waals_force

I'm not very knowledgeable on this, but my understanding is that xenon can dissolve in the lipids in the brain and influence reactions in that state. This paper [1] seems to show that xenon can displace glycene in the NMDA receptors. The receptor is a "door" and glycene is one of the "keys" to open. By binding or interacting with the glycene site on the receptor, xenon keeps glycene from reaching the receptor, inhibiting it.

[1] https://pubs.asahq.org/anesthesiology/article/112/3/614/1084...

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