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Especially when drinking water after the fact, mint can give a sharp cold sensation inside one's mouth. What process causes the sensation to occur?

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Menthol it self gives a cold feeling in the mouth because it is active at the same receptor (an ion channel) on the tongue that cold temperature triggers. Interestingly, although they act at the same receptor, they act at different sites, so that provides the intensified response when eating a mint and then drinking water. This reference gives an excellent detailed answer, with references to the original papers, which I'll summarize here.

Menthol acts at the TRPM8 protein which forms an ion channel that allows $\ce{Na+}$ and $\ce{Ca^2+}$ ions to flow into cells and this sends a signal saying "cool" to the brain. (As an aside, this protein monitors temperature across the body and not just on the tongue.) Cold temperatures actually change the confirmation of this protein, which allows the ions to flow more freely, and sends the signal to the brain. Menthol, on the other hand, stabilizes the open channel (allowing ions to flow even more freely) and also...

“menthol shifts the voltage dependence of channel activation to more negative values by slowing channel deactivation”. This is very significant to my question because it supports a claim made by the first web page I visited which stated that menthol acts on the receptors, leaving them sensitized for when the second stimulus is applied (i.e. cold water) resulting in the enhanced sensation. This mechanism of binding is very clearly different from the mechanism of cold affecting the TRP channels. This is why the sensation is increased when both stimuli are applied, yet is not affected after addition stimulation from the same stimuli (i.e. eating another mint).

All in all, pretty cool.

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  • $\begingroup$ "conformation" (typo). A great answer. $\endgroup$ – CowperKettle Jun 22 '16 at 5:09
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    $\begingroup$ Where's this citation from? $\endgroup$ – Mithoron Sep 7 '17 at 12:11
  • $\begingroup$ @Mithoron I don't think you are going to get an answer. It looks as though Janice hasn't been on the site since 2012. $\endgroup$ – Tyberius Sep 7 '17 at 14:09
  • $\begingroup$ @Tyberius Just felt it should be pointed out. It is probably traceable so maybe someone (or even myself) will check it. $\endgroup$ – Mithoron Sep 7 '17 at 15:05

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