If you’ve ever wondered what the biochemical pathway is that gives carbonated beverages that stinging or pungent sensation as the authors of a new paper put it, wonder no more.
Ok, so probably few people other than these authors have, but I thought it was interesting enough to write about anyway.
TRPV1, the most studied nociceptor (mediates the pain response to capsaicin), and the acid-sensing ion channel (ASIC) were candidates for study, but other research suggested the “wasabi receptor” TRPA1 may mediate the sensation.
The paper is quite dense, but essentially they did some elaborate probing of trigeminal neurons (innervates the mouth) from mice and found that TRPA1 was the only receptor that is activated to mediate the sensation by the intracellular acidification by CO2.
They also noted a previous study that explained why carbonation contributes taste, because CO2 activates PKD2L1 (the sour receptor, though this is not usually represented with a sour sensation because of activation of other sensory inputs) on taste cells through extracellular generation of protons.
Because the sensations that CO2 imparts on us are now being mapped out at a molecular level, we can further explore how the various parts of the brain are influenced by it in these specific ways, as explained in the paper.
A question remains- are there any physiological consequences of frequent trigeminal TRPA1 activation from carbonated beverage consumption, considering CO2 has a relationship with lifespan (though in a different way, via olfactory detection)?
It will be interesting to see where this area goes.
Wang YY, Chang RB, & Liman ER (2010). TRPA1 Is a Component of the Nociceptive Response to CO2. The Journal of neuroscience : the official journal of the Society for Neuroscience, 30 (39), 12958-63 PMID: 20881114