Touched by Molecules

Szechuan Peppercorns, for toothaches or for fun!

Szechuan Peppercorns, for toothaches or for fun!

Eating Szechuan peppercorns has to be one of the strangest culinary experiences I’ve had. If you haven’t grabbed a few of the reddish pods, crunched them between your teeth, and let them sit on your tongue for a few minutes, go get some and do it now.

While your experience may differ, mine (and the typical experience) goes something like this. In a few seconds, your tongue numbs, then you taste pepper, then lemon, and then you experience a cool-and-hot sensation. Lastly, after maybe a minute, you feel a very strange buzzing sensation on your tongue.

“There’s a war in my mouth,” I told Diana Bautista, the UC Berkeley professor I was interviewing.

Bautista’s work is so cool. She identified the first family of touch receptors through studying the Szechuan peppercorns. Why these? Well, pain receptors were discovered through chili peppers, and then others identified through wasabi and mint and some other very wonderful plants. So spices and medicinal plants that people have noticed affect our senses and bodies are a good place to start.

Baustista’s work has many applications, like alleviating chronic pain, for example, but I would - for now - rather focus on sensation. My question - what the hell is going on that a receptor sensing heat (or cold or touch) can be triggered by a molecule that a plant makes?

A heat receptor that signals through a structural change when hot is elegant and simple, probably pretty ancient. Probably more recent are (endogenous, made by the body) molecules that can trigger the receptor to undergo the same change when it isn’t hot. Such a shortcut to tap into an already existing pathway is brilliant! Then the plants come along and make molecules that are similar enough to the endogenous molecules to trigger an unpleasant response in mammals, which don’t particularly want their mouths to feel they are burning, as protection. But humans - so often an exception - are willing to acquire the taste, for the pleasant endorphin response to the crying pain receptors.

This topic is just waiting for an artist! These are the most sensual molecules and pathways - by definition. And people do love their plant-based pain and touch receptor triggers. Capsaicin from chili peppers, menthol from mint, garlic, wasabi: there are fanatics for each of these. (And I may be an example of a fan of them all!)

Note to self - a chart to flesh out:
trpa1 receptor - wasabi (pungent isothiocyanade compounds), garlic (pungent thiosulfanates), and cannabinoids
trpm8 - mint (menthol)
trpv1 - chili peppers (capsaicin)

Links:
Diana Bautista research sumary
Nature Neuroscience paper on Szechuan peppercorns
David Julius discovered the capsaicin receptor and much more

1 Comment

  1. Olechka-persik said,

    December 9, 2008 at 5:29 pm

    Thanks for post. Nice to see such good ideas.