plants and peripheral nervous system receptors

You might wonder what plants have to do with peripheral nervous system receptors. It does seem a little odd to associate the two. However there's an article in yesterday's issue of Nature (May 30, 2007) regarding the menthol receptor TRPM8 and how it senses cold. In so doing, the receptor illuminates a mechanism that mediates how the body experiences strong stimuli like temperature that can cause pain.

As such, the receptor -- known as menthol receptor TRPM8 -- provides a target for studying acute and chronic pain, as can result from inflammatory or nerve injury, the researchers say, and a potential new target for treating pain. The senior author on this paper is David Julius, chairman and professor of physiology at UCSF. In 2002, his lab discovered that the TRPM8 receptor was activated by chemical cooling agents such as menthol, a natural product of mint, and cool air.

According to Dr Julius, "It's been known for years that menthol and related cooling agents evoke the psychophysical sensation of cold -- somehow by interacting with the aspect of the sensory nervous system that's related to cold detection."

The finding is the latest of a series of discoveries led by the Julius Lab on the molecular mechanisms of temperature sensation and pain. In 1997, the lab cloned the gene for the capsaicin receptor, the main pungent ingredient in some chili peppers (Nature, Oct. 23, 1997), and in 2000 reported that, in mice, the receptor triggers the nerves to fire pain signals when they are exposed to high ambient heat or the fiery properties of peppery food. (Science, April 14, 2000). The study demonstrated that capsaicin and noxious heat elicit the sensation of burning pain through activation of the same receptor on sensory neurons.

Why, you might ask, am I bothering to talk about all this? The obvious application for research like this is to offer potential targets for developing analgesic drugs that act in the peripheral nervous system, rather than centrally, where opiate receptors act. But what I want you to think about is the plant oriented implications of this research.

It's easy to understand why our nerves would interpret cold as being well, cold. And likewise warmth as being warm. But why would our nerves interpret hot peppers as being hot? Or menthol as being cold? What percentage is there in our bodies interpreting plant chemicals as being temperature related?

I don't know the answer to that but I suspect I've got the question there backwards. I'd assume that natural selection has given some plants protection from animal consumption in this fashion. A chemical like capsaicin makes animals avoid the plant that makes the capasaicin by convincing the animal that their mouth parts are being burned. Since animals that don't avoid burning sensations don't survive long, this turns out to be an excellent survival strategy for the pepper plant. Too bad they didn't see Mexican Restaurants, chili con carne, and BBQ contests coming in the future...


kenju said…
Does that have anything to do with bugs that taste bad because they are poison? Or bugs/worms/toads that have harsh color markings because they are poison? Don't know why I thought of that.
SassyAssy said…
What Sassy read: "Plants...blah blah blah...Mexican Restaurants" hmmm that gives me an idea about what I will be doing Sunday!!! *grin*
Anonymous said…
sassy must be that Chipolte girl
I didn't really understand a word of this Dave...except PAIN, COLD, and PLANTS....But if you discover what I can do about chronic back pain, I will be grateful, forever!

BTW: I have a new post up that has a "decades old photograph" of me...LOL! But it is interesting....!

Michele sent over here this early A.M., my dear.
Mr. Althouse said…
This is all very intriguing, Dave. Especially about how some plants evolved the survival techniques they did. And the implications as far as medicine is concerned are far reaching indeed. I read somewhere that something like 70 percent of all medicines can be traced back to plant origins.

Michele sent me,

It's all greek to me, except Mexican Restaurants..and now I'm hungry for a burrito and it's only 7:30 in the morning. That's bad.

Oh hello, from Michele's :)
PI said…
If you are trying to blind me with science you are succeeding. I like to take things on trust viz nettles sting, dock leaves sooth, sugar is sweet and not worry about the reason why but then I used to be blonde.
Michele says hi!
Paul said…
Here from Michele's this nice Saturday morning.

I'm glad OOLH said what she said, cuz I feel a little shy about saying the same thing. You have such a great blog, but sometimes is just goes way over my head.

I will tell you I'm on a special sweet see food diet. No pain there!
Becky68 said…
Thanks for stopping by my blog last night, that is interesting stuff, I read in a gardening book that pouring chilli powder around the perimeter of my garden can help to keep deer away because they don't like the smell, I haven't tried it because you have to reapply after rain & we're having thunderstorms almost every afternoon lately.
Don't begrudge the storms, they're heavy, but pass quickly & don't always drop much rain, yesterday's was the best all week & we had about a half inch in my rain gauge after all was said & done.

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