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Hot, hot, hot: peppers and spiders reach same pain receptor.

The burn of hot peppers and the searing sear 1  
v. seared, sear·ing, sears
1. To char, scorch, or burn the surface of with or as if with a hot instrument. See Synonyms at burn1.

 pain of a spider bite Spiders occasionally bite humans. Although 98-99% of spider bites are harmless,[1] more rarely, the symptoms of their bites can include necrotic wounds, systemic toxicity, and in some cases, death. Four genera are known to have potentially lethal bites.  may have a common cause. New research suggests that molecules in hot peppers and in a certain spider's venom target the same receptor on nerve cells.

Several years ago, scientists identified a channel on neurons that's opened by capsaicin capsaicin /cap·sa·i·cin/ (kap-sa´i-sin) an alkaloid irritating to the skin and mucous membranes, the active ingredient of capsicum; used as a topical counterirritant and analgesic.

, the molecule responsible for peppers' burn. Follow-up research showed that this channel is a member of a family of cell-surface receptors that sense both chemicals and temperature. When these channels are activated, ions flood into nerve cells and cause them to fire.

Although scientists have already studied components of spider venom that cause shock, paralysis, and death, little is known about the molecules that cause the pain. David Julius of the University of California, San Francisco Coordinates:   and his colleagues wondered whether pain-inducing venom ingredients might activate the dual-purpose cell-surface channels.

The team purchased venoms collected from a variety of spider, scorpion, and snail species known to deliver painful bites. The researchers diluted the venoms and added them to dishes containing human-kidney cells that had been genetically altered to carry various types of channels.

Only the venom of one West Indian West In·dies  

An archipelago between southeast North America and northern South America, separating the Caribbean Sea from the Atlantic Ocean and including the Greater Antilles, the Lesser Antilles, and the Bahama Islands.
 tarantula tarantula (tərăn`chələ), name applied chiefly to several species of the large, hairy spiders of the families Theraphosidae and Dipluridae of North and South America. The body of a tarantula may be as much as 3 in. (7.  species, Psalmopoeus cambridgei, sent a flood of ions into cells that sported the same receptor that's sent by capsaicin. When the scientists broke down that venom, they c identified three component molecules c responsible for the rush of ions.

To confirm that these molecules opened the capsaicin-responsive channel, the researchers added each compound separately to dishes containing nerve cells from normal mice or from mice engineered to be missing just that channel. The team found that ions entered only the cells from normal mice. Furthermore, only animals with the capsaicin-responsive channel appeared to feel pain in response to any of the molecules.

The team reports its results in the Nov. 9 Nature.

Julius notes that because triggering the receptor produces such strong pain sensations, it's not surprising that organisms as distantly related as pepper plants and tarantulas use the same defensive mechanism.

"Different organisms have figured out how to tap this site as a way of telling predators, 'You won't be comfortable if you mess with mess with

Informal, chiefly US to interfere in, or become involved with, a dangerous person, thing, or situation: he had started messing with drugs 
 me,'" he says.

Michael Caterina, who studies this family of dual-purpose cell-surface channels at Johns Hopkins University School of Medicine The Johns Hopkins University School of Medicine, located in Baltimore, Maryland, USA, is a highly regarded medical school and biomedical research institute in the United States.  in Baltimore, notes that spider venom could eventually become a powerful tool for researchers to use in investigating channels active in several types of chronic pain.

"Anything that helps us understand how these channels are activated will facilitate [development of] drugs that block these channels," he says.
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Author:Brownlee, C.
Publication:Science News
Geographic Code:1USA
Date:Nov 11, 2006
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