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I make a killer potion: deadly frogs, toxic snails, and poisonous puffer fish could fill, up your future medicine cabinet. Turn the page to find out how ...

Peering through the overgrown South American rainforest, Taran Grant spies a splash of yellow. It appears to be a poisonous frog. The biologist nabs the critter before it springs away. Then, he licks the milky slime oozing from the frog's back. Is this a scene from TV's Fear Factor? Nope. Grant is on a mission: This taste test will tell him if the frog is a true threat or a false foe. "We don't recommend this, but scientists can find out if a frog is poisonous by touching the tip of their tongues to the backs of frogs," explains Grant. co-curator of the Frogs exhibition at New York's American Museum of Natural History. "The effect ranges from a nasty taste to a slight constriction (narrowing) of the throat." Even worse, if scientists lick the wrong frog, they could die.

Why take the risk? One reason is the ongoing hunt for future medicines. Over time, some species of frogs, fish, snails, and other animals have developed deadly toxins to fend off enemies. Now, some of these animal toxins are leading to new painkillers, explains Grant.

Example: Poison dart frogs ooze a bitter-tasting toxin from their skin. When an unsuspecting predator tries to eat the frog, the hopper's toxin paralyzes (causes the loss of movement in some parts of the body) nerves that control the enemy's breathing and blood pumping.

"The amount of poison in the two-inch golden dart poison frog, or Phyllobates terribilis (FY-low-bates ter-EE-blis), is enough to kill about 10 adult humans." explains Grant. But scientists have found that in very small amounts, the frog's toxins merely numb their targets. By carefully harnessing these body-numbing chemicals. scientists have begun to make drugs that can ease debilitating pain that some people feel.

THAT HURTS!

Stubbing your toe can send you howling in pain. But the shooting sensation soon fades away. Imagine having agonizing aches for months or years with no obvious injury. "One out of three people [in the U.S.] suffers from chronic pain [such as fibromyalgia, a condition that causes whole-body muscle pain]," says Penney Cowan, founder of the American Chronic Pain Association. That's about 50 million people--including teens. "They have to manage the pain so it doesn't control their lives." she says. But in many cases, the root of the pain is a mystery.

"You perceive pain in your brain, no matter where it originates," says Toto Olivera. a biologist at the University of Utah. Whether you burn your finger or have a serious accident, your nervous system (body system that includes the brain, spinal cord, and nerves) kicks into high gear. A series of neurons (nerve cells) carries electrical signals up the spinal cord to the areas of the brain that recognize these impulses as pain (see Nuts & Bolts. p. 17). Chronic pain forms when faulty neurons transmit pain messages even after an injury has healed.

Blocking these impulses before they reach the brain kills the pain. says Olivera. "Right now. the best drug [for chronic pain sufferers] that does that is morphine (MORE-feen)" he says. Morphine molecules (particles of two or more atoms, or the smallest unit of an element, joined together) mimic the body's own anti-pain agents. These endorphins stop pain messages in their tracks. "The problem with morphine," says Olivera. "is that patients build up a tolerance--after a while [a certain dose] doesn't work." So doctors have to give patients more medicine. That's why scientists are searching the planet, including the oceans, for new chemicals that could control chronic pain.

BLOCK THE PAIN

Beachcombers beware. Tiny cone snarls of the genus (classification of organisms) Conus (CONE-us) may look innocent, but they can strike lightning-fast with a deadly sting. That prompted researchers to ask: How do the snails harpoon their victims? Turns out, says Olivera, "They inject a cocktail of toxins. One animal can produce about 50 different [poisons]."

Mixed together, the toxins deliver a one-two punch. First, the concoction zaps a victim with an electric shock, stunning it. Then, it blocks the enemy's nerve communication with the muscles. The result: paralysis.

But isolate the chemical ziconotide (zih-KAH-noh-tide) from this mix, and the toxin merely disables pain signals in humans. How? Nerves need the element calcium to channel pain messages to the brain. Ziconotide locks calcium channels in nerve cells. This stops communication--and blocks pain. Ziconotide could soon be available as a prescribed treatment for chronic pain.

Scientists have also set their sights on toxins found in puffer fish of the family Tetraodontiformes (TEH-trah-OH-don-tih-forms). People pay big bucks to eat puffer fish--a delicacy in many countries. Some types of these fish pack high levels of the poison tetraodotoxin (teh-trah-OH-doh-TAHK-sihn). And about 100 daring diners die each year from downing fish containing the toxin. This chemical is 3,000 times stronger than morphine, but doctors think that in small amounts it could kill pain. Like the cone snail's ziconotide, puffer-fish poison targets chemical floodgates in nerve cells. But instead of blocking calcium, it bars sodium--another element needed to send pain signals to the brain.

FROG PHARMACY

Grant's frogs also show painkiller promise. For instance, the Epipedobates tricolor (eh-pee-PED-oh-BAY-tees TRY-cuh-lor), or phantasmal poison frog, contains the chemical epibatadine (eh-pee-BATE-uh-dyn). "The raw chemical is about 200 times more potent than morphine," says Grant. "It can't be used directly, but it provides chemists with a model for developing drugs."

No matter which poisonous species or toxin is tested, when it comes to judging these new drugs, no pain will mean all gain.

Nuts & Bolts

You hurt a shoulder. How does your body feel the pain?

1. OUCH! Your body is lined with nerves. These bundles of ceils release chemical signals when they sense anything from a tickle to tissue damage.

2. RELAY Sensory nerves zap electrical signals along specialized pain fibers. Nerve cells turn the signals into chemical-based packages and launch them across tiny gaps, or synapses, to nerve cells on the other side. This continues until the message reaches the spinal cord.

3. REACT once in the spinal cord, the message zooms through a series of relay stations to the areas of the brain that decode the signal as pain.

4. RELIEF When your brain recognizes the pain, it tells your body to react. The brain also triggers the release of chemicals that can interrupt the pain signal.

DID YOU KNOW?

* The toxin that covers some frog species' skin not only helps ward off predators, but also helps prevent harmful fungus and bacteria from growing on the frog. Because frogs live in moist environments, their skin is always wet--that's prime breeding ground for moisture-loving fungus and bacteria. Without the toxin to kill the growth, the frogs could get sick.

* There are about 30 billion nerve cells in the human body, but only 5 percent of them are active at any one time.

CRITICAL THINKING:

* What are the pros and cons of using animal toxins for medicine? (Hint: think about costs, ability to harvest the toxins, their usefulness, etc.)

CROSS-CURRICULAR CONNECTIONS:

Social Studies: Although a puffer fish contains deadly neurotoxins, it's a delicacy in many countries. Chefs in Japan must go through stringent training on how to remove the fish's poisonous parts before they are licensed to prepare and serve fugu, or puffer fish. Research and report on fugu preparation and eating in Japan.

RESOURCES

* Learn about frog toxins at: www.amnh.org/exhibitions/ frogs/ecosystem/drugstores.php

* Check out "Toxins to Treatment" at: www.portfolio.mvm.ed.ac.uk/studentwebs/session2/ group13/index.html

DIRECTIONS: Fill in the blanks to complete the following sentences.

1. When an enemy tries to eat the poison dart frog, the frog's toxin the nerves that control the enemy's--and--pumping.

2. The body system than includes the brain,--, and nerves, is called the system.

3. --, a drug for chronic pain sufferers, works by mimicking--, the body's own antipain agents. The down side: Patients can build up a--to the drug, so doctors have to give the patient more medicine.

4. When you get hurt, nerve cells called--carry electrical signals to the brain, and the brain recognizes these impulses as pain. In order for the nerve cells to perform this task, they require the help of these two elements:--and--.

1. paralyzes, breathing, blood

2. spinal cord, nervous

3. morphine, endorphins; tolerance

4, neurons; calcium, sodium
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Article Details
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Title Annotation:Life Nervous System
Author:de Seve, Karen
Publication:Science World
Date:Jan 3, 2005
Words:1380
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