National Geographic Daily News
A great pond snail.
A great pond snail clings to a plant stem (file photo).

Photograph by Frank Greenaway, Getty Images

Brian Handwerk

for National Geographic News

Published June 3, 2010

Snails on speed don't get speedier—but their supercharged brains do learn better and make memories that last much longer, a new study says.

Scientists gave pond snails the amphetamine crystal meth to explore the memory-related brain processes that get humans so hooked on the drug.

(Related: "Cocaine on Money: Drug Found on 90 Percent of U.S. Bills.")

Human meth users experience sensations of happiness and high self-esteem that help make the drug extremely addictive. Scientists suspect that such cravings may be tied to powerful "pathological memories" that make such highs difficult to forget.

"We were not trying to addict the snails," said study co-author Barbara Sorg, a biochemist at Washington State University in Pullman. "We were trying to see how meth might create a better memory in the very early stages of the brain process."

Drugged Snails Remember Irritation

Pond snails don't have the memory skills of more complex creatures, but they can recall experiences and learn from them.

During the experiment, Sorg and colleagues put aquatic snails in tanks, some of which contained meth-laced water, and some that that contained regular water. As aquatic creatures, the snails breathe mostly through their skins, but will extend air tubes above the water's surface when oxygen is scarce.

Low-oxygen levels in the water caused the snails to extend their tubes. The researchers poked the tubes with sticks, irritating the animals, thus training them not to extend their tubes.

Snails not exposed to meth seemed to retain long-term memories of the "training" for only a few hours, at which point they would start raising their tubes again.

But snails exposed to meth recalled the poking more than 24 hours later and kept their tubes closed.

It isn't a total surprise that such "meth memories" persist, said Sorg, whose research appeared May 28 in the Journal of Experimental Biology.

"Amphetamines are given to humans for the purpose of focusing attention," she explained. "Ritalin, for example, is an amphetamine derivative given for treatment of ADHD."

Cracking Meth's Cerebral Code

Since snail brains are simple, any immediate correlation with humans would be premature, Sorg stressed. But human and snail brains share much of the same biochemistry.

For instance, studying a single brain cell that controls snail learning and memory behaviors could give insights into how both snail and human brains work, according to study co-author Ken Lukowiak of the University of Calgary in Canada.

"Our next step could be to look in that single cell and see the changes in chemistry when the snail learns under the influence of meth," Sorg said.

By cracking this cerebral code, scientists could someday find ways to help alter addictive behaviors in humans. (See: "Toxic Snail Venoms Yielding New Painkillers, Drugs.")

"We think it's a memory-based process that makes people crave the drug," Sorg said. "So how do you diminish those memories or specifically try to disrupt or diminish that memory?"

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