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Alkman
Saturday, March 11th, 2006, 11:52 AM
Toxin in absinthe makes neurons run wild



In the late 20th century, espressos and caffe lattes became available on every urban street corner. In late 19th-century Paris, absinthe was the favored drink of artists and writers. Some say addiction to the emerald-green liqueur drove Vincent Van Gogh to take his own life. Edgar Degas, Henri de Toulouse-Lautrec, and Pablo Picasso all painted absinthe drinkers, capturing both the drink's popularity and its dark side.

Doctors at the time recognized that absinthe can cause convulsions, hallucinations, and psychotic behavior. Now, researchers at the University of California, Berkeley and Northwestern University Medical School in Chicago have learned how the drink's toxic component wreaks its neurological effects.

They found that the toxin, alpha-thujone, blocks brain receptors for gamma-aminobutyric acid, or GABA. Without access to GABA, a natural inhibitor of nerve impulses, neurons fire too easily and their signaling goes out of control.

"This paper is very important because it gives the biochemical mechanism for toxicity," says biochemist Wilfred Niels Arnold of the University of Kansas Medical Center in Kansas City.

Berkeley researchers Karin M. Hφld, Nilantha S. Sirisoma, and John E. Casida collaborated on the study with Tomoko Ikeda and Toshio Narahashi of Northwestern. The group's results, reported this week at the American Chemical Society meeting in San Francisco, will appear in the April 11 Proceedings of the National Academy of Sciences.

Scientists had documented thujone's effects by 1916, but "nobody had ever figured out exactly where the toxin was working," says Hφld. She and her colleagues conducted tests on fruit flies, mice, and rat neurons to connect alpha-thujone to GABA receptors. They also examined how animals' liver enzymes break down the compound.

Despite doctors' warnings about the dangers of absinthe, the beverage became very popular, especially in France. Between 1905 and 1913, Belgium, Switzerland, the United States, and Italy cracked down, banning the liqueur. France followed in 1915.

In some countries, notably the Czech Republic, absinthe is still available, albeit in a less potent form. Old absinthe contained about 260 parts per million of alpha-thujone, says Arnold. "Present-day absinthe generally has less than 10 parts per million," he says, which is below the maximum concentration permitted by European beverage guidelines. In today's absinthe, "the most toxic compound is the alcohol," quips Arnold.

Alpha-thujone comes from the herb wormwood, which flavors absinthe. Although few people now drink the liqueur, "a lot of herbal preparations are available on-line, and one is wormwood oil," says Hφld. People have used this oil since antiquity to treat digestive disorders. The alpha-thujone concentration in the oil is much higher than in absinthe and is a greater potential health concern, says Hφld.

Research into absinthe waned after its prohibition, Arnold notes. However, these new results reveal potential uses for alpha-thujone. "A lot of insecticides work on GABA receptors," notes Hφld.

Another group at Berkeley is planning to study long-term effects of the compound in rodents, she adds. That work may provide important information for modern-day absinthe drinkers who ingest low toxin doses over a lifetime.




Corinna Wu





References:

Hφld, K.M., et al. 2000. a-Thujone and absinthe: Structural and metabolic aspects of neurotoxic action. American Chemical Society National Spring Meeting. March 26-30. San Francisco.

Hφld, K.M., N.S. Sirisoma . . . and J.E. Casida. 2000. a-Thujone (the active component of absinthe): y-Aminobutyric acid type A receptor modulation and metabolic detoxification. Proceedings of the National Academy of Sciences 97(April 11):3826-3831. Abstract available at http://www.pnas.org/cgi/content/abstract/97/8/3826.




Further Readings:

Arnold, W.N. 1989. Absinthe. Scientific American 260(June):112-117.

Bower, B. 1999. Gene tinkering hikes fear and anxiety in mice. Science News 156(Sept. 4):149. Available at http://www.sciencenews.org/sn_arc99/9_4_99/fob4.htm.

______. 1995. Schizophrenia: Fetal roots for GABA loss. Science News 147(April 22):247.

Carpenter, S. 1999. Fever-induced seizures cause brain changes. Science News 156(Aug. 7):86.

Weisbord, S.D., et al. 1997. Poison on line—acute renal failure caused by oil of wormwood purchased through the Internet. New England Journal of Medicine 337(Sept. 18):825-827.




Sources:

Wilfred Niels Arnold
Department of Biochemistry
University of Kansas Medical Center
Kansas City, KS 66160-7421

Karin M. Hφld
Environmental Chemistry and Toxicology Laboratory
Department of Environmental Science, Policy, and Management
University of California, Berkeley
Berkeley, CA 94720-3112

Blutwölfin
Saturday, March 11th, 2006, 12:56 PM
I thought that the "modern" Absinthe isn't as "dangerous" as the old one (except some strange brands from the Czech maybe.. :D )? At least I have never experienced hallucinations or something similar by drinking even two r three glasses of Absinthe.

Weg
Saturday, March 11th, 2006, 01:10 PM
I thought that the "modern" Absinthe isn't as "dangerous" as the old one (except some strange brands from the Czech maybe.. :D )? At least I have never experienced hallucinations or something similar by drinking even two r three glasses of Absinthe.

True. No risk to turn mad any more with the modern recipe.