Worms sniff out harm

Worms learn: If something makes you sick, don't eat it again.

By | December 5, 2005

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Worms learn: If something makes you sick, don't eat it again. Researchers at Rockefeller University have found that worms can learn to avoid substrates scented with bacteria that have made them ill in the past.1 The neuro-transmitter serotonin, which mediates nausea and food aversions in humans, appears to control this aversion.

Researchers in Cori Bargmann's lab raised Caenorhabditis elegans either on a harmless strain of bacteria or on plates that also held an additional, toxic strain. Naïve worms that had never been infected by harmful bacteria failed to avoid them, but C. elegans that had previous contact with pathogenic bacteria preferred the harmless kind.

Serotonin appears to mediate which scent C. elegans prefers. Researchers showed that mutant C. elegans unable to synthesize serotonin, and those lacking a specific serotonin receptor, failed to learn to avoid harmful bacteria.

This serotonin-based system detection system is found in nearly every animal studied so far, says Columbia University neuroscientist Michael Gershon. In humans, most serotonin is made in cells lining the intestines, not in the brain, he says. When released, serotonin induces the queasiness we associate with intestinal distress.

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