How poisonous is the Gympie Gympie tree

Plants: the nerve poison of the super nettle deciphered

Australian nettles are particularly nasty: their stinging hairs not only cause severe pain - it also lasts for hours, days or even weeks. The cause is protein molecules, the structure of which is similar to the poisons of spiders and cone snails, reports a team led by pharmacologists Irina Vetter and Thomas Durek from the University of Queensland. The team now writes in the journal "Science Advances" that the mechanism of action is similar. This is what the working group concludes from their analyzes of the protein molecules they call gympietides, which they extract from the stinging hairs of Dendrocnide excelsa and a related Australian nettle species.

In experiments with cell cultures, the team led by Vetter and Durek found that the Gympietide apparently open certain channels in the membrane of the nerve cells of their victims. The sodium ions flow into the interior of the cell - an action potential arises, a nerve impulse. Normally this excitation signal is reduced again after a short time. But not when the nettle peptides are involved: They no longer release the nerve cells so that they constantly send their signal. Those affected perceive this as pain.

The name of the fabrics is derived from »Gympie«, as the indigenous population of Australia calls their native nettles, which grow as bushes or trees. Dendrocnide excelsa can be up to 35 meters high. The leaves and stems are covered in trichomes, hair-like structures that look soft and felt-like. In truth, however, they are pointed - and bulging with toxins. When they touch the skin of humans or animals, they act like hypodermic needles.

What causes the unusually long-lasting pain, however, has so far been a mystery. Until now, experts thought that signal substances or inflammation-promoting substances contained in the trichome fluid were the cause; However, researchers were unable to explain the exact mechanism. Last but not least, the symptoms could not be reproduced with the substances previously suspected.

But with the newly discovered gympietids: mice that the team had injected the compounds with licked, bit or shook the affected paw for at least an hour. Similar active ingredients are so far only known from the animal world. Gympietides are the first plant-based example of such neurotoxins, writes the research team. This suggests that this principle of action developed independently of one another in plants and animals.