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The psychoactive drug known as ecstasy can make people more affectionate towards others, and a study released Thursday suggests that it has the same effect on octopuses.
Octopuses are almost entirely antisocial, except when they mate, and the scientists who study them must house them separately so as not to kill or eat each other. However, octopuses who received the drug known as MDMA (or ecstasy, E, Molly or a number of other slang terms) wanted to spend more time near other octopuses and even take them. in their arms.
"I was absolutely shocked that this had this effect," said Judit Pungor, a neuroscientist at the University of Oregon who studies octopuses but was not part of the "University of Oregon". Research Team.
Eight-legged invertebrates are separated from humans by more than 500 million years of evolution, says Pungor. The closest relatives of octopus are creatures like snails and slugs, and their brains have a host of strange structures that have evolved on a path completely different from that of the human path.
"They have that complex brain that they've built, which has absolutely no activity like ours – but here they show that's the case," Pungor says. "The fact that they induced this very soft and very gentle behavior is really fascinating."
The idea of testing the effect of the drug on octopus came from Gul Dolen, a neuroscientist from Johns Hopkins University.
"My lab has been studying MDMA for a long time," she says, "and we have developed many neural mechanisms that allow MDMA to have these very profound social effects.
Dolen's is interested in octopus a few years ago when scientists sequenced the complete genetic code of a creature known as California's two-dot octopus.
It turns out that octopuses and people have nearly identical genes for a protein that binds the serotonin signaling molecule to brain cells. This protein is also the target of MDMA, so Dolen wondered how the drug would affect this generally unfriendly animal.
"The mere fact of having protein," she says, "does not mean that when MDMA binds to protein, it will do something like in humans or mice."
To find out, she and Eric Edsinger, a colleague at the Marine Biology Lab at Woods Hole, Mass., First had to figure out how to give ecstasy to the octopus. They placed the creatures of the size of a hand in a cup filled with seawater and MDMA, so that the octopus could absorb the drug through their gills.
The researchers started with high doses of the drug just to see if it had an effect on the octopus.
"They did not really like it, they looked scared," Dolen said. "They were just taking these super hypervigilance postures, sitting at the corner of the tank and watching everything."
But lower doses – the type a person can take – have led to a profound change in behavior.
The researchers knew from previous tests that an octopus would normally stay away, far from a second. the octopus that was confined in a small cage inside the first tank. But an octopus on MDMA would approach the new neighbor.
"They spent a lot more time on the side of the tank, the chamber, which contained the other octopus," says Dolen.
Moreover, without the drug, any octopus that was approaching from abroad would remain very reserved, perhaps only extending to an arm to touch the cage of the animal. other animal.
"After the MDMA, they were essentially tight," explains Dolen, who explains that the octopuses were "really more relaxed in their posture and use their bodies a lot to interact with other octopus".
For her, the results published in the journal Current Biology show that "serotonin has been encoding social functions for a very, very long time – at least 500 million years ago, it started doing this job".
Zachary Mainen, a neuroscientist at the Champalimaud Center for the Unknown in Portugal, points out that some research done decades ago has shown that giving extra serotonin to lobsters can alter their social behavior.
"Specifically," says Mainen, "if you give them more serotonin, they will become more dominant.A small lobster that has been given serotonin will become a more aggressive and socially dominant lobster."
He says that MDMA, which affects the serotonergic system, clearly affects the social behavior of octopus, but he does not know if it really induces greater love for another creature.
"Is it really affection, how would we know?" Mainen asks. "It's quite fascinating and super suggestive, but I'm not 100 percent convinced that it's the same thing in octopus and in humans."
Still, he thinks it's amazing that this drug has similar behavioral effects.
"I like the fact that they have shown that a species so foreign to us as an octopus has a molecule, a serotonin transporter, that can be affected by a drug that affects us, and that the drug has a similar effect on the octopus, "says Mainen.
"It shows us how much we do not know and how much there is to understand."
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