Octopuses given mood drug ecstasy reveal genetic link to changes in human social behavior – sciencedaily


By studying the genome of a kind of octopus that is not known for being kind to its peers, and then testing its behavioral response to a popular mood-modifying drug called MDMA or “ecstasy,” scientists say they have found preliminary evidence of an evolutionary link between the social behaviors of the sea creature and humans, species separated by 500 million years on the evolutionary tree.

A summary of the experiences is published on September 20 in Current biology, and if the results are validated, the researchers say, they could open up opportunities to accurately study the impact of psychiatric drug therapies in many animals distant from humans.

“The brains of octopuses are more similar to snails than that of humans, but our studies add to the evidence that they can exhibit some of the behaviors that we can,” says Gül Dölen, MD, Ph.D., assistant professor neuroscience. at Johns Hopkins University School of Medicine and the principal investigator conducting the experiments. “What our studies suggest is that certain brain chemicals, or neurotransmitters, that send signals between neurons necessary for these social behaviors are conserved throughout evolution.”

Octopuses, says Dölen, are well known to be intelligent creatures. They can trick their prey into getting into their claws, and Dölen says there is evidence that they also learn by observation and have episodic memories. Gelatinous invertebrates (animals without a backbone) are also known to escape from their reservoir, eat other animals’ food, evade guardians, and sneak around.

But most octopuses are asocial animals and avoid others, including other octopuses. But because of some of their behaviors, Dölen still believed that there may be a connection between the genetics that guide social behavior in them and in humans. One place to look was in the genomics that guide neurotransmitters, the signals that neurons pass between themselves to communicate.

Dölen and Eric Edsinger, Ph.D., a researcher at the Woods Hole, Mass., Marine Biological Laboratory, took a closer look at the genomic sequence of Octopus bimaculoides, commonly referred to as the California two-point octopus.

Specifically, in the genetic regions that control how neurons hook neurotransmitters to their membranes, Dölen and Edsinger found that octopuses and humans had almost identical genomic codes for the transporter that binds the neurotransmitter serotonin to the membrane of the body. neuron. Serotonin is a well-known mood regulator and closely linked to certain types of depression.

The serotonin binding transporter is also known to be where the MDMA drug binds to brain cells and alters mood. Thus, the researchers set out to see if and / or how octopuses react to the drug, which also produces so-called pro-social behaviors in humans, mice and other vertebrates.

Dölen designed an experiment with three connected water chambers: one empty, one with a plastic figurine under a cage, and one with a female or male octopus raised in the laboratory under a cage.

Four male and female octopuses were exposed to MDMA by placing them in a beaker containing a liquefied version of the drug, which is absorbed by the octopuses through their gills. Then they were placed in the experimental chambers for 30 minutes. All four tended to spend more time in the room where a male octopus was caged than the other two rooms.

“It’s not just quantitatively more time, but qualitatively. They tended to hug the cage and put their mouthparts on the cage,” Dölen explains. “It’s very similar to how humans react to MDMA; they touch each other frequently.”

Under normal conditions, without MDMA, five male and female octopuses avoided only male octopuses in cages.

Dölen says that the experiments suggest that the brain circuits guiding social behavior in octopuses are present under normal conditions, but can be suppressed by natural or other circumstances. “Octopuses will suspend their antisocial behavior for mating, for example. Then, when they are done mating, they will go into aggressive and asocial mode,” says Dolen.

Dölen warns that the results are preliminary and must be replicated and confirmed in further experiments before octopuses can be used as models for brain research.

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