'Memories' Transferred From One Snail to Another Via Injection, Scientists Say

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The research that was published in the Journal eNeuro can now provide better ideas about the search for the physical basis of memory. If confirmed in other species, the finding may lead to a shift in scientists' thinking about how memories are made-rather than cemented in nerve-cell connections, they may be spurred on by RNA-induced epigenetic changes. Several years ago, though, he and his colleagues began replicating memory-erasing research done in rodents in California sea hares (Aplysia californica), a type of marine snail also called a sea slug. Normally, these snails only contract for one second.

As it turned out, the RNA samples retained the memory of the electric shock, causing the untrained snails to exhibit a defense mechanism that lasted nearly as long as that of the donor snails.

They then extracted RNA from the gastropods and injected them into a group of untrained snails, who behaved in a similar manner to the shocked animals by displaying a defensive contraction that lasted an average of about 40 seconds.

The researchers trained one cohort of the molluscs to exhibit a defensive reflex when their tails were stimulated by mild electric shocks. The scientists removed the RNA from the nervous systems of the snails and injected it into the marine snails that never showed sensitization ever before.

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The RNA in the trained snail was used to create an engram - the elusive substrate of memory - by sensitising them with tail simulation that triggers an involuntary defensive reflex. "If circulating neural RNAs can transfer behavioral states and tendencies, orchestrating both the transient feeling and the more permanent memory, it suggests that human memory-just like mood-will only be explained by exploring the interplay between bodies and brains". They bathed the untrained neurons in RNA from trained cells, then gave them a shock, and saw that they fired in the same way that trained neurons do. But scientists have been studying sea snails for a long time, and they know an very bad lot about how the organisms learn.

Glanzman said the next step in this research is to transfer RNA in more complex animals, like mice. The experiments should also be replicated in organisms other than snails, he says. Zapping the culture with a bit of current excited the sensory neurons much more than neurons treated with RNA from nonshocked snails. He said that if the memories were held in the synapses that the experiment would not have been able to work.

Scientists know more about the cell biology of this simple form of learning in this animal than any other form of learning in any other organism, Glanzman said.

Despite having numerous differences, there are a number of similarities as well when you look at the way how snail nerve cells actually work and how the human cells function. Biologists believe that in the future this method can be used to recover memories lost in the early stages of Alzheimer's disease.

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