In a scientific first, researchers claim to have transferred memories between sea snails by injecting RNA from a trained sea snail into one that hasn't been trained - and observing the trained response in the second snail. This research could lead to new ways to lessen the trauma of painful memories with RNA and to restore lost memories.
The sea hare is a well understood model species in neurobiological studies, with a pedigree reaching back to Nobel laureate E. R. Kandel's research on learning and memory in the 1960s. They received one shock every 20 minutes, five times in a row followed by five more after 24 hours.
When researchers tapped the snails afterward, those that had received the shock training contracted their bodies into a defensive posture for an average of around 50 seconds - but the snails that had not been trained only contracted for about one second.
When touched lightly on the siphon, the neurons fire, retract the tissue, and contract the gill within the body cavity for a few seconds to protect it against attack. This isn't as hard as it sounds - they simply applied a mild, but still unpleasant, electric shock to the tails of a sea snail called Aplysia californica.
After sensitising the sea snails, Glanzman extracted RNA from the animals and injected it into other sea snails to see what happened.
The non-sensitised snails injected with the RNA from the shocked animals behaved as if they had themselves received the tail shocks, displaying a defensive contraction of about 40 seconds.
Glanzman wanted to know if the RNA from shocked snails actually affected the neuronal connections of the snails receiving the injections any differently than RNA from nonshocked snails.
When a marine snail is given electric tail shocks, its sensory neurons become more excitable. So, in a third test, he and his team removed sensory neurons from nonshocked snails, cultured the cells in a dish, and then exposed the cells to RNA from shocked snails. The memory is not stored in the RNA itself, he speculates-instead, noncoding RNA produces epigenetic changes in the nucleus of neurons, thereby storing the memory.
"If memories were stored at synapses, there is no way our experiment would have worked", he said.
According to the researchers, the experiments show how essential parts of the memory trace, or engram, that gives rise to sea hare sensitisation are held in RNA, rather than in the connectivity of brain cells as traditional neuroscience dictates.
He also stressed that the snails did not get hurt: "These are marine snails and when they are alarmed they release a handsome purple ink to hide themselves from predators".