A team of biologists at the University of California, Los Angeles claim to have transferred a memory from the brain of one sea snail to another, creating an artificial memory, basically injecting the RNA (ribonucleic acid) from one sea snail into the other. This research could lead to new ways to restore lost memories and possible treatments for diseases such as Alzheimer’s.
“I believe that in the not too distant future, we could potentially use RNA to enhance the effects of Alzheimer’s disease or post-traumatic stress disorder,” says David Glanzman, study leader who publishes the journal eNeuro.
RNA is a cellular messenger that makes proteins and carries out DNA instructions to other parts of the cell. It is now understood to have other key functions in addition to protein coding, including the regulation of a variety of cellular processes involved in development and disease.
Conch experiment
The researchers gave mild electric shocks to the tails of a species of sea snail called Aplysia . This marine invertebrate is characterized by having a nervous system with thousands of large neurons, which allows electrodes to be implanted with great ease. Thus, the snails received five electric shocks, one every 20 minutes, and then five more shocks 24 hours later to generate an annoying memory. The affected snails reacted by contracting their gills as a defensive gesture. The snails’ defensive reflex increased. Finally, the defensive contraction, which lasted 50 seconds, was not only produced by receiving shocks, but also by touch; that is, when the researchers tapped the back of the snails, they found that those who had received the electric shocks experienced a defensive contraction that lasted an average of 50 seconds, a simple type of learning known as “sensitization.”
Then, they extracted the RNA from the nervous system of the sea snails that had received the electric shocks and also from the control subjects. RNA from the first (sensitized) group was injected into seven sea snails that had not received any electrical shock, and RNA from the second group was injected into a control group of seven snails that had also not received any electrical shock.
The scientists found that those who had received the RNA from the sensitized snails behaved as if they had received the electric shocks themselves: they showed a defensive contraction that lasted an average of 40 seconds.
As expected, the control group did not show a very long contraction. Just 1 second.
The researchers then added the RNA to Petri dishes containing neurons extracted from various snails that did not receive electric shocks. Some of the plates contained sensory neurons, and other motor neurons, which in the snail are responsible for the reflex.
The experiment in the Petri dishes obtained the same result as in the live snails: the sensory neurons in the Petri dishes became more excitable with the electric shocks, something that did not happen with the motor neurons. Furthermore, adding RNA from a sea snail that was not shocked did not produce this increased excitability in sensory neurons.
In the field of neurology, memories are thought to be stored in synapses. According to Glanzman, ” If memories were stored in synapses, there would have been no way our experiment would have worked, ” adding that the sea snail is an excellent model for studying the brain and memories.
In the future, RNA may be used to awaken and restore memories that have been dormant in the early stages of Alzheimer’s disease.
Reference: RNA from Trained Aplysia Can Induce an Epigenetic Engram for Long-Term Sensitization in Untrained Aplysia, eNeuro, doi.org/10.1523/ENEURO.0038-18.2018
Image credit: Christelle Snow / UCLA
