A microscope image of Hydra vulgaris, magnified 40 times. Credit: Corvana/ CC BY-SA 3.0.
Italian researchers used a simple semiconducting organic molecule to modulate the neural activity in a fresh-water polyp to control a specific behaviour. When added to water in a tank the compound, called ETE-S, acts on the neurons of the invertebrate, which is only a few millimetres long, and triggers it to twist its tentacles.
The study, by Claudia Tortiglione and colleagues at the Institute of Applied Sciences and Intelligent Systems, of the National Research Council (CNR) in Pozzuoli, adds to their aim of developing new neuroelectronic interfaces that could one day be applied to the treatment of neuronal disorders and motor dysfunctions, or to control prosthetic limbs.
“We use the fresh-water polyp Hydra vulgaris as a model, because it has a very simple anatomy,” Tortiglione explains. “Its body is a soft hollow tube with a nerve net extending over the entire surface, thin tentacles protruding from the top and a peduncle ending”.
The researchers in Pozzuoli found out that ETE-S, a semi-conducting compound made of oxygen, sulphur and sodium, affects the electrical activity of Hydra’s neurons and induces specific movements: it slows the usual rhythmic contractions of the cylindrical body and elicits tentacle writhing, a behaviour that the invertebrate typically exhibits when eating. The movements’ pattern returns to normal in 25-30 minutes. The discovery is described in Science Advances1.
Tortiglione’s team, with help from researchers from Linkoping University, in Sweden, had previously demonstrated2 that specific cells located on the polyp’s peduncle produce an enzyme that induces ETE-S to form electronically conducting wires that become embedded in the living tissue of the animal, making it a bionic organism. These self-organized electronic components could be used for neurostimulation or as entry points to connect the nervous system to electronic devices, offering an alternative to current invasive methods.
The work could pave the way for new clinical mini-invasive applications and wireless tools to record and modulate neural activity. The next step will be to study the relationships between similar molecular structures and different induced behaviours, to design organic electrodes that can enhance or diminish the activity of specific neural networks.
