(ORDO NEWS) — Experiments on rats have shown that eye scratching is based on the same signaling pathways as skin scratching, although they pass through different nerves.
In addition, this reaction allows you to quickly distinguish between right-handed and left-handed animals.
Painful scratching accompanies many skin diseases, and these processes are actively investigated by scientists and physicians.
In particular, not so long ago, a protein receptor was identified that causes a sensation of unbearable itching. However, not only the skin can itch: from time to time everyone wants to rub their eyes.
Such movements have a protective function: they allow you to remove the motes that have fallen on the cornea and cause lacrimation, which washes away irritating substances.
The mechanisms underlying this behavior are far less well understood than skin scratching. This issue is the subject of a new work by Japanese scientists led by Okayama University professor Hirotaka Sakamoto.
The authors of the study conducted experiments with laboratory rats, causing them eye irritation by instillation of histamine, a substance that signals the development of allergic and inflammatory reactions.
The first experiments showed that histamine triggers scratching with the back paw on the same side of the body as the eye, which itches.
However, the right hind paw turned out to be more preferable: when histamine was instilled into both eyes, the animals used only it for scratching. Most likely, this is due to their natural “right-handedness”.
During skin scratching, the GRP-GRPR signaling pathway, which includes the gastrin-releasing neuropeptide and its receptors in spinal cord neurons, plays a key role.
Therefore, studying eye scratching, scientists focused on it. Experiments on the same rats showed that eye stimulation with histamine stimulated the activity of GRPR-containing cells.
The main role in this was played by neurons located in the gasser ganglion , the node of the trigeminal nerve, which is responsible, in particular, for the sensitivity of the skin of the face.
If the activity of these cells was artificially suppressed with the help of toxins, then the animals scratched the irritated eye much less frequently than usual.
Scientists believe that the results obtained will help in the treatment of painful itching of the eyes, and the instillation of histamine will become a convenient tool for quickly determining “left-handed” and “right-handed” in laboratory animals.
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