Okayama University When rats scratch their eyes, there is a "dominant foot"

National University Corporation Okayama University
[Okayama University] When rats scratch their eyes, there is a “dominant foot”
October 25, 2022
National University Corporation Okayama University
https://www.okayama-u.ac.jp/
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-Points of announcement-
When the rats scratched their eyes, they revealed that they were “right-footed.” In recent years, it has been reported that a neuropeptide called gastrin-releasing peptide (GRP) and its receptor function as an itch-specific transduction molecule in the mouse spinal cord. In this study, we also identified that itching in the facial region is transmitted by the GRP system present in the medulla oblongata. The elucidation of the mechanism of action that conveys itching through the eyes is expected to contribute to the development of new treatments for intractable pruritus of the eye, including hay fever. ◆Overview
Associate Professor Hirotaka Sakamoto (Neuroendocrinology) of National University Corporation Okayama University (Headquarters: Kita-ku, Okayama City; President: Hiroshi Makino), Academic Research Faculty of Natural Sciences (Ushimado Rinkai), and Nara Women’s University Research Faculty of Life and Environmental Sciences A research group led by Associate Professor Keiko Takanami (Behavioral Neuroscience) (Former Assistant Professor at the National Institute of Genetics) in the Department of Lifestyle and Health Sciences has found that when rats are stimulated with histamine in both eyes, they scratch their eyes mainly on the right side. (i.e., the “dominant foot” when rats scratch their eyes). Furthermore, in recent years, it has been reported that a neuropeptide receptor called the gastrin-releasing peptide (GRP) receptor functions as an itch-specific transduction molecule in the mouse spinal cord.
This time, we also identified that itching in the facial region is transmitted by the GRP system present in the medulla oblongata. These research results were published online in “Proceedings of the Royal Society B: Biological Sciences” on October 19, 2022 (00:01am UK time). Itchy eyes are a very unpleasant sensation caused mainly by
inflammation of the conjunctiva. Unlike itchy skin that comes from any part of the body, rubbing your eyes is not a good idea and can damage the delicate conjunctival epithelium. We have studied the less well-studied neural basis of ocular itch transmission compared to the spinal nervous system that conveys itch in the body. As a result, it was found that when both eyes were stimulated in rats, the right hind paw scratched the eyes (in other words, the paw used to scratch the eyes was the “right-handed” rat).
In rodents, it is known that the GRP system of the spinal cord and somatosensory system is involved in the itch sensation from most parts of the body. , was also shown to be important for the transmission of itch originating from the eye.
Focusing on “GRP receptor-expressing neurons” and clarifying the mechanism of action of the GRP system in the medulla
oblongata/trigeminal nerve sensory system, which conveys itching from the eyes, is a new treatment for intractable pruritus of the eye, including hay fever. It is hoped that this will also contribute to the development of legislation.
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Figure 1. Itching in the body is transmitted through the spinal sensory nervous system. On the other hand, it has been thought that itching in the facial region, including the eyes, is transmitted via the trigeminal sensory system. This time, we have clarified that the GRP system is commonly involved in both the spinal cord (body) and medulla oblongata (face) levels.
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Figure 2. (a) Saline (control) or histamine was administered bilaterally to the eyes of rats. Number (b) and time (c) of hindpaw scratching for 60 minutes after administration of saline or histamine *P < 0.05 with Wilcoxon signed rank test. ◆ A word from researchers -Associate Professor Hirotaka Sakamoto, Faculty of Science, Okayama University (Ushimado Rinkai)- "I'm right-handed." Certainly, the right hand will come out immediately no matter what you do. Oh my God! ? I was very surprised to learn that most rats are right-handed (feet) when scratching their eyes. It seems like yesterday that I hurriedly wrote my thesis, saying to myself, "So, Rat, you too?" It is hoped that this result will shed light on the neural basis of human handedness and its evolutionary process. [Image 4

Associate Professor Hirotaka Sakamoto
-Associate Professor Keiko Takanami, Nara Women’s University, Faculty of Life and Environmental Sciences-
Even if we know in our head that we shouldn’t rub our eyes, we rub our eyes and scratch when we feel itchy. Especially children cannot stop scratching. Until now, we have analyzed the neural circuit that transmits itchy eyes, and this time, we were able to clarify that the GRP receptor of the trigeminal sensory system is actually involved in the transmission of itchy eyes. I was. We hope that this will lead to the development of treatments for itchy eyes such as hay fever in the future.
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Associate Professor Keiko Takanami
◆ Paper information
　Paper title: Footedness for scratching itchy eyes in rodents “When rodents scratch their eyes, there is a dominant leg”
　Published in: Proceedings of the Royal Society B: Biological Sciences Authors: Yukitoshi Katayama#, Ayane Miura#, Tatsuya Sakamoto, Keiko Takanami* and Hirotaka Sakamoto* (#equal contribution, *corresponding author)
　doi: 10.1098/rspb.2022.1126.
URL: https://doi.org/10.1098/rspb.2022.1126
◆ Research funds
This research was carried out with the following support.
・Japan Society for the Promotion of Science (JSPS) Grant-in-Aid for Scientific Research on Innovative Areas (Research area proposal type) (Academic research support infrastructure formation) Advanced bioimaging support platform (ABiS) 16H06280 Research co-investigator: Hirotaka Sakamoto
・JSPS Grants-in-Aid for Scientific Research Fund for the Promotion of Joint International Research (Fostering Joint International Research) 15KK0343 Principal Investigator: Keiko Takanami
· JSPS Grants-in-Aid for Scientific Research, Basic Research (C) 19K06475 Research Representative: Keiko Takanami
・JSPS Grants-in-Aid for Scientific Research, Basic Research (B) 21H02520 Principal Investigator: Tatsuya Sakamoto
・JSPS Grant-in-Aid for Scientific Research on Innovative Areas (Research area proposal type) (Singularity biology) 21H00428 Research representative: Tatsuya Sakamoto
・Kenzo Suzuki Memorial Medical Science Applied Research Foundation Disease-Specific Research Grant 19-085 Research co-investigator: Hirotaka Sakamoto
◆ Detailed research content
When rats scratch their eyes, there is a “dominant foot”
　https://www.okayama-u.ac.jp/up_load_files/press_r4/press20221024-1.pdf ◆ Reference
・Graduate School of Science and Technology, Okayama University 　https://www.gnst.okayama-u.ac.jp/
・Okayama University Faculty of Science
　https://www.science.okayama-u.ac.jp/
・Ushimado Marine Biological Station, Faculty of Science, Okayama University 　https://www.science.okayama-u.ac.jp/~rinkai/
・Nara Women’s University
　http://www.nara-wu.ac.jp/index.html
◆ Reference video: Introduction to the Ushimado Critical Laboratory, Faculty of Science, Okayama University (YouTube 3:05)
　https://youtu.be/t7jJWOBHxEk
[Video 2: https://prtimes.jp/api/movieim.php?url=www.youtube.com/watch?v=t7jJWOBHxEk]

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Ushimado Marine Biological Station, Faculty of Science, Okayama University (Setouchi City, Okayama Prefecture)
◆ Inquiries regarding this matter
Hirotaka Sakamoto, Associate Professor, Department of Natural Sciences (Rinkai Ushimado), Faculty of Science, Okayama University
　Ushimado Marine Biological Station, Faculty of Science, Okayama University 130-17 Shikanoshi, Ushimado-cho, Setouchi City, Okayama Prefecture 701-4303
　TEL: 0869-34-5210
　FAX: 0869-34-5211
　http://www.science.okayama-u.ac.jp/~rinkai/index.html
Associate Professor Keiko Takanami, Nara Women’s University
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Public Relations Division, General Affairs and Planning Department, Okayama University
Nara Women’s University, General Affairs Division, Public Relations and Fund Section
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