Mar 16, 2020

Love hormone influences medaka’s mate preference: oxytocin works in a sex-specific manner
Published in Proceedings of the National Academy of Sciences

Oxytocin facilitates mating preference for a familiar individual in some monogamous species. Its function in non-monogamous species is, however, largely unknown. To address this issue, the research group led by Dr. Yokoi generated oxytocin mutant medaka and examined their behavior toward familiar or unfamiliar individuals. In the wild-type, medaka females can recognize and select visually familiarized males as their mating partner, whereas males show courtships indiscriminately. Oxytocin disruption made females lost this preference and oxytocin mutant females accepted the courtship from unfamiliar males soon. On the other hand, oxytocin mutant males showed little interest toward unfamiliar females but showed overly guarding behavior against familiar females from rival males. Although oxytocin is thought to facilitate affiliation toward familiar individuals in humans, this study revealed that oxytocin had a role of suppressing affiliation in medaka males. Oxytocin may have functions other than as “love hormone” depending on the species and sex of the animal.
In the brain of oxytocin mutant medaka, the expression amounts of many kinds of genes were different from those of non-mutant, and some of them were conserved between medaka and humans. It is hoped that basic research in medaka will reveal how oxytocin regulates attachment to familiar individuals and how it generates sex differences.

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Sexually dimorphic role of oxytocin in medaka mate choice.
Saori Yokoi, Kiyoshi Naruse, Yasuhiro Kamei, Satoshi Ansai, Masato Kinoshita, Mari Mito, Shintaro Iwasaki, Shuntaro Inoue, Teruhiro Okuyama, Shinichi Nakagawa, Larry J Young, Hideaki Takeuchi
Proceedings of the National Academy of Sciences of the United States of America 117(9) 4802 - 4808 2020

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Proceedings of the National Academy of Sciences