日本動物心理学会第84回大会 会員企画特別シンポジウム
ラリー・ヤング博士メモリアルシンポジウム: オキシトシンが紡ぐ社会的絆
（Dr. Larry J. Young Memorial Symposium: Oxytocin and Social Bonding ）
企画趣旨
米国エモリー大学教授Larry J. Young博士は、つくば市に滞在中の2024年3月に急逝されました。数多くの先駆的、独創的研究に影響を受けてきた世界中の研究者は未だ深い悲しみ包まれています。日本への愛と気さくな人柄から、数多くの来日の際には、さまざまな分野、世代の研究者と交流してこられました。本学会大会においても、2015年（第75回、日本女子大学）、2020年（第80回、鹿児島大学）の2回、特別講演をされています。長年にわたるハタネズミのPair Bonding行動の分子神経内分泌基盤の研究を通してYoung博士が一貫して主張してきた社会的絆形成・維持に果たすオキシトシンの役割、重要性は、ヒトを含む多様な動物種での研究を促し、社会性の神経基盤の理解を大きく進展させました。本シンポジウムでは、５名の演者の方々に、現在のご自身の研究を中心に動物心理学分野の研究におけるYoung博士の功績を振り返るとともに、それらをもとにした今後の研究の方向性について語っていただきます。
企画者
小川園子（筑波大学行動神経内分泌学研究室）
講演者
はじめに：小川園子（筑波大学行動神経内分泌学研究室）
Dr. Larry J. Young passed away in March 2024 while he was staying in Tsukuba City. We are still in deep sadness with the sudden loss of a prominent scientist and long-term friend. His research has been recognized world-wide by researchers in basic behavioral and biological sciences as well as in clinical psychiatric and gynecological sciences. Particularly, his research on molecular brain mechanisms of pair boding in Prairie voles from evolutionary perspectives opened a door to a new research field of brain oxytocinergic regulation of social behavior not only in rodents but also various other species, including humans. Throughout his scientific career, he traveled around the globe and gave numerous talks and lectures, including two special lectures in the annual meetings of the Japanese Society of Animal Psychology in 2015 and 2020. He inspired both experienced scientists and young students through his lectures, research papers, and his motto to positively enjoy one’s life. In this symposium, we will overview his research accomplishments under the theme of “oxytocin and social bonding.” Five speakers will discuss how Dr. Young’s findings on oxytocin functions influenced their own research on neural and neuroendocrine bases of social behavior in rodents, medaka fish, dogs, primates, and humans. This symposium will help us to appreciate Dr. Young’s outstanding life achievements and motivate us to continue our own research activities toward understanding of social behavior.
演題１：進化的視点から社会行動の神経内分泌学的基盤を考える
富原一哉（鹿児島大学法文学部人文学科心理学コース）
Voles (Microtus) have many subspecies, making them a valuable model for investigating the role of ecological differences in the evolution of behavior. Prairie voles (M. ochrogaster) are monogamous, and once a pair bond is formed, it persists for almost their entire lifetime. In contrast, American voles (M. pennsylvanicus) exhibit a promiscuous breeding pattern and establish isolated territories. Dr. Larry Young has demonstrated that this breeding pattern can be altered by regulating the expression of oxytocin (OT) and vasopressin (VP) receptors. Additionally, the OT/VP peptide family is found in vertebrates and some invertebrates and is believed to be one of the most ancient peptide hormones, emerging early in evolutionary history. The shared and species-specific roles of these peptides in social behavior suggest an evolutionary basis for behavior. In recent years, Dr. Larry Young has extended his research across multiple species, focusing on the evolution of social behavior, which may have been an inevitable direction for his work.
演題２：マウス性社会行動におけるオキシトシン・バソプレシンによる神経調節
近藤保彦（帝京科学大学生命環境学部アニマルサイエンス学科）
Dr. Larry Young’s research on pair-bonding in prairie voles has demonstrated that oxytocin and vasopressin function as critical neuromodulators in the brain. These findings have since been expanded to include research in laboratory rats and mice, in addition to voles. Mice lacking the oxytocin gene have been shown to exhibit deficits in social recognition, which is now considered one of the key functions of the social brain. Our current research has also demonstrated that oxytocin is essential for the preference for sexual odors. Moreover, a study on the preference for soiled bedding of opposite-sex conspecifics has revealed the possibility of cross talk between oxytocin and vasopressin receptors. As a result, investigations into the role of oxytocin and vasopressin in social behavior are now expanding beyond voles to encompass all mammalian species.
演題３：メダカから探るオキシトシン機能の進化的起源
竹内秀明（東北大学大学院生命科学研究科）
Our study focuses on the molecular mechanisms underlying sexual dimorphism in mating strategies using the Japanese medaka (Oryzias latipes) as a model organism. Medaka females visually discriminate between familiar and unfamiliar males and prefer to mate with familiar ones. Males, however, court indiscriminately regardless of familiarity. Previously, we demonstrated that oxytocin plays a crucial role in generating sexual dimorphism in medaka mating strategies. Oxytocin-mutant females lost their mate preference, while males acquired a preference for familiar females, revealing a sex-specific and inverse effect of oxytocin mutation. Furthermore, we discovered that male mating opportunities can modify male mating strategies. Naive males with no prior mating experience could remember females with sexual experience and exhibited mate preference. Interestingly, females also recognized naive males and selectively increased their mating receptivity. These findings suggest that males with limited mating opportunities can adapt their mating strategies. We are currently investigating the potential involvement of oxytocin in this mating opportunity-dependent modification of mating strategies.
演題４：ヒトとイヌの絆形成
菊水健史（麻布大学獣医学部）
The dog (Canis familiaris) was the first animal to be domesticated, with hundreds of different dog breeds recognized today. During the domestication process, dogs were subjected to a strong selection process according to their temperament, behavior, and cognitive abilities. Dogs are skilled at understanding human communicative gestures compared with wolves and chimpanzees. They even look back at humans when encountering unsolvable tasks, while wolves do not. These findings suggest that dogs acquired their unique cognitive abilities during domestication. These human-like unique abilities might also be related with interspecies’ bonding, namely human-dog bonding. Dogs can distinguish between individual humans and show distinctly different behaviors to caregivers compared with hand-raised wolves. We revealed that dog showed oxytocin mediated positive-loop for forming bonds with humans, and wolves did not show this positive loop with humans, suggesting that dog have acquired biological bond mechanisms in the process of domestication. Behaviors associated with oxytocin-mediated dog-owner bonding are observed when dogs reunite with the owners. During this reunion scene, the amount of tear fluid in the dog has been found to increase. In addition, oxytocin receptors are expressed in the lacrimal gland, and tear volume increased when dogs were exposed to oxytocin eye drops. This suggests that dogs release oxytocin with a positive emotional response when reunited with their owners, which may increase the volume of tear fluid.
演題５：自閉症モデルマーモセットにおける行動研究
中神明子（名古屋大学大学院情報学研究科）
Prof. Young had devoted to unveiling the biological basis of human relationships focusing on pair bonding. Famously, he adopted prairie voles as the model animal. In addition, he, as the director of the Social Translational Research Center at Emory University, aimed to bridge the gap between basic animal research and human studies on autism spectrum disorder (ASD). Once he noted that the common marmoset (Callithrix jacchus), a New World monkey, is one of the few species with oxytocin receptors in the nucleus accumbens, which Dr. Young has proven to be crucial for pair bonding in monogamous prairie voles. This characteristic, combined with the influence of oxytocin on social behavior, is expected to make marmosets a valuable model for studying the neural mechanisms of ASD. To explore this potential, we developed an ASD model in marmosets by administering valproic acid, known to increase autism risk in humans, to pregnant marmosets. Our studies on these ASD model marmosets have revealed significant social deficits across their lifespan. We observed reduced social attention in infants and impaired social cognition in adults, particularly in reciprocity and fairness recognition. These findings strongly support the validity of marmosets as an ASD model, showing correlation between early social attention deficits and adult social cognitive impairments. To advance ASD research and potential therapies, our primate model will contribute to the research of the biological basis of human social relationships that Prof. Young pursued.
質疑とまとめ