Involvement of orexin/hypocretin in the expression of social play behaviour in juvenile rats

Abstract

Biographical note:Christina J. Reppucci: Christina J. Reppucci is a Postdoctoral Researcher in the Neurobiology of Social Behaviour Lab. Her research is focused on delineating the functional neural circuitry underlying motivated behaviours (e.g., social behaviour, feeding behaviour) using system neuroscience approaches, and assessing whether that circuitry is differentially recruited in males and females. Cassandra K. Gergely: Cassanda K. Gergely was an Undergraduate Thesis Student in the Neurobiology of Social Behaviour Lab whose research focused on quantifying the activation of neuropeptide populations during juvenile social play behaviour. Remco Bredewold: Remco Bredewold is a Senior Research Associate in the Neurobiology of Social Behaviour Lab. His research interests focus on the roles of vasopressin and oxytocin in the development of social behaviour. More specifically, he is studying juvenile social play and social recognition. Alexa H. Veenema: Alexa H. Veenema is an Associate Professor of Psychology, and the Director of the Neurobiology of Social Behaviour Lab at Michigan State University. Her research focuses on the neural basis of social behaviour. Understanding the regulation of social behaviour is essential to gain insights in normal social functioning as well as in abnormal social functioning as observed in e.g. autism spectrum disorder, personality disorders, mood and anxiety disorders, and schizophrenia. Her ultimate goal is to understand and treat the causes of social behaviour deficits more effectively.Social play is a highly rewarding and motivated behaviour displayed by juveniles of many mammalian species. We hypothesized that the orexin/hypocretin (ORX) system is involved in the expression of juvenile social play behaviour because this system is interconnected with brain regions that comprise the social behaviour and mesocorticolimbic reward networks. We found that exposure to social play increased recruitment of ORX-A neurons in juvenile male and female rats. Furthermore, central administration of ORX-A decreased social play expression in both sexes, while central blockade of ORX-1 receptors differentially altered social play expression in rats with low versus high baseline levels of social play. Together, our results provided the first evidence of a role for the ORX system in the modulation of juvenile social play behaviour.