The role of the dopamine D1 receptor in anticipatory pleasure and social play

Social play is a highly rewarding activity seen across mammalian species that is vital for neurobehavioural development. Dysfunctions in social play are seen across psychiatric and neurodevelopmental disorders positing the importance of understanding the neurobiological mechanisms underlying social play. A multitude of neurotransmitter systems have been implicated in social play, with the present study focused on the role of dopamine, specifically the dopamine D1 receptor. Pharmacological manipulations of dopamine and the D1 receptor reveal mixed findings. Given the limited selectivity of pharmacological tools, we explored the role of the dopamine D1 receptor in social play using dopamine D1 mutant (DAD1^-/-) rats which have a genetic reduction in functional D1 receptors. Aligning with the rewarding properties of social play, the present study also examined anticipatory behaviour for the opportunity to engage in social play. Contrary to our predictions, DAD1^-/- mutants initiated and engaged in social play similarly to wildtype controls with only subtle differences in specific elements of play behaviour. Subjects did not differ in 50 kHz vocalisations emitted during play, suggesting similar levels of consummatory pleasure. Although subjects initiated and engaged in play similarly, as predicted, DAD1^-/- mutants displayed deficits in anticipatory behaviour and pleasure for the opportunity to engage in social play. These findings support a prominent role of the D1 receptor in anticipatory behaviour, with further research needed to elucidate its role in social play.