Dissociating the role of endocannabinoids in the pleasurable and motivational properties of social play behaviour in rats

Abstract

Social play behaviour is a vigorous form of social interaction, abundant during the juvenile and adolescent phases of life in many mammalian species, including humans. Social play is highly rewarding and it is important for social and cognitive development. Being a rewarding activity, social play can be dissociated in its pleasurable and motivational components. We have previously shown that endocannabinoids modulate the expression of social play behaviour in rats. In the present study, we investigated whether endocannabinoids modulate the motivational and pleasurable properties of social play behaviour, using operant and place conditioning paradigms, respectively. Treatment with the anandamide hydrolysis inhibitor URB597 did not affect operant responding or social play-induced conditioned place preference (CPP) when administered at a dose (0.1 mg/kg) known to increase the expression of social play behaviour, while it modestly reduced operant responding at a higher dose (0.2 mg/kg). The cannabinoid-1 (CB1) receptor antagonist rimonabant reduced operant responding when administered at a dose (1 mg/kg) known to decrease the expression of social play behaviour, although this effect may be secondary to concurrent drug-induced stereotypic behaviours (i.e., grooming and scratching). These data demonstrate that enhancing endocannabinoid levels does not differentially affect the motivational and pleasurable aspects of social play behaviour, whereas CB1 receptor blockade reduces the motivational aspects of social play behaviour, possibly due to response competition. Thus, endocannabinoids likely drive the expression of social play behaviour as a whole, without differentially affecting its motivational or pleasurable properties.

Mu opioid receptors in the medial preoptic area govern social play behavior in adolescent male rats

“…The present study for the first time provides evidence supporting a critical role for the MPOA in rat social play behavior. Given that social play in mammals is a highly rewarding, motivated, affiliative behavior, 11,[68][69][70] and the MPOA is highly conserved (ie, it is neuroanatomically, neurochemically and functionally similar) in birds and mammals, 71,72 we suggest that studies of MPOA, birdsong, and rat play are uncovering a central nucleus that is part of a core, conserved neural circuit across species in which opioids act to stimulate and maintain intrinsically rewarded social behaviors.…”

The neurobiology of social play and its rewarding value in rats

“…Indeed, the recent application of online measurement techniques of brain chemistry, using for example in vivo microdialysis (Bredewold et al, 2015; Robinson et al, 2011), holds considerable promise to increase knowledge in this area. In addition, the application and refinement of place and operant conditioning methods (Achterberg et al, 2016a; Achterberg et al, 2016b; Calcagnetti and Schechter, 1992; Thiel et al, 2008; Trezza et al, 2011a), to investigate the pleasurable and motivational properties of social play, as well as certain cognitive processes involved in this behaviour (Achterberg et al, 2012; Achterberg et al, 2014b), have allowed for the explicit dissection of neural mechanisms underlying sub-components of social play. Although these models have helped us study social reward mechanisms (e.g.…”

“…Using our setup in which rats respond for social play under a PR schedule of reinforcement (Achterberg et al, 2016a; Achterberg et al, 2016b), we showed that treatment with the psychostimulant drugs methylphenidate and cocaine increased responding for social play, but suppressed its expression during reinforced play periods (see above). These effects were further investigated by treating rats with the dopamine reuptake inhibitor GBR12909 and the noradrenaline reuptake inhibitor atomoxetine.…”

“…More recently, we investigated whether endocannabinoids differentially modulate the motivational and pleasurable properties of social play behaviour (Achterberg et al, 2016b). We found that URB597, administered at a dose known to increase the expression of social play behaviour, did not affect social play-induced operant responding or social play-induced conditioned place preference (CPP).…”

“…Recently, we developed an operant conditioning paradigm for social play reward in rats (Achterberg et al, 2016a; Achterberg et al, 2016b). In this setup, rats are trained to lever press for brief episodes of social play behaviour.…”