P.2.005 The role of adolescent social behaviour in the development of impulse control in rats

Abstract

Adolescence is a critical developmental period, during which maturational changes in the brain are associated with age-specific behavioral characteristics, to facilitate the transition into adulthood. Similar to human children, most young mammals spend a substantial part of postweaning development engaging in play with peers, such as running, chasing, climbing and play fighting. Play experience in a social context is crucial for the development of adaptive socio-affective responses and the acquisition of cognitive skills [1]. Conversely, social deficits are a core symptom of neuropsychiatric disorders that are apparent during childhood and adolescence, such as autism, early-onset schizophrenia, and disruptive behavior disorders. In the present study, we investigated the importance of social interaction during adolescence for the development of impulse control and decision making in rats. To that aim, rats were socially isolated for several weeks during adolescence, subsequently group-housed, and impulsive behavior and decision making were tested in adulthood. Two behavioral dimensions of impulsivity were measured, i.e. inhibitory control using the five-choice serial reaction time task (5-CSRTT) and impulsive choice using the delayed reward task (DRT). In the 5CSRT task, rats are required to wait during an inter-trial interval (ITI) while scanning a horizontal array of five apertures, and to nose poke in the spatial location of a brief visual stimulus in order to earn food reward. The number of responses before the onset of the visual stimulus, i.e. premature responses, is regarded as a measure of impulsivity. In the DRT, rats are faced with a choice between two response options. One option is associated with a small, immediate food reward, whereas the second option results in a larger delayed, but economically optimal food reward. Impulsive choice is associated with a higher preference for the small, immediate reward. Decision making was determined using the rat Gambling Task (rGT). In this paradigm, rats choose among four different options to earn as many sugar pellets as possible within a limited amount of time. Each option is associated with the delivery of a different amount of reward, probability and duration of punishing time-out periods during which reward cannot be earned. Monoaminergic involvement in task performance was investigated using systemic administration of the psychostimulant drug amphetamine, dopamine reuptake inhibitor GBR12909, noradrenaline reuptake inhibitor atomoxetine and serotonin reuptake inhibitor citalopram. The results show that socially isolated rats display hypersensitivity to an impulse control challenge (long intertrial interval), and insensitivity to GBR12909 in the 5CSRTT. No major long-term effects of adolescent social isolation on impulsive choice and decision making were found. These data indicate that adolescent social isolation induces a subtle, but selective impairment in inhibitory control, associated with altered dopamine function in rats. Social interaction during adolescence serves to facilitate the development of inhibitory control capacities.