Combined maternal separation and limited bedding-nesting increase goal tracking, delay discounting, and impulsive action, and moderate sign-tracking-perseverance associations in male rats.

backgroundExtensive research with rodent models has shown detrimental effects of early-life adversity (ELA) on behavioral (e.g., impulsive behavior, anxiety, and depression) and neurobiological processes (e.g., alterations of neuroendocrine processes and maturation of brain areas). However, heterogeneous methodologies, including types and variations of ELA manipulations could have contributed to inconsistent findings across studies. Recent research indicates that the combination of the two most widely implemented rodent ELA protocols, Maternal Separation (MS) and Limited Bedding/Nesting (LBN), produces consistent and robust behavioral effects. We assessed the effects of combined MS-LBN on four processes linked to both ELA and behavioral disorders in later stages of life: incentive salience of reward cues, and impulsive choice, action, and persistence/perseverance.

methodsSixteen male Sprague Dawley rats were divided in groups of combined MS-LBN during postnatal days 2-21 and without ELA. They were exposed to an Autoshaping Pavlovian conditioning task (AUT), a delay-discounting task (DDT), and acquisition and extinction of a multiple schedule of reinforcement with long and short Variable Intervals (VI) across a span of 18 weeks.

resultsCompared to the No-ELA group, ELA rats displayed higher goal-tracking during the AUT (higher nose-poking in the food-delivery location), higher impulsive choice during test and 7-week re-test of the DDT (preference for the smaller-sooner reinforcer over the larger-later), and less efficient responding during the long-interval schedule of reinforcement (more unnecessary responses per pellet). Associations between autoshaping and reinforcement-schedule performance were identified, with ELA moderating the relationship between sign tracking and efficiency during training and persistence/perseverance during extinction.

conclusionsCombined MS-LBN was associated with task-specific changes in reward-related and impulsive behavior in male rats. These complex patterns of disruptions across behavioral processes adds further support to the notion that combined ELA protocols are promising robust models of adverse rearing in humans, which often entails multiple stressors. CLINICAL TRIAL NUMBER: Not applicable.