Effects of heroin on rat prosocial behavior

Abstract

Opioid use disorders are characterized in part by impairments in social functioning. Previous research indicates that laboratory rats, which are frequently used as animal models of addiction-related behaviors, are capable of prosocial behavior. For example, under normal conditions, when a 'free' rat is placed in the vicinity of rat trapped in a plastic restrainer, the rat will release or 'rescue' the other rat from confinement. The present study was conducted to determine the effects of heroin on prosocial behavior in rats. For 2 weeks, rats were given the opportunity to rescue their cagemate from confinement, and the occurrence of and latency to free the confined rat was recorded. After baseline rescuing behavior was established, rats were randomly selected to self-administer heroin (0.06 mg/kg/infusion i.v.) or sucrose pellets (orally) for 14 days. Next, rats were retested for rescuing behavior once daily for 3 days, during which they were provided with a choice between freeing the trapped cagemate and continuing to self-administer their respective reinforcer. Our results indicate that rats self-administering sucrose continued to rescue their cagemate, whereas heroin rats chose to self-administer heroin and not rescue their cagemate. These findings suggest that rats with a history of heroin self-administration show deficits in prosocial behavior, consistent with specific diagnostic criteria for opioid use disorder. Behavioral paradigms providing a choice between engaging in prosocial behavior and continuing drug use may be useful in modeling and investigating the neural basis of social functioning deficits in opioid addiction.

Keywords: heroin; operant; opioid; prosocial behavior; self-administration; sucrose.

Figure 1.

Photograph of a rescuer rat releasing a trapped rat from a plastic restraint.

Figure 2.

(A) Timeline of different phases of the current study. (B) Number of reinforcers earned during the self-administration phase across the three experimental groups (heroin, n=6), heroin non-patent (n=7), and sucrose (n=7). (C) Rescue rate (defined as the percent of sessions where rescuing behavior was observed) in the each experimental groups during the final 3 test sessions days prior to commencement of self-administration (baseline), and the final 3 tests sessions following the self-administration phase (post self-admin). (D) Number of reinforcers earned by rats in the heroin (n=6) and sucrose (n=7) groups across the 3 test sessions in which animals had simultaneous access to both their respective reinforcer and the trapped rat. E) Total proportion of rescues across the 30 min in the test chamber for each of the reinforcer conditions (n=6 heroin, n=7 heroin non-patent, and n=7 sucrose) before and after the self-administration phases of the experiment.