Dopamine Signaling and Oxytocin Administration in a Rat Model of Empathy

Abstract

The rat model is commonly used to study prosocial and empathetic behavior. However, the neural underpinnings of such behavior are unknown. We investigated the potential roles of two neurotransmitters, dopamine (DA) and oxytocin (OT), in prosocial behavior of rats. Our first experiment used a Pavlovian association task with two rats to investigate how DA release was modulated by social context. This experiment used fast-scan cyclic voltammetry (FSCV) to measure subsecond DA release in the nucleus accumbens (NAc). Consistent with previous work, cues that predicted reward were associated with increased DA release, and cues that predicted shock inhibited DA release non-discriminately across trial types. However, during shock trials, DA release was modulated by social context in two ways. First, reductions in DA release during shock trials were weaker in the presence of the conspecific, suggesting a consoling effect which was supported by behavioral indicators. Second, DA release during shock trials increased when shock was administered to the conspecific, suggesting that recording rats used the reactions of the conspecific to verify personal safety. We concluded that DA release is modulated by social context in that rats use social cues to optimize predictions about their own well-being. In our second experiment, we investigated the influence of oxytocin on prosocial behavior. Oxytocin was administered intranasally prior to a distress task in which a lever press resulted in reward delivery and one of three additional outcomes: no shock (‘reward-only’), shock to engaged rat (‘shock-self’), or shock to the conspecific (‘shock-other’). Results demonstrated that oxytocin did not significantly increase prosocial behaviors.