Modelling sexual violence in male rats: The sexual aggression test (SxAT)

Sexual assault and rape are crimes that impact victims worldwide. Although the psychosocial and eco-evolutionary factors associated with this antisocial behavior have repeatedly been studied, the underlying neurobiological mechanisms are still unknown mainly due to the lack of an appropriate animal model of sexual aggression (SxA). Here, we established a novel paradigm to provoke and subsequently assess SxA in adult male Wistar rats: the sexual aggression test (SxAT). Briefly, male Wistar rats are sexually aroused by a receptive female, which is exchanged by a non-receptive female immediately after the first intromission. This protocol elicits forced mounting (FM) and aggressive behavior (AB) towards the non-receptive female to different degrees, which can be scored. In a series of experiments we can show that SxA behavior is a relatively stable trait in rats and correlates positively with sexual motivation. Rats with innate abnormal anxiety and aggressive behavior also show abnormal SxA behavior. In addition, central infusion of oxytocin moderately inhibits AB, but increases FM. Finally, we identified the agranular insular cortex to be specifically activated by SxA, and inhibition of this region mildly decreased AB during the SxAT. Altogether, the SxAT is a paradigm that can be readily implemented in behavioral laboratories as a valuable tool to find answers regarding the biological mechanisms underlying SxA in humans, as well as social decision-making in general.