Extinction of traumatic memory in a chronic PTSD-like model is promoted by social buffering phenomenon

Social buffering is a phenomenon by which affiliative social partners mitigate the response to stressors (Kiyokawa et al., 2017). Numerous studies reported that this phenomenon can occur equally among familiar and unfamiliar conspecifics in a variety of species, including laboratory rats (Mikami et al., 2020; Hennessy et al., 2009). Recent studies have reported that social buffering facilitates extinction of aversive memories (Mikami et al., 2020; Mikami et al., 2016). Based on this evidence, the aim of the present study was to evaluate the efficacy of social buffering in the facilitation of traumatic memory extinction in a chronic rat PTSD-like model recently developed in our laboratory (Berardi et al., 2016; Colucci et al., 2020). Specifically, after one week of social isolation and a footshock trauma, rats were exposed to several spaced extinction sessions to mimic the human cognitive behavioral therapy (Colucci et al., 2020). To evaluate the influence of social buffering, extinction sessions were carried out in the presence (or absence) of a social conspecific partner. Our results show that social interaction reduced fear responses (i.e., freezing behaviour) during exposure to the extinction sessions as compared to rats tested in the absence of a conspecific, thus showing the efficacy of social buffering in promoting extinction of traumatic memory in a rat model mimicking PTSD-like symptomatology. Taken together, our findings provide the basis for more mechanistic studies aimed at understanding the neural underpinnings of social buffering of fear and highlight the beneficial effects of group therapy for the treatment of trauma-related disorders, such as PTSD.