Summary

Numerous preclinical studies have shown that social stress increases vulnerability to the reinforcing effects of cocaine. However, the results obtained are not homogeneous, always observing a subpopulation that does not show such an increase. Using the model of repeated social defeat (SD) in mice, in this work we wanted to behaviorally characterize mice resilient to the increased reinforcing effects of cocaine induced by social stress. We used adult male mice of the C57/BL6 strain that we subjected to the repeated DS protocol and three weeks later, we performed the Place Preference Conditioning (CPL) induced by an ineffective dose of cocaine (1mg/kg). Once this procedure was completed, the striatal levels of interleukin 6 were measured, since social stress produces a neuroinflammation response. No CPL was observed in the control mice, but the defeated animals taken together developed preference. However, this sample could be divided into resilient (did not develop preference) and susceptible (presented CPL) mice. During social defeats, resilient animals spent less time on flight and submission behaviors than those classified as susceptible and exhibited attack behaviors towards the resident mouse, thus manifesting resistance to being defeated. No differences were observed in the neuroinflammation response, probably due to the long period of time since the last social defeat. Our results suggest that an active coping style to social stress will be decisive in protecting the subject from developing a drug use disorder.