Figure 3.

Resilience and vulnerability to 21 days of chronic unpredictable stress (CUS) are marked by specific long-term behavioral, physiological and neuroadaptation in the enkephalinergic (ENKergic) brain circuit. (a) Vulnerable displayed lower duration of social interaction compared with control and resilient individuals. (b) Vulnerable showed lower weight gain compared with resilient individuals. (c) Vulnerable individuals showed higher basal corticosterone compared with control individuals. (d) Vulnerable displayed decreased locomotion as measured by total arm distance in the elevated plus maze (EPM) compared with resilient individuals. (e) Resilient displayed higher exploration as measured by the open-arm time ratio in the EPM compared with control. (f) Enkephalin (ENK) mRNA is reduced only in posterior part of the amygdalar nucleus (BLAp) in vulnerable compared with control and resilient individuals 1 week after the last stress session. In contrast there is no difference between control and resilient individuals. (g) Vulnerable displayed enhanced sucrose consumption compared with control and resilient individuals. (h) No difference in the sucrose preference test between groups. Social interaction was assessed 3 days after the end the CUS. EPM was evaluated 24 h after the social interaction. Sucrose intake and preference tests were performed before (days −3 to −1), during (days 9–10 and 19–20), and after (days 4–6) the CUS. Bars represent mean±SEM; *p<0.05.