The relationship between fear extinction and resilience to drug-dependence in rats.

Some individuals recover quickly from stressful events, while others do not; this suggests that there are individual differences in stress resilience. Previous studies in rats have shown that an animal's ability to extinguish conditioned fear can predict their stress resilience. In the present study, we investigated whether rats who are resilient or vulnerable to fear conditioning would consistently show resilient or vulnerable behaviors in other behavioral tests. Male Wistar-Imamichi rats were subjected to a series of behavioral tests, including open field, conditioned place-preference (CPP), forced swim and auditory fear conditioning. The subjects were assigned to one of two different groups: resilient or vulnerable, based on their level of freezing during fear extinction, and their other behavioral phenotypes were then compared. Rats in the resilient group showed faster extinction in the methamphetamine-induced CPP test than rats in the vulnerable group. The results suggest that resilience to stressful events is associated with drug-dependence and that individuals' abilities to recover from stressful situations and drug-dependence may share a common mechanism.