Footshock stress reinstates cocaine seeking in rats after extended post-stress delays

Abstract

Rationale

Exposure to footshock stress reinstates drug seeking in rats when tests for reinstatement are conducted immediately after termination of the stressor. It is not known, however, whether footshock is effective in inducing reinstatement if a post-stress delay is imposed before testing for reinstatement.

Objective

The objectives of the study were to determine for how long footshock remains effective in inducing the reinstatement of cocaine seeking if testing is delayed after termination of the stressor and to determine whether the context in which a post-stress delay is carried out influences the magnitude of reinstatement.

Materials and methods

Rats self-administered cocaine (1.0 mg/kg per infusion) for 8–10 days. After extinction, tests for reinstatement by intermittent footshock (20 min; 0.8 mA) were conducted after post-stress delays of up to 60 min. Although footshock was always administered in the self-administration (SA) chamber, delays were given either in the SA chamber or home cage (HC).

Results

Footshock induced reinstatement after post-stress delays of up to 40 min. No differences in responding during tests for reinstatement were observed between animals in the SA chamber and under HC conditions.

Conclusion

Within a limited time window, footshock is effective in reinstating cocaine seeking, when testing is delayed after termination of the stressor. Together with previous work from this laboratory, the findings are consistent with the idea that stress can induce the reinstatement of drug seeking by conditioning excitation to the context in which it is administered and that this conditioned excitation can overcome the inhibitory processes maintaining extinction responding, even after a post-stress delay.