Stress and relapse to cocaine seeking in the rat: Effects of post-stress delay periods and influence of environmental context

Abstract

Footshock reliably reinstates drug seeking in rats when tests for reinstatement are conducted immediately following termination of the stressor. The present thesis examined whether post-footshock stress delays, and the context in which delays are experienced, affects reinstatement. Rats self-administered cocaine (1.0 mg/kg per infusion) for 8-10 days. Following extinction, tests for reinstatement by intermittent footshock (20 min; 0.8 mA) were conducted following post-stress delays of up to 60 min (experiment 1); delays were experienced in either the self-administration (SA) chamber or homecage (HC) environment (experiment 2). Footshock induced reinstatement following delays of up 40 mins. Animals returned to the HC context during post-stress delays did not exhibit higher levels of responding than animals that remained in the SA chamber. These findings demonstrate that exposure to footshock is capable of inducing reinstatement following extended post-stress delay periods. The effect is consistent with a contextual conditioning account of reinstatement.