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


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.


CONCLUSIONS
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.
Centre for the Neurobiology of Stress, Department of Life Science, University of Toronto at Scarborough, Toronto, ON, Canada.
Zenya J
ZJ
Brown
Suzanne
S
Erb
D000818:Animals; D016739:Behavior, Addictive / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D003042:Cocaine / Q000008:administration & dosage / Q000633:toxicity*; D003216:Conditioning, Operant / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004597:Electroshock / Q000009:adverse effects / Q000379:methods*; D005108:Extinction, Psychological / Q000187:drug effects; D015918:Infusion Pumps, Implantable; D008297:Male; D051381:Rats; D020318:Rats, Long-Evans; D012008:Recurrence; D012646:Self Administration; D013315:Stress, Psychological / Q000209:etiology / Q000503:physiopathology* / Q000523:psychology; D013997:Time Factors; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000633:toxicity
D014662:Vasoconstrictor Agents; D003042:Cocaine