Document Type

Peer-Reviewed Article

Publication Date

3-2012

Abstract

Stress enhances the behavioral effects of cocaine, perhaps via hypothalamic-pituitary-adrenal (HPA) axis activity. Yet, compared to Fischer 344 (F344) rats, Lewis rats have hyporesponsive HPA axis function and more readily acquire cocaine self-administration. We hypothesized that stress would differentially affect cocaine behaviors in these strains. The effects of three stressors on the discriminative stimulus and response rate effects of cocaine were investigated. Rats of both strains were trained to discriminate cocaine (10 mg/kg) from saline using a two-lever, food-reinforced (FR10) procedure. Immediately prior to cumulative dose (1, 3, 10 mg/kg cocaine) test sessions, rats were restrained for 15-min, had 15-min of footshock in a distinct context, or were placed in the shock-paired context. Another set of F344 and Lewis rats were tested similarly except they received vehicle injections to test if stress substituted for cocaine. Most vehicle-tested rats failed to respond after stressor exposures. Among cocaine-tested rats, restraint stress enhanced cocaine’s discriminative stimulus effects in F344 rats. Shock and shock-context increased response rates in Lewis rats. Stress-induced increases in corticosterone levels showed strain differences but did not correlate with behavior. These data suggest that the behavioral effects of cocaine can be differentially affected by stress in a strain-selective manner.

Comments

© 2012 by the authors; licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).

PMCID: PMC4217579

DOI

10.3390/bs2010023

Creative Commons License

Creative Commons Attribution 3.0 License
This work is licensed under a Creative Commons Attribution 3.0 License.

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